Answer:
valence electrons an element has in its outer shell, the easier it is to complete.
The most electron shells an element has, the easier it is to fill its outermost shell.
Explanation:
Non metals atoms bond to other elements by sharing or completing the valance electrons in other element. This is easily made when the other element lacks a small number of electrons, for example with Hydrogen it has 1 valance electron because of that it is easier to bond with other elements.
