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Lanthanide contraction
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<p>The lanthanide contraction is the greater-than-expected decrease in <a href="/facts/Atomic_radius/0mQaIJX9">atomic radii</a> and <a href="/facts/Ionic_radius/C3dwKrrB">ionic radii</a> of the <a href="/facts/Chemical_element/0jducgWD">elements</a> in the <a href="/facts/Lanthanide/rt3XIRCl">lanthanide</a> series, from left to right. It is caused by the poor <a href="/facts/Shielding_effect/PoyU5vNr">shielding</a> effect of nuclear charge by the <a href="/facts/F_subshell/QxI30eh9">4f</a> <a href="/facts/Electron/L0KBo5cW">electrons</a> along with the expected <a href="/facts/Periodic_trends/dI0mkSju">periodic trend</a> of increasing <a href="/facts/Electronegativity/H7Vq7Uah">electronegativity</a> and <a href="/facts/Atomic_number/bgAr581S">nuclear charge</a> on moving from left to right. About 10% of the lanthanide contraction has been attributed to <a href="/facts/Relativistic_effect/8A1se1CS">relativistic effects</a>. </p><p>A decrease in atomic radii can be observed across the 4f elements from <a href="/facts/Atomic_number/bgAr581S">atomic number</a> 57, <a href="/facts/Lanthanum/Uhmmy1sB">lanthanum</a>, to 70, <a href="/facts/Ytterbium/3lerM9uf">ytterbium</a>. This results in smaller than otherwise expected atomic radii and ionic radii for the subsequent d-block elements starting with 71, <a href="/facts/Lutetium/URlmnYG8">lutetium</a>. This effect causes the radii of <a href="/facts/Transition_metal/0slGWoLQ">transition metals</a> of group 5 and 6 to become unusually similar, as the expected increase in radius going down a period is nearly cancelled out by the f-block insertion, and has many other far ranging consequences in post-lanthanide elements. </p><p>The decrease in ionic radii (Ln3+) is much more uniform compared to decrease in atomic radii. </p> <table><tbody><tr><th>Element</th><th>Atomic electron configuration(all begin with [Xe])</th><th>Ln3+ electron configuration</th><th>Ln3+ radius (pm) (6-coordinate)</th></tr><tr><td><a href="/facts/Lanthanum/Uhmmy1sB">La</a></td><td>5d16s2</td><td>4f0</td><td>103</td></tr><tr><td><a href="/facts/Cerium/a7UjMBQ6">Ce</a></td><td>4f15d16s2</td><td>4f1</td><td>102</td></tr><tr><td><a href="/facts/Praseodymium/2lnRJ9dH">Pr</a></td><td>4f36s2</td><td>4f2</td><td>99</td></tr><tr><td><a href="/facts/Neodymium/GzDkTIoI">Nd</a></td><td>4f46s2</td><td>4f3</td><td>98.3</td></tr><tr><td><a href="/facts/Promethium/8xvCz9Rg">Pm</a></td><td>4f56s2</td><td>4f4</td><td>97</td></tr><tr><td><a href="/facts/Samarium/09K3kl93">Sm</a></td><td>4f66s2</td><td>4f5</td><td>95.8</td></tr><tr><td><a href="/facts/Europium/dqmBm1vr">Eu</a></td><td>4f76s2</td><td>4f6</td><td>94.7</td></tr><tr><td><a href="/facts/Gadolinium/eLYUeScu">Gd</a></td><td>4f75d16s2</td><td>4f7</td><td>93.8</td></tr><tr><td><a href="/facts/Terbium/ICF3PMED">Tb</a></td><td>4f96s2</td><td>4f8</td><td>92.3</td></tr><tr><td><a href="/facts/Dysprosium/eMev6zGS">Dy</a></td><td>4f106s2</td><td>4f9</td><td>91.2</td></tr><tr><td><a href="/facts/Holmium/C73kJVtp">Ho</a></td><td>4f116s2</td><td>4f10</td><td>90.1</td></tr><tr><td><a href="/facts/Erbium/XEJlgJcx">Er</a></td><td>4f126s2</td><td>4f11</td><td>89</td></tr><tr><td><a href="/facts/Thulium/G2905xhd">Tm</a></td><td>4f136s2</td><td>4f12</td><td>88</td></tr><tr><td><a href="/facts/Ytterbium/3lerM9uf">Yb</a></td><td>4f146s2</td><td>4f13</td><td>86.8</td></tr><tr><td><a href="/facts/Lutetium/URlmnYG8">Lu</a></td><td>4f145d16s2</td><td>4f14</td><td>86.1</td></tr></tbody></table> <p>The term was coined by the Norwegian geochemist <a href="/facts/Victor_Goldschmidt/50GFw2Pl">Victor Goldschmidt</a> in his series "Geochemische Verteilungsgesetze der Elemente" (Geochemical distribution laws of the elements). </p>