Question

Do elements that have many similar properties belong to the same period or group on the periodic table?

Answer 1

They belong to the same `"Group"`, the same vertical column on the Periodic Table.

Explanation:

The modern Periodic Table graphically describes the electronic structure of the elements. To a first approximation, elements that are members of the same Group have the same number of valence electrons, and thus display similar properties, and similar chemistry.

While there are of course significant differences, the chemistry of `Li` is similar to that of the lower alkali metals, the chemistry of the alkaline earth metals forms a category, and across the Table to the non-metals. each Group represents a distinct valence electron configuration, and a distinct chemistry.