Use the periodic table to determine the number of valence electrons in each of the following elements. Na:
E:
V:
Ar:

Na= 1, Ar= 8, V= 5, F= 7

Explanation:
You can determine the number of valence electrons in an element by looking the the group/column # on the periodic table. Elements in the same family/ group are organized by columns (vertical). Elements in the same column have the same number of valence electrons (electrons of the outermost shell) and consequently similar properties.
Simply put, GROUP #= # VALENCE E-

There are exceptions to this, especially when determining the amount of valence electrons in elements that are in a compound or in transition metal elements. For transition metals (that have different oxidation states- different # of valence electrons for the same element) I’d just look it up