Periodic trends

<p>In <a href="/facts/Chemistry/SrNqkGVm">chemistry</a>, periodic trends are specific patterns present in the <a href="/facts/Periodic_table/umdGIfUb">periodic table</a> that illustrate different aspects of certain <a href="/facts/Chemical_element/0jducgWD">elements</a> when grouped by <a href="/facts/Period_(periodic_table)/WpGUFh5V">period</a> and/or <a href="/facts/Group_(periodic_table)/YGBcUabv">group</a>. They were discovered by the Russian chemist <a href="/facts/Dmitri_Mendeleev/xdouRrx8">Dmitri Mendeleev</a> in 1863. Major periodic trends include <a href="/facts/Atomic_radius/0mQaIJX9">atomic radius</a>, <a href="/facts/Ionization_energy/lezUajfA">ionization energy</a>, <a href="/facts/Electron_affinity/1mf4A396">electron affinity</a>, <a href="/facts/Electronegativity/H7Vq7Uah">electronegativity</a>, <a href="/facts/Nucleophilicity/xYccoaJQ">nucleophilicity</a>, <a href="/facts/Electrophilicity/1AHFg1zm">electrophilicity</a>, <a href="/facts/Valence_(chemistry)/ck7cHByj">valency</a>, <a href="/facts/Nuclear_charge/FFpQ0ubY">nuclear charge</a>, and <a href="/facts/Metal/PT8hNX6R">metallic character</a>. <a href="/facts/Dmitri_Mendeleev/xdouRrx8">Mendeleev</a> built the foundation of the periodic table. Mendeleev organized the elements based on atomic weight, leaving empty spaces where he believed undiscovered elements would take their places. Mendeleev's discovery of this trend allowed him to predict the existence and properties of three unknown elements, which were later discovered by other chemists and named <a href="/facts/Gallium/EucevDs9">gallium</a>, <a href="/facts/Scandium/TJRt1chg">scandium</a>, and <a href="/facts/Germanium/wtoALHGs">germanium</a>. English physicist <a href="/facts/Henry_Moseley/W6Kd359o">Henry Moseley</a> discovered that organizing the elements by atomic number instead of atomic weight would naturally group elements with similar properties.
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Periodic trends open-in-new

Periodic trends