Period (periodic table) - Wikipedia
https://en.wikipedia.org/wiki/Period_(periodic_table)
A period in the periodic table is a row of chemical elements.All elements in a row have the same number of electron shells.Each next element in a period has one more proton and is less metallic than its predecessor. Arranged this way, groups of elements in the same column have similar chemical and physical properties, reflecting the periodic law.For example, the halogens lie in the second-last ...
DA: 66 PA: 87 MOZ Rank: 71