Answer:

The number of protons in the nucleus of the atom is equal to the atomic number (Z). The number of electrons in a neutral atom is equal to the number of protons. The mass number of the atom (M) is equal to the sum of the number of protons and neutrons in the nucleus.

Answer:

Atomic no. of Argon = no. of protons = 18

No. of electrons =no. of protons = 18

Mass no. of Argon = no. of protons and neutrons = 40

so.,, no. of neutrons = 40 - 18 = 22