Atomic and Nuclear Nomenclature

An atom consists of a nucleus and electron system.
A nucleus is a many-bodied system consisting of protons and neutrons, collectively known as nucleons.

The diameter of an atom is of the order of 10-10 m.
The diameter of a nucleus is of the order of 10-15 m.

The number of neutrons in a nucleus is denoted by N.
The number of protons in a nucleus is denoted by Z, also known as the atomic number.
The mass number A is the sum of N+Z.

Isotopes have the same number of protons, Z, e.g. 235U, 236U, 238U

Isotones have the same number of neutrons, N, e.g. 12B and 13C

 Isobars have the same mass number, A, e.g. 40Ar, 40K, 40Ca, 40S, 40Cl,