Answer:
[tex]\huge\boxed{\sf 3 \ electrons}[/tex]
Explanation:
[tex]1s^22s^22p^1[/tex]
The outermost/valence shell is the second one, seeing from the electronic configuration.
= 2 + 1 = 3 (electrons are raised to the power in the electronic configuration)
Since, the valence shell here is 2, the electrons of second shell will be counted as valence electrons.
[tex]\rule[225]{225}{2}[/tex]