Solution
Sodium has 1 valence electron.
Explanation:
Your tool of choice here will be the Periodic Table of Elements. Grab one and look for sodium, Na. You’ll find it located in period 3, group 1.
The thing to remember about main-group elements, which are those elements located in groups 1, 2, and 13 18, is that their group number tells you the number of valence electrons.
In your case, sodium is located in the group 1, which means that it has 1 valence electron. This valence electron is located in sodium’s third energy shell.