How does an atom's valence electrons influence the element's chemical properties ?
The valence electrons are the electrons found in the highest occupied energy level of an atom. Going down the rows of the Periodic Table are groupings of "families" of elements. Even though they are different atoms, and they tend to increase in size, they all share similar chemical properties in a given column, because their electron configurations are similar at the outer part of the atom. For example, the first column of the Table are the alkali metal family; each of these elements has only one electron in its outermost orbit. See more details at the link: