Final answer:
The number of valence electrons an element has can be determined by its position in the periodic table group.
Step-by-step explanation:
The number of valence electrons of an element can be determined by the periodic table group (vertical column) in which the element is categorized. With the exception of groups 3-12 (the transition metals), the units digit of the group number identifies how many valence electrons are associated with a neutral atom of an element listed under that particular column. For example, Group 1 (alkali metals) has 1 valence electron, Group 14 (carbon group) has 4 valence electrons, and Group 17 (halogens) has 7 valence electrons.