Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Francium
open-in-new
<h2 id="characteristics">Characteristics</h2> <p>Francium is one of the most unstable of the naturally occurring elements: its longest-lived isotope, francium-223, has a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of only 22 minutes. The only comparable element is <a href="/facts/Astatine/AlbHPBK5">astatine</a>, whose most stable natural isotope, astatine-219 (the alpha daughter of francium-223), has a half-life of 56 seconds, although synthetic astatine-210 is much longer-lived with a half-life of 8.1 hours.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> All isotopes of francium decay into astatine, <a href="/facts/Radium/VWo5gkzn">radium</a>, or <a href="/facts/Radon/0V9arWKl">radon</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> Francium-223 also has a shorter half-life than the longest-lived isotope of each synthetic element up to and including element 105, <a href="/facts/Dubnium/3CHC1lEt">dubnium</a>.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>Francium is an alkali metal whose chemical properties mostly resemble those of caesium.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> A heavy element with a single <a href="/facts/Valence_electron/mXPA15VP">valence electron</a>,<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> it has the highest <a href="/facts/Equivalent_weight/6Ta7CSs4">equivalent weight</a> of any element.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> Liquid francium—if created—should have a <a href="/facts/Surface_tension/EuluYmSM">surface tension</a> of 0.05092 <a href="/facts/Newton_(unit)/Ral9XgNl">N</a>/m at its melting point.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> Francium's melting point was estimated to be around 8.0 °C (46.4 °F);<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> a value of 27 °C (81 °F) is also often encountered.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> The melting point is uncertain because of the element's extreme rarity and <a href="/facts/Radioactivity/Ya6FVjt4">radioactivity</a>; a different extrapolation based on <a href="/facts/Dmitri_Mendeleev/xdouRrx8">Dmitri Mendeleev</a>'s method gave 20 ± 1.5 °C (68.0 ± 2.7 °F). A calculation based on the melting temperatures of binary ionic crystals gives 24.861 ± 0.517 °C (76.750 ± 0.931 °F).<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> The estimated boiling point of 620 °C (1,148 °F) is also uncertain; the estimates 598 °C (1,108 °F) and 677 °C (1,251 °F), as well as the extrapolation from Mendeleev's method of 640 °C (1,184 °F), have also been suggested.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> The density of francium is expected to be around 2.48 g/cm3 (Mendeleev's method extrapolates 2.4 g/cm3).<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p><p><a href="/facts/Linus_Pauling/cBNBzs5c">Linus Pauling</a> estimated the <a href="/facts/Electronegativity/H7Vq7Uah">electronegativity</a> of francium at 0.7 on the <a href="/facts/Pauling_scale/H7Vq7Uah">Pauling scale</a>, the same as caesium;<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> the value for caesium has since been refined to 0.79, but there are no experimental data to allow a refinement of the value for francium.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> Francium has a slightly higher <a href="/facts/Ionization_energy/lezUajfA">ionization energy</a> than caesium,<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> 392.811(4) kJ/mol as opposed to 375.7041(2) kJ/mol for caesium, as would be expected from <a href="/facts/Relativistic_quantum_chemistry/8A1se1CS">relativistic effects</a>, and this would imply that caesium is the less electronegative of the two. Francium should also have a higher <a href="/facts/Electron_affinity/1mf4A396">electron affinity</a> than caesium and the Fr− ion should be more <a href="/facts/Polarizability/0XRkXwUu">polarizable</a> than the Cs− ion.<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> </p> <h2 id="compounds">Compounds</h2> <p>As a result of francium's instability, its salts are only known to a small extent. Francium <a href="/facts/Coprecipitation/K3oC2U1X">coprecipitates</a> with several caesium <a href="/facts/Salt_(chemistry)/lsSKwGpn">salts</a>, such as <a href="/facts/Caesium_perchlorate/k4RkdUFE">caesium perchlorate</a>, which results in small amounts of francium perchlorate. This coprecipitation can be used to isolate francium, by adapting the radiocaesium coprecipitation method of <a href="/facts/Lawrence_E._Glendenin/pp0h2sy4">Lawrence E. Glendenin</a> and C. M. Nelson. It will additionally coprecipitate with many other caesium salts, including the <a href="/facts/Iodate/n60p0YSa">iodate</a>, the <a href="/facts/Picrate/q8JfQDUp">picrate</a>, the <a href="/facts/Tartrate/6gbDbxIP">tartrate</a> (also <a href="/facts/Rubidium/KDHSe2HM">rubidium</a> tartrate), the chloroplatinate, and the <a href="/facts/Silicotungstate/4h1ytCa2">silicotungstate</a>. It also coprecipitates with <a href="/facts/Silicotungstic_acid/4h1ytCa2">silicotungstic acid</a>, and with <a href="/facts/Perchloric_acid/gjhK386J">perchloric acid</a>, without another alkali metal as a <a href="/facts/Carrier_(chemistry)/K3oC2U1X">carrier</a>, which leads to other methods of separation.<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a><a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> </p> <h3>Francium perchlorate</h3> <p>Francium perchlorate is produced by the reaction of <a href="/facts/Francium_chloride/wL4VzCrD">francium chloride</a> and <a href="/facts/Sodium_perchlorate/crnf8NU1">sodium perchlorate</a>. The francium perchlorate <a href="/facts/Coprecipitation/K3oC2U1X">coprecipitates</a> with <a href="/facts/Caesium_perchlorate/k4RkdUFE">caesium perchlorate</a>.<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> This coprecipitation can be used to isolate francium, by adapting the radiocaesium coprecipitation method of <a href="/facts/Lawrence_E._Glendenin/pp0h2sy4">Lawrence E. Glendenin</a> and C. M. Nelson. However, this method is unreliable in separating <a href="/facts/Thallium/v35pGMJB">thallium</a>, which also coprecipitates with caesium.<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a> Francium perchlorate's <a href="/facts/Entropy/s52IXeFz">entropy</a> is expected to be 42.7 <a href="/facts/Entropy_unit/s52IXeFz">e.u</a><a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a> (178.7 J mol−1 K−1). </p> <h3>Francium halides</h3> <p>Francium halides are all soluble in water and are expected to be white solids. They are expected to be produced by the reaction of the corresponding <a href="/facts/Halogen/YeFgWHeA">halogens</a>. For example, francium chloride would be produced by the reaction of francium and <a href="/facts/Chlorine/y27UwYBM">chlorine</a>. Francium chloride has been studied as a pathway to separate francium from other elements, by using the high <a href="/facts/Vapour_pressure/whrEr96T">vapour pressure</a> of the compound, although francium fluoride would have a higher vapour pressure.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> </p> <h3>Other compounds</h3> <p>Francium nitrate, sulfate, hydroxide, carbonate, acetate, and oxalate, are all soluble in water, while the <a href="/facts/Iodate/n60p0YSa">iodate</a>, <a href="/facts/Picrate/q8JfQDUp">picrate</a>, <a href="/facts/Tartrate/6gbDbxIP">tartrate</a>, <a href="/facts/Chloroplatinic_acid/3F3cuA1b">chloroplatinate</a>, and <a href="/facts/Silicotungstate/4h1ytCa2">silicotungstate</a> are insoluble. The insolubility of these compounds are used to extract francium from other radioactive products, such as <a href="/facts/Zirconium/y7gsoQFz">zirconium</a>, <a href="/facts/Niobium/3zNI8AKp">niobium</a>, <a href="/facts/Molybdenum/RX6vp2bF">molybdenum</a>, <a href="/facts/Tin/obW9mqc3">tin</a>, <a href="/facts/Antimony/YsA7lVgT">antimony</a>, the method mentioned in the section above.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> Francium oxide is believed to disproportionate to the peroxide and francium metal.<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> The CsFr molecule is predicted to have the heavier element (francium) at the negative end of the dipole, unlike all known heterodiatomic alkali metal molecules. Francium <a href="/facts/Superoxide/2X2sQocn">superoxide</a> (FrO2) is expected to have a more <a href="/facts/Covalent/EzMLf3Pz">covalent</a> character than its lighter <a href="/facts/Congener_(chemistry)/8qy2rvGG">congeners</a>; this is attributed to the 6p electrons in francium being more involved in the francium–oxygen bonding.<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> The relativistic destabilisation of the 6p3/2 spinor may make francium compounds in oxidation states higher than +1 possible, such as [FrVF6]−; but this has not been experimentally confirmed.<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a> </p> <h2 id="isotopes">Isotopes</h2> <p class="note">Main article: <a href="/facts/Isotopes_of_francium/gc1IXyua">Isotopes of francium</a></p> <p>There are 37 known isotopes of francium ranging in <a href="/facts/Atomic_mass/J1FJY9MV">atomic mass</a> from 197 to 233.<a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a> Francium has seven <a href="/facts/Metastability/H72SMWof">metastable</a> <a href="/facts/Nuclear_isomer/L8DHcqnk">nuclear isomers</a>.<a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a> Francium-223 and francium-221 are the only isotopes that occur in nature, with the former being far more common.<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a> </p><p>Francium-223 is the most stable isotope, with a half-life of 21.8 minutes,<a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a> and it is highly unlikely that an isotope of francium with a longer half-life will ever be discovered or synthesized.<a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a> Francium-223 is a fifth product of the <a href="/facts/Uranium-235/pe0RznDM">uranium-235</a> decay series as a daughter isotope of <a href="/facts/Actinium-227/vnv59EsB">actinium-227</a>; <a href="/facts/Thorium-227/lRb3opzg">thorium-227</a> is the more common daughter.<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a> Francium-223 then decays into radium-223 by <a href="/facts/Beta_decay/vxTBlckp">beta decay</a> (1.149 MeV <a href="/facts/Decay_energy/g4wDGC8r">decay energy</a>), with a minor (0.006%) <a href="/facts/Alpha_decay/rCsHNIUE">alpha decay</a> path to astatine-219 (5.4 MeV decay energy).<a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a> </p><p>Francium-221 has a half-life of 4.8 minutes.<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a> It is the ninth product of the <a href="/facts/Neptunium/pwp7Yvds">neptunium</a> decay series as a daughter isotope of <a href="/facts/Actinium-225/2fBD0uCw">actinium-225</a>.<a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a> Francium-221 then decays into astatine-217 by alpha decay (6.457 MeV decay energy).<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a> Although all primordial 237Np is <a href="/facts/Extinct_radionuclide/dmr9aTBW">extinct</a>, the neptunium decay series continues to exist naturally in tiny traces due to (n,2n) knockout reactions in natural 238U.<a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a> Francium-222, with a half-life of 14 minutes, may be produced as a result of the beta decay of natural <a href="/facts/Radon-222/FTWdEQn0">radon-222</a>; this process has nonetheless not yet been observed,<a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a> and it is unknown whether this process is energetically possible.<a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a> </p><p>The least stable <a href="/facts/Ground_state/ML7cfCug">ground state</a> isotope is francium-215, with a half-life of 90 ns:<a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a> it undergoes a 9.54 MeV alpha decay to astatine-211.<a class="footnote-ref" id="fnref:46" href="#fn:46"><sup>46</sup></a> </p> <h2 id="applications">Applications</h2> <p>Due to its instability and rarity, there are no commercial applications for francium.<a class="footnote-ref" id="fnref:47" href="#fn:47"><sup>47</sup></a><a class="footnote-ref" id="fnref:48" href="#fn:48"><sup>48</sup></a><a class="footnote-ref" id="fnref:49" href="#fn:49"><sup>49</sup></a><a class="footnote-ref" id="fnref:50" href="#fn:50"><sup>50</sup></a> It has been used for research purposes in the fields of <a href="/facts/Chemistry/SrNqkGVm">chemistry</a><a class="footnote-ref" id="fnref:51" href="#fn:51"><sup>51</sup></a> and of <a href="/facts/Atom/FoQ4kGN5">atomic structure</a>. Its use as a potential diagnostic aid for various <a href="/facts/Cancer/PVW6n1D0">cancers</a> has also been explored,<a class="footnote-ref" id="fnref:52" href="#fn:52"><sup>52</sup></a> but this application has been deemed impractical.<a class="footnote-ref" id="fnref:53" href="#fn:53"><sup>53</sup></a> </p><p>Francium's ability to be synthesized, trapped, and cooled, along with its relatively simple <a href="/facts/Atom/FoQ4kGN5">atomic structure</a>, has made it the subject of specialized <a href="/facts/Spectroscopy/mj71FuNK">spectroscopy</a> experiments. These experiments have led to more specific information regarding <a href="/facts/Energy_level/66x51Khc">energy levels</a> and the <a href="/facts/Coupling_constant/Queop1TR">coupling constants</a> between <a href="/facts/Subatomic_particle/tMEzcTWQ">subatomic particles</a>.<a class="footnote-ref" id="fnref:54" href="#fn:54"><sup>54</sup></a> Studies on the light emitted by <a href="/facts/Optical_tweezers/wsPxwmX6">laser-trapped</a> francium-210 ions have provided accurate data on transitions between atomic energy levels which are fairly similar to those predicted by <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum theory</a>.<a class="footnote-ref" id="fnref:55" href="#fn:55"><sup>55</sup></a> Francium is a prospective candidate for searching for <a href="/facts/CP_violation/Nu5lCsPI">CP violation</a>.<a class="footnote-ref" id="fnref:56" href="#fn:56"><sup>56</sup></a> </p> <h2 id="history">History</h2> <p>As early as 1870, chemists thought that there should be an alkali metal beyond <a href="/facts/Caesium/dXKN1S5k">caesium</a>, with an atomic number of 87.<a class="footnote-ref" id="fnref:57" href="#fn:57"><sup>57</sup></a> It was then referred to by the provisional name <i><a href="/facts/Mendeleev%2527s_predicted_elements/C4vgW0uy">eka-caesium</a></i>.<a class="footnote-ref" id="fnref:58" href="#fn:58"><sup>58</sup></a> </p> <h3>Erroneous and incomplete discoveries</h3> <p>In 1914, <a href="/facts/Stefan_Meyer_(physicist)/I7t9MjBG">Stefan Meyer</a>, Viktor F. Hess, and <a href="/facts/Friedrich_Paneth/fsgC4WC8">Friedrich Paneth</a> (working in Vienna) made measurements of alpha radiation from various substances, including 227Ac. They observed the possibility of a minor alpha branch of this nuclide, though follow-up work could not be done due to the outbreak of <a href="/facts/World_War_I/vITTUanQ">World War I</a>. Their observations were not precise and sure enough for them to announce the discovery of element 87, though it is likely that they did indeed observe the decay of 227Ac to 223Fr.<a class="footnote-ref" id="fnref:59" href="#fn:59"><sup>59</sup></a> </p><p>Soviet chemist Dmitry Dobroserdov was the first scientist to claim to have found eka-caesium, or francium. In 1925, he observed weak radioactivity in a sample of <a href="/facts/Potassium/FWPwS7Rj">potassium</a>, another alkali metal, and incorrectly concluded that eka-caesium was contaminating the sample (the radioactivity from the sample was from the naturally occurring potassium radioisotope, <a href="/facts/Potassium-40/RMnkrhvc">potassium-40</a>).<a class="footnote-ref" id="fnref:60" href="#fn:60"><sup>60</sup></a> He then published a thesis on his predictions of the properties of eka-caesium, in which he named the element <i>russium</i> after his home country.<a class="footnote-ref" id="fnref:61" href="#fn:61"><sup>61</sup></a> Shortly thereafter, Dobroserdov began to focus on his teaching career at the Polytechnic Institute of <a href="/facts/Odesa/4Luy5oB3">Odesa</a>, and he did not pursue the element further.<a class="footnote-ref" id="fnref:62" href="#fn:62"><sup>62</sup></a> </p><p>The following year, English chemists Gerald J. F. Druce and Frederick H. Loring analyzed <a href="/facts/X-ray/wseP79cN">X-ray</a> photographs of <a href="/facts/Manganese(II)_sulfate/RVBG26R6">manganese(II) sulfate</a>.<a class="footnote-ref" id="fnref:63" href="#fn:63"><sup>63</sup></a> They observed spectral lines which they presumed to be of eka-caesium. They announced their discovery of element 87 and proposed the name <i>alkalinium</i>, as it would be the heaviest alkali metal.<a class="footnote-ref" id="fnref:64" href="#fn:64"><sup>64</sup></a> </p><p>In 1930, <a href="/facts/Fred_Allison/Sc0u81G7">Fred Allison</a> of the <a href="/facts/Alabama_Polytechnic_Institute/kz4YvffX">Alabama Polytechnic Institute</a> claimed to have discovered element 87 (in addition to 85) when analyzing <a href="/facts/Pollucite/qClNH6uX">pollucite</a> and <a href="/facts/Lepidolite/tp55Ysme">lepidolite</a> using his <a href="/facts/Magneto-optic_effect/kJnv2D05">magneto-optical</a> machine. Allison requested that it be named <i>virginium</i> after his home state of <a href="/facts/Virginia/g2kucGdn">Virginia</a>, along with the symbols Vi and Vm.<a class="footnote-ref" id="fnref:65" href="#fn:65"><sup>65</sup></a><a class="footnote-ref" id="fnref:66" href="#fn:66"><sup>66</sup></a> In 1934, H.G. MacPherson of <a href="/facts/University_of_California%2c_Berkeley/MXVEjklr">UC Berkeley</a> disproved the effectiveness of Allison's device and the validity of his discovery.<a class="footnote-ref" id="fnref:67" href="#fn:67"><sup>67</sup></a> </p><p>In 1936, Romanian physicist <a href="/facts/Horia_Hulubei/XMNRAuDT">Horia Hulubei</a> and his French colleague <a href="/facts/Yvette_Cauchois/5aE0B0xY">Yvette Cauchois</a> also analyzed pollucite, this time using their high-resolution X-ray apparatus.<a class="footnote-ref" id="fnref:68" href="#fn:68"><sup>68</sup></a> They observed several weak emission lines, which they presumed to be those of element 87. Hulubei and Cauchois reported their discovery and proposed the name <i>moldavium</i>, along with the symbol Ml, after <a href="/facts/Moldavia/KDqRzNHf">Moldavia</a>, the Romanian province where Hulubei was born.<a class="footnote-ref" id="fnref:69" href="#fn:69"><sup>69</sup></a> In 1937, Hulubei's work was criticized by American physicist F. H. Hirsh Jr., who rejected Hulubei's research methods. Hirsh was certain that eka-caesium would not be found in nature, and that Hulubei had instead observed <a href="/facts/Mercury_(element)/WlxfoHva">mercury</a> or <a href="/facts/Bismuth/75FLjkoX">bismuth</a> X-ray lines. Hulubei insisted that his X-ray apparatus and methods were too accurate to make such a mistake. Because of this, <a href="/facts/Jean_Baptiste_Perrin/M81KaotS">Jean Baptiste Perrin</a>, <a href="/facts/Nobel_Prize/3z1Y3oFL">Nobel Prize</a> winner and Hulubei's mentor, endorsed moldavium as the true eka-caesium over <a href="/facts/Marguerite_Perey/FY8bIRuk">Marguerite Perey</a>'s recently discovered francium. Perey took pains to be accurate and detailed in her criticism of Hulubei's work, and finally she was credited as the sole discoverer of element 87.<a class="footnote-ref" id="fnref:70" href="#fn:70"><sup>70</sup></a> All other previous purported discoveries of element 87 were ruled out due to francium's very limited half-life.<a class="footnote-ref" id="fnref:71" href="#fn:71"><sup>71</sup></a> </p> <h3>Perey's analysis</h3> <p>Eka-caesium was discovered on January 7, 1939, by <a href="/facts/Marguerite_Perey/FY8bIRuk">Marguerite Perey</a> of the <a href="/facts/Curie_Institute_(Paris)/lvzkmu8g">Curie Institute</a> in Paris,<a class="footnote-ref" id="fnref:72" href="#fn:72"><sup>72</sup></a> when she purified a sample of <a href="/facts/Actinium/GMQtJ4Gm">actinium</a>-227 which had been reported to have a decay energy of 220 keV. Perey noticed decay particles with an energy level below 80 keV. Perey thought this decay activity might have been caused by a previously unidentified decay product, one which was separated during purification, but emerged again out of the pure actinium-227. Various tests eliminated the possibility of the unknown element being <a href="/facts/Thorium/ysdWH470">thorium</a>, radium, <a href="/facts/Lead/EYljasJN">lead</a>, bismuth, or <a href="/facts/Thallium/v35pGMJB">thallium</a>. The new product exhibited chemical properties of an alkali metal (such as coprecipitating with caesium salts), which led Perey to believe that it was element 87, produced by the <a href="/facts/Alpha_decay/rCsHNIUE">alpha decay</a> of actinium-227.<a class="footnote-ref" id="fnref:73" href="#fn:73"><sup>73</sup></a> Perey then attempted to determine the proportion of <a href="/facts/Beta_decay/vxTBlckp">beta decay</a> to alpha decay in actinium-227. Her first test put the alpha branching at 0.6%, a figure which she later revised to 1%.<a class="footnote-ref" id="fnref:74" href="#fn:74"><sup>74</sup></a> </p><p>Perey named the new isotope <i>actinium-K</i> (it is now referred to as francium-223)<a class="footnote-ref" id="fnref:75" href="#fn:75"><sup>75</sup></a> and in 1946, she proposed the name <i>catium</i> (Cm) for her newly discovered element, as she believed it to be the most <a href="/facts/Electronegativity/H7Vq7Uah">electropositive</a> <a href="/facts/Cation/wrbwhF3z">cation</a> of the elements. <a href="/facts/Ir%25C3%25A8ne_Joliot-Curie/rhBlqKxf">Irène Joliot-Curie</a>, one of Perey's supervisors, opposed the name due to its connotation of <i>cat</i> rather than <i>cation</i>; furthermore, the symbol coincided with that which had since been assigned to <a href="/facts/Curium/LMyWXg8l">curium</a>.<a class="footnote-ref" id="fnref:76" href="#fn:76"><sup>76</sup></a> Perey then suggested <i>francium</i>, after France. This name was officially adopted by the <a href="/facts/International_Union_of_Pure_and_Applied_Chemistry/2AV6myCK">International Union of Pure and Applied Chemistry</a> (IUPAC) in 1949,<a class="footnote-ref" id="fnref:77" href="#fn:77"><sup>77</sup></a> becoming the second element after <a href="/facts/Gallium/EucevDs9">gallium</a> to be named after France. It was assigned the symbol Fa, but it was revised to the current Fr shortly thereafter.<a class="footnote-ref" id="fnref:78" href="#fn:78"><sup>78</sup></a> Francium was the last element discovered in nature, rather than synthesized, following <a href="/facts/Hafnium/rBNnlxDS">hafnium</a> and <a href="/facts/Rhenium/TzyqJYEn">rhenium</a>.<a class="footnote-ref" id="fnref:79" href="#fn:79"><sup>79</sup></a> Further research into francium's structure was carried out by, among others, Sylvain Lieberman and his team at <a href="/facts/CERN/y1gwRchm">CERN</a> in the 1970s and 1980s.<a class="footnote-ref" id="fnref:80" href="#fn:80"><sup>80</sup></a> </p> <h2 id="occurrence">Occurrence</h2> <p>223Fr is the result of the alpha decay of <a href="/facts/Isotopes_of_actinium/vnv59EsB">227Ac</a> and can be found in trace amounts in <a href="/facts/Uranium/n2sGWBzU">uranium</a> <a href="/facts/Mineral/LkUFbNmv">minerals</a>.<a class="footnote-ref" id="fnref:81" href="#fn:81"><sup>81</sup></a> In a given sample of uranium, there is estimated to be only one francium atom for every 1 × 1018 uranium atoms.<a class="footnote-ref" id="fnref:82" href="#fn:82"><sup>82</sup></a> Only about 1 ounce (28 g) of francium is present naturally in the earth's crust.<a class="footnote-ref" id="fnref:83" href="#fn:83"><sup>83</sup></a> </p> <h2 id="production">Production</h2> <p>Francium can be synthesized by a <a href="/facts/Nuclear_fusion/hP0gLDqj">fusion</a> reaction when a gold-197 target is bombarded with a beam of oxygen-18 atoms from a <a href="/facts/Linear_accelerator/GIz6Uc4x">linear accelerator</a> in a process originally developed at the physics department of the <a href="/facts/State_University_of_New_York_at_Stony_Brook/4LwsKo7h">State University of New York at Stony Brook</a> in 1995.<a class="footnote-ref" id="fnref:84" href="#fn:84"><sup>84</sup></a> Depending on the energy of the oxygen beam, the reaction can yield francium isotopes with masses of 209, 210, and 211. </p> 197Au + 18O → 209Fr + 6 n 197Au + 18O → 210Fr + 5 n 197Au + 18O → 211Fr + 4 n <p>The francium atoms leave the gold target as ions, which are neutralized by collision with <a href="/facts/Yttrium/BlX6rj99">yttrium</a> and then isolated in a <a href="/facts/Magneto-optical_trap/thqk1QsG">magneto-optical trap</a> (MOT) in a gaseous unconsolidated state.<a class="footnote-ref" id="fnref:85" href="#fn:85"><sup>85</sup></a> Although the atoms only remain in the trap for about 30 seconds before escaping or undergoing nuclear decay, the process supplies a continual stream of fresh atoms. The result is a <a href="/facts/Steady_state/qgrL4BNs">steady state</a> containing a fairly constant number of atoms for a much longer time.<a class="footnote-ref" id="fnref:86" href="#fn:86"><sup>86</sup></a> The original apparatus could trap up to a few thousand atoms, while a later improved design could trap over 300,000 at a time.<a class="footnote-ref" id="fnref:87" href="#fn:87"><sup>87</sup></a> Sensitive measurements of the light emitted and absorbed by the trapped atoms provided the first experimental results on various transitions between atomic energy levels in francium. Initial measurements show very good agreement between experimental values and calculations based on quantum theory. The research project using this production method relocated to <a href="/facts/TRIUMF/CND7CLBL">TRIUMF</a> in 2012, where over 106 francium atoms have been held at a time, including large amounts of 209Fr in addition to 207Fr and 221Fr.<a class="footnote-ref" id="fnref:88" href="#fn:88"><sup>88</sup></a><a class="footnote-ref" id="fnref:89" href="#fn:89"><sup>89</sup></a> </p><p>Other synthesis methods include bombarding radium with neutrons, and bombarding thorium with protons, <a href="/facts/Deuterium/Bv4wfCkw">deuterons</a>, or <a href="/facts/Helium/yRul93TG">helium</a> <a href="/facts/Ion/3bePpDna">ions</a>.<a class="footnote-ref" id="fnref:90" href="#fn:90"><sup>90</sup></a> </p><p>223Fr can also be isolated from samples of its parent 227Ac, the francium being milked via elution with NH4Cl–CrO3 from an actinium-containing cation exchanger and purified by passing the solution through a <a href="/facts/Silicon_dioxide/A3WILp6J">silicon dioxide</a> compound loaded with <a href="/facts/Barium_sulfate/QrjdoS1k">barium sulfate</a>.<a class="footnote-ref" id="fnref:91" href="#fn:91"><sup>91</sup></a> </p><p>In 1996, the Stony Brook group trapped 3000 atoms in their MOT, which was enough for a video camera to capture the light given off by the atoms as they fluoresce.<a class="footnote-ref" id="fnref:92" href="#fn:92"><sup>92</sup></a> Francium has not been synthesized in amounts large enough to weigh.<a class="footnote-ref" id="fnref:93" href="#fn:93"><sup>93</sup></a><a class="footnote-ref" id="fnref:94" href="#fn:94"><sup>94</sup></a><a class="footnote-ref" id="fnref:95" href="#fn:95"><sup>95</sup></a> </p> <h2 id="notes">Notes</h2> <h2 id="external-links">External links</h2> <ul><li><a href="http://www.periodicvideos.com/videos/087.htm">Francium</a> at <i><a href="/facts/The_Periodic_Table_of_Videos/vC5kbN0M">The Periodic Table of Videos</a></i> (University of Nottingham)</li> <li><a href="http://www.webelements.com/webelements/elements/text/Fr/index.html">WebElements.com – Francium</a></li> <li><a href="https://web.archive.org/web/19981203125538/http://fr.physics.sunysb.edu/francium_news/frconten.htm">Stony Brook University Physics Dept.</a></li> <li><a href="/facts/Eric_Scerri/5a4eoMMH">Scerri, Eric</a> (2013). <i>A Tale of Seven Elements</i>, Oxford University Press, Oxford, <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 9780195391312</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Guruge, Amila Ruwan (January 25, 2023). "Francium". Chemical and Process Engineering. Retrieved February 28, 2023. <a href="https://www.arhse.com/francium/" target="_blank">https://www.arhse.com/francium/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Perey, M. (October 1, 1939). "L'élément 87 : AcK, dérivé de l'actinium". Journal de Physique et le Radium (in French). 10 (10): 435–438. doi:10.1051/jphysrad:019390010010043500. ISSN 0368-3842. <a href="https://hal.archives-ouvertes.fr/jpa-00233698/document" target="_blank">https://hal.archives-ouvertes.fr/jpa-00233698/document</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Some synthetic elements, like technetium and plutonium, have later been found in nature. <a href="/wiki/Technetium" target="_blank">/wiki/Technetium</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Orozco, Luis A. (2003). "Francium". Chemical and Engineering News. 81 (36): 159. doi:10.1021/cen-v081n036.p159. <a href="http://pubs.acs.org/cen/80th/francium.html" target="_blank">http://pubs.acs.org/cen/80th/francium.html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Price, Andy (December 20, 2004). "Francium". Retrieved February 19, 2012. <a href="http://www.andyscouse.com/pages/francium.htm" target="_blank">http://www.andyscouse.com/pages/francium.htm</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Price, Andy (December 20, 2004). "Francium". Retrieved February 19, 2012. <a href="http://www.andyscouse.com/pages/francium.htm" target="_blank">http://www.andyscouse.com/pages/francium.htm</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Winter, Mark. "Electron Configuration". Francium. The University of Sheffield. Retrieved April 18, 2007. <a href="http://www.webelements.com/webelements/elements/text/Fr/eneg.html" target="_blank">http://www.webelements.com/webelements/elements/text/Fr/eneg.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Kozhitov, L. V.; Kol'tsov, V. B.; Kol'tsov, A. V. (2003). "Evaluation of the Surface Tension of Liquid Francium". Inorganic Materials. 39 (11): 1138–1141. doi:10.1023/A:1027389223381. S2CID 97764887. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Lavrukhina, Avgusta Konstantinovna; Pozdnyakov, Aleksandr Aleksandrovich (1970). Analytical Chemistry of Technetium, Promethium, Astatine, and Francium. Translated by R. Kondor. Ann Arbor–Humphrey Science Publishers. p. 269. ISBN 978-0-250-39923-9. <a href="978-0-250-39923-9" target="_blank">978-0-250-39923-9</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Oshchapovskii, V. V. (2014). "A New Method of Calculation of the Melting Temperatures of Crystals of Group 1A Metal Halides and Francium Metal". Russian Journal of Inorganic Chemistry. 59 (6): 561–567. doi:10.1134/S0036023614060163. S2CID 98622837. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Lavrukhina, Avgusta Konstantinovna; Pozdnyakov, Aleksandr Aleksandrovich (1970). Analytical Chemistry of Technetium, Promethium, Astatine, and Francium. Translated by R. Kondor. Ann Arbor–Humphrey Science Publishers. p. 269. ISBN 978-0-250-39923-9. <a href="978-0-250-39923-9" target="_blank">978-0-250-39923-9</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Kozhitov, L. V.; Kol'tsov, V. B.; Kol'tsov, A. V. (2003). "Evaluation of the Surface Tension of Liquid Francium". Inorganic Materials. 39 (11): 1138–1141. doi:10.1023/A:1027389223381. S2CID 97764887. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Lavrukhina, Avgusta Konstantinovna; Pozdnyakov, Aleksandr Aleksandrovich (1970). Analytical Chemistry of Technetium, Promethium, Astatine, and Francium. Translated by R. Kondor. Ann Arbor–Humphrey Science Publishers. p. 269. ISBN 978-0-250-39923-9. <a href="978-0-250-39923-9" target="_blank">978-0-250-39923-9</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Pauling, Linus (1960). The Nature of the Chemical Bond (Third ed.). Cornell University Press. p. 93. ISBN 978-0-8014-0333-0. {{cite book}}: ISBN / Date incompatibility (help) <a href="978-0-8014-0333-0" target="_blank">978-0-8014-0333-0</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Allred, A. L. (1961). "Electronegativity values from thermochemical data". J. Inorg. Nucl. Chem. 17 (3–4): 215–221. doi:10.1016/0022-1902(61)80142-5. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Andreev, S.V.; Letokhov, V.S.; Mishin, V.I. (1987). "Laser resonance photoionization spectroscopy of Rydberg levels in Fr". Physical Review Letters. 59 (12): 1274–76. Bibcode:1987PhRvL..59.1274A. doi:10.1103/PhysRevLett.59.1274. PMID 10035190. <a href="/wiki/Physical_Review_Letters" target="_blank">/wiki/Physical_Review_Letters</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Thayer, John S. (2010). "Chap.10 Relativistic Effects and the Chemistry of the Heavier Main Group Elements". Relativistic Methods for Chemists. Springer. p. 81. doi:10.1007/978-1-4020-9975-5_2. ISBN 978-1-4020-9975-5. <a href="978-1-4020-9975-5" target="_blank">978-1-4020-9975-5</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Hyde, E. K. (1952). "Radiochemical Methods for the Isolation of Element 87 (Francium)". J. Am. Chem. Soc. 74 (16): 4181–4184. Bibcode:1952JAChS..74.4181H. doi:10.1021/ja01136a066. hdl:2027/mdp.39015086483156. S2CID 95854270. <a href="/wiki/J._Am._Chem._Soc." target="_blank">/wiki/J._Am._Chem._Soc.</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>E. N K. Hyde Radiochemistry of Francium, Subcommittee on Radiochemistry, National Academy of Sciences-National Research Council; available from the Office of Technical Services, Dept. of Commerce, 1960. <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>E. N K. Hyde Radiochemistry of Francium, Subcommittee on Radiochemistry, National Academy of Sciences-National Research Council; available from the Office of Technical Services, Dept. of Commerce, 1960. <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>E. N K. Hyde Radiochemistry of Francium, Subcommittee on Radiochemistry, National Academy of Sciences-National Research Council; available from the Office of Technical Services, Dept. of Commerce, 1960. <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Lavrukhina, Avgusta Konstantinovna; Pozdnyakov, Aleksandr Aleksandrovich (1970). Analytical Chemistry of Technetium, Promethium, Astatine, and Francium. Translated by R. Kondor. Ann Arbor–Humphrey Science Publishers. p. 269. ISBN 978-0-250-39923-9. <a href="978-0-250-39923-9" target="_blank">978-0-250-39923-9</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Lavrukhina, Avgusta Konstantinovna; Pozdnyakov, Aleksandr Aleksandrovich (1970). Analytical Chemistry of Technetium, Promethium, Astatine, and Francium. Translated by R. Kondor. Ann Arbor–Humphrey Science Publishers. p. 269. ISBN 978-0-250-39923-9. <a href="978-0-250-39923-9" target="_blank">978-0-250-39923-9</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>Lavrukhina, Avgusta Konstantinovna; Pozdnyakov, Aleksandr Aleksandrovich (1970). Analytical Chemistry of Technetium, Promethium, Astatine, and Francium. Translated by R. Kondor. Ann Arbor–Humphrey Science Publishers. p. 269. ISBN 978-0-250-39923-9. <a href="978-0-250-39923-9" target="_blank">978-0-250-39923-9</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>Hyde, E. K.; Ghiorso, A.; Seaborg, G. T. (October 10, 1949). Low Mass Francium and Emanation Isotopes of High Alpha Stability (Report). Berkeley, CA: UC Radiation Laboratory. p. 9. UCRL-409. <a href="/wiki/Albert_Ghiorso" target="_blank">/wiki/Albert_Ghiorso</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>Thayer, John S. (2010). "Chap.10 Relativistic Effects and the Chemistry of the Heavier Main Group Elements". Relativistic Methods for Chemists. Springer. p. 81. doi:10.1007/978-1-4020-9975-5_2. ISBN 978-1-4020-9975-5. <a href="978-1-4020-9975-5" target="_blank">978-1-4020-9975-5</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Cao, Chang-Su; Hu, Han-Shi; Schwarz, W. H. Eugen; Li, Jun (2022). "Periodic Law of Chemistry Overturns for Superheavy Elements". ChemRxiv (preprint). doi:10.26434/chemrxiv-2022-l798p. Retrieved November 16, 2022. <a href="https://chemrxiv.org/engage/chemrxiv/article-details/63730be974b7b6d84cfdda35" target="_blank">https://chemrxiv.org/engage/chemrxiv/article-details/63730be974b7b6d84cfdda35</a> <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> <li id="fn:32"><p>Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae. <a href="https://www-nds.iaea.org/amdc/ame2020/NUBASE2020.pdf" target="_blank">https://www-nds.iaea.org/amdc/ame2020/NUBASE2020.pdf</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></p></li> <li id="fn:33"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:33" class="footnote-back-ref">↩</a></p></li> <li id="fn:34"><p>Considine, Glenn D., ed. (2005). Francium, in Van Nostrand's Encyclopedia of Chemistry. New York: Wiley-Interscience. p. 679. ISBN 978-0-471-61525-5. <a href="978-0-471-61525-5" target="_blank">978-0-471-61525-5</a> <a href="#fnref:34" class="footnote-back-ref">↩</a></p></li> <li id="fn:35"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:35" class="footnote-back-ref">↩</a></p></li> <li id="fn:36"><p>"Francium". McGraw-Hill Encyclopedia of Science & Technology. Vol. 7. McGraw-Hill Professional. 2002. pp. 493–494. ISBN 978-0-07-913665-7. <a href="978-0-07-913665-7" target="_blank">978-0-07-913665-7</a> <a href="#fnref:36" class="footnote-back-ref">↩</a></p></li> <li id="fn:37"><p>Considine, Glenn D., ed. (2005). Chemical Elements, in Van Nostrand's Encyclopedia of Chemistry. New York: Wiley-Interscience. p. 332. ISBN 978-0-471-61525-5. <a href="978-0-471-61525-5" target="_blank">978-0-471-61525-5</a> <a href="#fnref:37" class="footnote-back-ref">↩</a></p></li> <li id="fn:38"><p>National Nuclear Data Center (1990). "Table of Isotopes decay data". Brookhaven National Laboratory. Archived from the original on October 31, 2006. Retrieved April 4, 2007. <a href="https://web.archive.org/web/20061031212436/http://ie.lbl.gov/toi/nuclide.asp?iZA=870223" target="_blank">https://web.archive.org/web/20061031212436/http://ie.lbl.gov/toi/nuclide.asp?iZA=870223</a> <a href="#fnref:38" class="footnote-back-ref">↩</a></p></li> <li id="fn:39"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:39" class="footnote-back-ref">↩</a></p></li> <li id="fn:40"><p>Considine, Glenn D., ed. (2005). Chemical Elements, in Van Nostrand's Encyclopedia of Chemistry. New York: Wiley-Interscience. p. 332. ISBN 978-0-471-61525-5. <a href="978-0-471-61525-5" target="_blank">978-0-471-61525-5</a> <a href="#fnref:40" class="footnote-back-ref">↩</a></p></li> <li id="fn:41"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:41" class="footnote-back-ref">↩</a></p></li> <li id="fn:42"><p>Peppard, D. F.; Mason, G. W.; Gray, P. R.; Mech, J. F. (1952). "Occurrence of the (4n + 1) series in nature" (PDF). Journal of the American Chemical Society. 74 (23): 6081–6084. Bibcode:1952JAChS..74.6081P. doi:10.1021/ja01143a074. <a href="https://digital.library.unt.edu/ark:/67531/metadc172698/m2/1/high_res_d/metadc172698.pdf" target="_blank">https://digital.library.unt.edu/ark:/67531/metadc172698/m2/1/high_res_d/metadc172698.pdf</a> <a href="#fnref:42" class="footnote-back-ref">↩</a></p></li> <li id="fn:43"><p>Belli, P.; Bernabei, R.; Danevich, F. A.; et al. (2019). "Experimental searches for rare alpha and beta decays". European Physical Journal A. 55 (8): 140–1–140–7. arXiv:1908.11458. Bibcode:2019EPJA...55..140B. doi:10.1140/epja/i2019-12823-2. ISSN 1434-601X. S2CID 201664098. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:43" class="footnote-back-ref">↩</a></p></li> <li id="fn:44"><p>AME2020 gives 222Rn a lower mass than 222Fr,[27] which would forbid single beta decay, though it is possible within the given error margin and is explicitly predicted by Belli et al.[28] <a href="#fnref:44" class="footnote-back-ref">↩</a></p></li> <li id="fn:45"><p>Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae. <a href="https://www-nds.iaea.org/amdc/ame2020/NUBASE2020.pdf" target="_blank">https://www-nds.iaea.org/amdc/ame2020/NUBASE2020.pdf</a> <a href="#fnref:45" class="footnote-back-ref">↩</a></p></li> <li id="fn:46"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:46" class="footnote-back-ref">↩</a></p></li> <li id="fn:47"><p>Winter, Mark. "Uses". Francium. The University of Sheffield. Retrieved March 25, 2007. <a href="http://www.webelements.com/webelements/elements/text/Fr/uses.html" target="_blank">http://www.webelements.com/webelements/elements/text/Fr/uses.html</a> <a href="#fnref:47" class="footnote-back-ref">↩</a></p></li> <li id="fn:48"><p>Emsley, John (2001). Nature's Building Blocks. Oxford: Oxford University Press. pp. 151–153. ISBN 978-0-19-850341-5. <a href="978-0-19-850341-5" target="_blank">978-0-19-850341-5</a> <a href="#fnref:48" class="footnote-back-ref">↩</a></p></li> <li id="fn:49"><p>Gagnon, Steve. "Francium". Jefferson Science Associates, LLC. Retrieved April 1, 2007. <a href="http://education.jlab.org/itselemental/ele087.html" target="_blank">http://education.jlab.org/itselemental/ele087.html</a> <a href="#fnref:49" class="footnote-back-ref">↩</a></p></li> <li id="fn:50"><p>Considine, Glenn D., ed. (2005). Chemical Elements, in Van Nostrand's Encyclopedia of Chemistry. New York: Wiley-Interscience. p. 332. ISBN 978-0-471-61525-5. <a href="978-0-471-61525-5" target="_blank">978-0-471-61525-5</a> <a href="#fnref:50" class="footnote-back-ref">↩</a></p></li> <li id="fn:51"><p>Haverlock, T. J.; Mirzadeh, S.; Moyer, B. A. (2003). "Selectivity of calix[4]arene-bis(benzocrown-6) in the complexation and transport of francium ion". J Am Chem Soc. 125 (5): 1126–7. Bibcode:2003JAChS.125.1126H. doi:10.1021/ja0255251. PMID 12553788. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:51" class="footnote-back-ref">↩</a></p></li> <li id="fn:52"><p>Price, Andy (December 20, 2004). "Francium". Retrieved February 19, 2012. <a href="http://www.andyscouse.com/pages/francium.htm" target="_blank">http://www.andyscouse.com/pages/francium.htm</a> <a href="#fnref:52" class="footnote-back-ref">↩</a></p></li> <li id="fn:53"><p>Emsley, John (2001). Nature's Building Blocks. Oxford: Oxford University Press. pp. 151–153. ISBN 978-0-19-850341-5. <a href="978-0-19-850341-5" target="_blank">978-0-19-850341-5</a> <a href="#fnref:53" class="footnote-back-ref">↩</a></p></li> <li id="fn:54"><p>Gomez, E.; Orozco, L A; Sprouse, G D (November 7, 2005). "Spectroscopy with trapped francium: advances and perspectives for weak interaction studies". Rep. Prog. Phys. 69 (1): 79–118. Bibcode:2006RPPh...69...79G. doi:10.1088/0034-4885/69/1/R02. S2CID 15917603. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:54" class="footnote-back-ref">↩</a></p></li> <li id="fn:55"><p>Peterson, I. (May 11, 1996). "Creating, cooling, trapping francium atoms" (PDF). Science News. 149 (19): 294. doi:10.2307/3979560. JSTOR 3979560. Archived from the original (PDF) on July 27, 2020. Retrieved September 11, 2001. <a href="https://web.archive.org/web/20200727014700/https://www.sciencenews.org/pages/pdfs/data/1996/149-19/14919-06.pdf" target="_blank">https://web.archive.org/web/20200727014700/https://www.sciencenews.org/pages/pdfs/data/1996/149-19/14919-06.pdf</a> <a href="#fnref:55" class="footnote-back-ref">↩</a></p></li> <li id="fn:56"><p>Osika, Yuliya; Meniailava, Darya; Shundalau, Maksim (2024). "Relativistic coupled cluster study on the spectroscopic and radiative properties of the KFr molecule and modeling of the transport properties of potassium–francium dilute gas medium". Journal of Quantitative Spectroscopy and Radiative Transfer. 321. Elsevier BV: 108996. Bibcode:2024JQSRT.32108996O. doi:10.1016/j.jqsrt.2024.108996. ISSN 0022-4073. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:56" class="footnote-back-ref">↩</a></p></li> <li id="fn:57"><p>Price, Andy (December 20, 2004). "Francium". Retrieved February 19, 2012. <a href="http://www.andyscouse.com/pages/francium.htm" target="_blank">http://www.andyscouse.com/pages/francium.htm</a> <a href="#fnref:57" class="footnote-back-ref">↩</a></p></li> <li id="fn:58"><p>Adloff, Jean-Pierre; Kaufman, George B. (September 25, 2005). Francium (Atomic Number 87), the Last Discovered Natural Element Archived June 4, 2013, at the Wayback Machine . The Chemical Educator 10 (5). Retrieved on March 26, 2007. <a href="http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm" target="_blank">http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm</a> <a href="#fnref:58" class="footnote-back-ref">↩</a></p></li> <li id="fn:59"><p>Adloff, Jean-Pierre; Kaufman, George B. (September 25, 2005). Francium (Atomic Number 87), the Last Discovered Natural Element Archived June 4, 2013, at the Wayback Machine . The Chemical Educator 10 (5). Retrieved on March 26, 2007. <a href="http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm" target="_blank">http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm</a> <a href="#fnref:59" class="footnote-back-ref">↩</a></p></li> <li id="fn:60"><p>Fontani, Marco (September 10, 2005). "The Twilight of the Naturally-Occurring Elements: Moldavium (Ml), Sequanium (Sq) and Dor (Do)". International Conference on the History of Chemistry. Lisbon. pp. 1–8. Archived from the original on February 24, 2006. Retrieved April 8, 2007. <a href="/wiki/Marco_Fontani" target="_blank">/wiki/Marco_Fontani</a> <a href="#fnref:60" class="footnote-back-ref">↩</a></p></li> <li id="fn:61"><p>Van der Krogt, Peter (January 10, 2006). "Francium". Elementymology & Elements Multidict. Retrieved April 8, 2007. <a href="http://elements.vanderkrogt.net/element.php?sym=Fr" target="_blank">http://elements.vanderkrogt.net/element.php?sym=Fr</a> <a href="#fnref:61" class="footnote-back-ref">↩</a></p></li> <li id="fn:62"><p>Fontani, Marco (September 10, 2005). "The Twilight of the Naturally-Occurring Elements: Moldavium (Ml), Sequanium (Sq) and Dor (Do)". International Conference on the History of Chemistry. Lisbon. pp. 1–8. Archived from the original on February 24, 2006. Retrieved April 8, 2007. <a href="/wiki/Marco_Fontani" target="_blank">/wiki/Marco_Fontani</a> <a href="#fnref:62" class="footnote-back-ref">↩</a></p></li> <li id="fn:63"><p>Van der Krogt, Peter (January 10, 2006). "Francium". Elementymology & Elements Multidict. Retrieved April 8, 2007. <a href="http://elements.vanderkrogt.net/element.php?sym=Fr" target="_blank">http://elements.vanderkrogt.net/element.php?sym=Fr</a> <a href="#fnref:63" class="footnote-back-ref">↩</a></p></li> <li id="fn:64"><p>Fontani, Marco (September 10, 2005). "The Twilight of the Naturally-Occurring Elements: Moldavium (Ml), Sequanium (Sq) and Dor (Do)". International Conference on the History of Chemistry. Lisbon. pp. 1–8. Archived from the original on February 24, 2006. Retrieved April 8, 2007. <a href="/wiki/Marco_Fontani" target="_blank">/wiki/Marco_Fontani</a> <a href="#fnref:64" class="footnote-back-ref">↩</a></p></li> <li id="fn:65"><p>Van der Krogt, Peter (January 10, 2006). "Francium". Elementymology & Elements Multidict. Retrieved April 8, 2007. <a href="http://elements.vanderkrogt.net/element.php?sym=Fr" target="_blank">http://elements.vanderkrogt.net/element.php?sym=Fr</a> <a href="#fnref:65" class="footnote-back-ref">↩</a></p></li> <li id="fn:66"><p>"Alabamine & Virginium". Time. February 15, 1932. Archived from the original on September 30, 2007. Retrieved April 1, 2007. <a href="https://web.archive.org/web/20070930015028/http://www.time.com/time/magazine/article/0,9171,743159,00.html" target="_blank">https://web.archive.org/web/20070930015028/http://www.time.com/time/magazine/article/0,9171,743159,00.html</a> <a href="#fnref:66" class="footnote-back-ref">↩</a></p></li> <li id="fn:67"><p>MacPherson, H. G. (1934). "An Investigation of the Magneto-Optic Method of Chemical Analysis". Physical Review. 47 (4): 310–315. Bibcode:1935PhRv...47..310M. doi:10.1103/PhysRev.47.310. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:67" class="footnote-back-ref">↩</a></p></li> <li id="fn:68"><p>Fontani, Marco (September 10, 2005). "The Twilight of the Naturally-Occurring Elements: Moldavium (Ml), Sequanium (Sq) and Dor (Do)". International Conference on the History of Chemistry. Lisbon. pp. 1–8. Archived from the original on February 24, 2006. Retrieved April 8, 2007. <a href="/wiki/Marco_Fontani" target="_blank">/wiki/Marco_Fontani</a> <a href="#fnref:68" class="footnote-back-ref">↩</a></p></li> <li id="fn:69"><p>Van der Krogt, Peter (January 10, 2006). "Francium". Elementymology & Elements Multidict. Retrieved April 8, 2007. <a href="http://elements.vanderkrogt.net/element.php?sym=Fr" target="_blank">http://elements.vanderkrogt.net/element.php?sym=Fr</a> <a href="#fnref:69" class="footnote-back-ref">↩</a></p></li> <li id="fn:70"><p>Fontani, Marco (September 10, 2005). "The Twilight of the Naturally-Occurring Elements: Moldavium (Ml), Sequanium (Sq) and Dor (Do)". International Conference on the History of Chemistry. Lisbon. pp. 1–8. Archived from the original on February 24, 2006. Retrieved April 8, 2007. <a href="/wiki/Marco_Fontani" target="_blank">/wiki/Marco_Fontani</a> <a href="#fnref:70" class="footnote-back-ref">↩</a></p></li> <li id="fn:71"><p>Van der Krogt, Peter (January 10, 2006). "Francium". Elementymology & Elements Multidict. Retrieved April 8, 2007. <a href="http://elements.vanderkrogt.net/element.php?sym=Fr" target="_blank">http://elements.vanderkrogt.net/element.php?sym=Fr</a> <a href="#fnref:71" class="footnote-back-ref">↩</a></p></li> <li id="fn:72"><p>Adloff, Jean-Pierre; Kaufman, George B. (September 25, 2005). Francium (Atomic Number 87), the Last Discovered Natural Element Archived June 4, 2013, at the Wayback Machine . The Chemical Educator 10 (5). Retrieved on March 26, 2007. <a href="http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm" target="_blank">http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm</a> <a href="#fnref:72" class="footnote-back-ref">↩</a></p></li> <li id="fn:73"><p>Adloff, Jean-Pierre; Kaufman, George B. (September 25, 2005). Francium (Atomic Number 87), the Last Discovered Natural Element Archived June 4, 2013, at the Wayback Machine . The Chemical Educator 10 (5). Retrieved on March 26, 2007. <a href="http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm" target="_blank">http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm</a> <a href="#fnref:73" class="footnote-back-ref">↩</a></p></li> <li id="fn:74"><p>"Francium". McGraw-Hill Encyclopedia of Science & Technology. Vol. 7. McGraw-Hill Professional. 2002. pp. 493–494. ISBN 978-0-07-913665-7. <a href="978-0-07-913665-7" target="_blank">978-0-07-913665-7</a> <a href="#fnref:74" class="footnote-back-ref">↩</a></p></li> <li id="fn:75"><p>Adloff, Jean-Pierre; Kaufman, George B. (September 25, 2005). Francium (Atomic Number 87), the Last Discovered Natural Element Archived June 4, 2013, at the Wayback Machine . The Chemical Educator 10 (5). Retrieved on March 26, 2007. <a href="http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm" target="_blank">http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm</a> <a href="#fnref:75" class="footnote-back-ref">↩</a></p></li> <li id="fn:76"><p>Adloff, Jean-Pierre; Kaufman, George B. (September 25, 2005). Francium (Atomic Number 87), the Last Discovered Natural Element Archived June 4, 2013, at the Wayback Machine . The Chemical Educator 10 (5). Retrieved on March 26, 2007. <a href="http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm" target="_blank">http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm</a> <a href="#fnref:76" class="footnote-back-ref">↩</a></p></li> <li id="fn:77"><p>Price, Andy (December 20, 2004). "Francium". Retrieved February 19, 2012. <a href="http://www.andyscouse.com/pages/francium.htm" target="_blank">http://www.andyscouse.com/pages/francium.htm</a> <a href="#fnref:77" class="footnote-back-ref">↩</a></p></li> <li id="fn:78"><p>Grant, Julius (1969). "Francium". Hackh's Chemical Dictionary. McGraw-Hill. pp. 279–280. ISBN 978-0-07-024067-4. <a href="978-0-07-024067-4" target="_blank">978-0-07-024067-4</a> <a href="#fnref:78" class="footnote-back-ref">↩</a></p></li> <li id="fn:79"><p>Adloff, Jean-Pierre; Kaufman, George B. (September 25, 2005). Francium (Atomic Number 87), the Last Discovered Natural Element Archived June 4, 2013, at the Wayback Machine . The Chemical Educator 10 (5). Retrieved on March 26, 2007. <a href="http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm" target="_blank">http://chemeducator.org/sbibs/s0010005/spapers/1050387gk.htm</a> <a href="#fnref:79" class="footnote-back-ref">↩</a></p></li> <li id="fn:80"><p>"History". Francium. State University of New York at Stony Brook. February 20, 2007. Archived from the original on February 3, 1999. Retrieved March 26, 2007. <a href="https://archive.today/19990203121919/http://fr.physics.sunysb.edu/francium_news/history.HTM" target="_blank">https://archive.today/19990203121919/http://fr.physics.sunysb.edu/francium_news/history.HTM</a> <a href="#fnref:80" class="footnote-back-ref">↩</a></p></li> <li id="fn:81"><p>CRC Handbook of Chemistry and Physics. Vol. 4. CRC. 2006. p. 12. ISBN 978-0-8493-0474-3. <a href="978-0-8493-0474-3" target="_blank">978-0-8493-0474-3</a> <a href="#fnref:81" class="footnote-back-ref">↩</a></p></li> <li id="fn:82"><p>Emsley, John (2001). Nature's Building Blocks. Oxford: Oxford University Press. pp. 151–153. ISBN 978-0-19-850341-5. <a href="978-0-19-850341-5" target="_blank">978-0-19-850341-5</a> <a href="#fnref:82" class="footnote-back-ref">↩</a></p></li> <li id="fn:83"><p>Krebs, Robert E. (July 30, 2006). The History and Use of Our Earth's Chemical Elements: A Reference Guide. Bloomsbury Publishing USA. ISBN 978-0-313-02798-7. <a href="978-0-313-02798-7" target="_blank">978-0-313-02798-7</a> <a href="#fnref:83" class="footnote-back-ref">↩</a></p></li> <li id="fn:84"><p>"Production of Francium". Francium. State University of New York at Stony Brook. February 20, 2007. Archived from the original on October 12, 2007. Retrieved March 26, 2007. <a href="https://archive.today/20071012010344/http://fr.physics.sunysb.edu/francium_news/production.HTM" target="_blank">https://archive.today/20071012010344/http://fr.physics.sunysb.edu/francium_news/production.HTM</a> <a href="#fnref:84" class="footnote-back-ref">↩</a></p></li> <li id="fn:85"><p>"Cooling and Trapping". Francium. State University of New York at Stony Brook. February 20, 2007. Archived from the original on November 22, 2007. Retrieved May 1, 2007. <a href="https://archive.today/20071122170110/http://fr.physics.sunysb.edu/francium_news/trapping.HTM" target="_blank">https://archive.today/20071122170110/http://fr.physics.sunysb.edu/francium_news/trapping.HTM</a> <a href="#fnref:85" class="footnote-back-ref">↩</a></p></li> <li id="fn:86"><p>"Cooling and Trapping". Francium. State University of New York at Stony Brook. February 20, 2007. Archived from the original on November 22, 2007. Retrieved May 1, 2007. <a href="https://archive.today/20071122170110/http://fr.physics.sunysb.edu/francium_news/trapping.HTM" target="_blank">https://archive.today/20071122170110/http://fr.physics.sunysb.edu/francium_news/trapping.HTM</a> <a href="#fnref:86" class="footnote-back-ref">↩</a></p></li> <li id="fn:87"><p>Orozco, Luis A. (2003). "Francium". Chemical and Engineering News. 81 (36): 159. doi:10.1021/cen-v081n036.p159. <a href="http://pubs.acs.org/cen/80th/francium.html" target="_blank">http://pubs.acs.org/cen/80th/francium.html</a> <a href="#fnref:87" class="footnote-back-ref">↩</a></p></li> <li id="fn:88"><p>Orozco, Luis A. (September 30, 2014). Project Closeout Report: Francium Trapping Facility at TRIUMF (Report). U.S. Department of Energy. doi:10.2172/1214938. <a href="https://www.osti.gov/servlets/purl/1214938" target="_blank">https://www.osti.gov/servlets/purl/1214938</a> <a href="#fnref:88" class="footnote-back-ref">↩</a></p></li> <li id="fn:89"><p>Tandecki, M; Zhang, J.; Collister, R.; Aubin, S.; Behr, J. A.; Gomez, E.; Gwinner, G.; Orozco, L. A.; Pearson, M. R. (2013). "Commissioning of the Francium Trapping Facility at TRIUMF". Journal of Instrumentation. 8 (12): 12006. arXiv:1312.3562. Bibcode:2013JInst...8P2006T. doi:10.1088/1748-0221/8/12/P12006. S2CID 15501597. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:89" class="footnote-back-ref">↩</a></p></li> <li id="fn:90"><p>"Francium". McGraw-Hill Encyclopedia of Science & Technology. Vol. 7. McGraw-Hill Professional. 2002. pp. 493–494. ISBN 978-0-07-913665-7. <a href="978-0-07-913665-7" target="_blank">978-0-07-913665-7</a> <a href="#fnref:90" class="footnote-back-ref">↩</a></p></li> <li id="fn:91"><p>Keller, Cornelius; Wolf, Walter; Shani, Jashovam. "Radionuclides, 2. Radioactive Elements and Artificial Radionuclides". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.o22_o15. ISBN 978-3-527-30673-2. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:91" class="footnote-back-ref">↩</a></p></li> <li id="fn:92"><p>Orozco, Luis A. (2003). "Francium". Chemical and Engineering News. 81 (36): 159. doi:10.1021/cen-v081n036.p159. <a href="http://pubs.acs.org/cen/80th/francium.html" target="_blank">http://pubs.acs.org/cen/80th/francium.html</a> <a href="#fnref:92" class="footnote-back-ref">↩</a></p></li> <li id="fn:93"><p>Price, Andy (December 20, 2004). "Francium". Retrieved February 19, 2012. <a href="http://www.andyscouse.com/pages/francium.htm" target="_blank">http://www.andyscouse.com/pages/francium.htm</a> <a href="#fnref:93" class="footnote-back-ref">↩</a></p></li> <li id="fn:94"><p>Emsley, John (2001). Nature's Building Blocks. Oxford: Oxford University Press. pp. 151–153. ISBN 978-0-19-850341-5. <a href="978-0-19-850341-5" target="_blank">978-0-19-850341-5</a> <a href="#fnref:94" class="footnote-back-ref">↩</a></p></li> <li id="fn:95"><p>"Francium". Los Alamos National Laboratory. 2011. Retrieved February 19, 2012. <a href="http://periodic.lanl.gov/87.shtml" target="_blank">http://periodic.lanl.gov/87.shtml</a> <a href="#fnref:95" class="footnote-back-ref">↩</a></p></li> </ol>