Any element can be represented with its atomic number, symbol and its atomic mass using a simple representation. Any element ‘X’ having the atomic number ‘A’ and atomic mass ‘M’ can be represented as _Μ^AX.

For ₁₆⁸O:

No. of protons = 8

No. of electrons = 8

No. of neutrons = (16 – 8) = 8 (atomic mass minus the protons is neutrons)

Atomic no. = 8

Mass no. = 16

For ₁₈⁴⁰Ar:

No. of protons = 18

No. of electrons = 18

No. of neutrons = (40 – 18) = 22

Atomic no. = 18

Mass no. = 40