Question

valence is the number of electrons an atom must gain or lose in order to _____ its outer shell or have a stable octet in its outer shell.

Answer 1

complete

Step-by-step explanation:

an valence can't be completed unless the outer shell is closed and stable

Answer 2

Valence is the number of electrons an atom must gain or lose in order to complete its outer shell or have a stable octet in its outer shell.