Atomic Number, Mass Number, Isotope

Atomic Number, Mass Number, and Isotopes

The atomic number of an atom is the number of protons in its nucleus.
It is represented by the symbol ‘Z’.
It identifies the element type of the atom since each element has a unique atomic number.

The mass number (also known as the atomic mass) of an atom is the total number of protons and neutrons in its nucleus.
It is symbolised by ‘A’.
Protons and neutrons make up the majority of an atom’s mass, hence it’s also called atomic mass.

Isotopes are atoms of the same element (i.e., having the same atomic number) but different mass numbers (i.e., different number of neutrons).
For example, carbon-12 and carbon-14 are isotopes of carbon.
While the number of protons for isotopes of an element remains constant, the number of neutrons varies.
Physical properties of isotopes such as their rate of diffusion may vary, but their chemical properties remain the same as they have the same electron configuration.