If we look at the atomic number, mass number and neutrons of different atoms, we can find sets of atoms with another equal number.
Isotopes are atoms that have the same number of protons (p) and different mass number (A). Example: hydrogen (H).
¹H ²H ³H
¹ ¹ ¹
hydrogen deuterium tritium
Z = 1 Z = 1 Z = 1
A = 1 A = 2 A = 3
This phenomenon is very common in nature. Almost all natural chemical elements are formed by mixing isotopes.
Isobars are atoms that have the same mass number (A) and different number of protons. Example:
A = 40
A = 40
They are atoms of different chemical elements, but they have the same mass number.
Isotons are atoms that have the same number of neutrons and with different numbers of protons and mass. They are atoms of different chemical elements. Example:
A = 37Cl
A = 40Here
Isotones have different chemical and physical properties.