Periodic Trends
Beryllium Boron Carbon Nitrogen Oxygen Fluorine NeonPeriod 2 is the first period in the periodic table that periodic trends can be drawn from. Period 1, which only contains two elements (hydrogen and helium) is too small to draw any conclusive trends from it, especially since the two elements behave nothing like other s-block elements. Period 2 has much more conclusive trends. For all elements in period 2, as the atomic number increases, the atomic radius of the elements decreases, the electronegativity increases, and the ionization energy increases.
Period 2 only has two metals (lithium and beryllium), making it the least metallic period (period 1 has no metals, but as mentioned above, only has two elements, so it would be impossible to have more metals) and the most nonmetals, with four. The elements in period 2 often have the most extreme properties in their respective groups; for example, fluorine is the most reactive halogen, neon is the most inert noble gas, and lithium is the least reactive alkali metal.
All period 2 elements completely obey the Madelung rule; in period 2s, lithium and beryllium fill the 2s subshell, and boron, carbon, nitrogen, oxygen, fluorine, and neon fill the 2p subshell. It period shares this trait with periods 1 and 3, none of which contain transition elements or inner transition elements, which often vary from the rule.
Read more about this topic: Period 2 Element
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