Which pair below describes isotopes of the same element?

B) an atom with 6 protons and 6 neutrons - an atom with 6 protons and 7 neutrons

Explanation:An atom is the smallest particle of an element that can take part in a chemical reaction.Atoms consists of subatomic particles neutrons, electrons and protons.Atoms of the same element have an equal number of protons in their nucleus.Atoms may, however, differ in the number of neutrons. Such atoms that have a different number of neutrons but an equal number of protons are known as isotopes of an element.

They can measure  the amount of energy gained or lost