Isotopes and Isomers

Isotopes
Isotopes are atoms of the same element with different numbers of neutrons. As they contain same number of protons or electrons, so chemically they are identical. But, as they have different number of neutrons, so they have different masses.

For example, Deuterium is isotopes of Hydrogen. Both have same atomic number (1). But different mass number: Hydrogen = 1; Deuterium = 2

Isomers
Molecules with identical molecular formulae but with different structural formulae are called Isomers.

For example, Butane and Isobutane are isomers because they have same molecular formulae, but different structure. As they have different structures, so they have different physical properties. And, as they have identical molecular formulae, so they react in a similar way.

DIFFERENCE BETWEEN
— Reversible and Irreversible Reaction
— Endothermic and Exothermic Reaction