Question

1. how do you determine the number of valance electrons that an element has?

Explanation:

For main - group elements (groups 1 - 2 and 13 - 18), the number of valence electrons is equal to the group number (with group 13 having 3, group 14 having 4, etc.). For transition metals, the number of valence electrons is more complex and usually involves the outermost s - electrons and some d - electrons.

Answer:

For main - group elements, use the group number. For transition metals, it's more complex involving s and some d electrons.