What do the columns of the Periodic Table tell us?

The columns of the table represent groups, or families, of elements. The elements in a group often look and behave similarly, because they have the same number of electrons in their outermost shell,  the face they show to the world.

Explanation:

The columns tell you how many electrons are on the outest most shell of the atom.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.