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 \(_{M}^{A}X\)
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