What is the average atomic mass of element X: X- 10 98%
X - 11 1.5%
X - 12 0.5%
The answers to pick from are 10.025 amu or 11 amu or 10,565 amu or 12.05 amu.

The atom fluorine generally will become stable through the formation of an ionic chemical compound by accepting electron(s) from another atom. this process will fill its outer energy level of electrons.