Question

argon (ar) has atomic number = 18 and average atomic mass = 39.9
how many electrons does it have?
1
18
16
rewatch

Explanation:

In a neutral atom, the number of electrons equals the atomic number, as the positive charge of protons (equal to atomic number) balances the negative charge of electrons. Argon is a neutral atom with an atomic number of 18.

Answer:

18