Which of the following always changes when transmutation occurs?

The number of electrons

The mass number

The atomic number

The number of neutrons

The atomic number

Explanation:

Transmutation refers to the conversion of one chemical element into another. A transmutation usually involves a change in the structure of atomic nuclei and this may be induced by a nuclear reaction.

Transmutation was first achieved in 1919 by Lord Rutherford when he successfully changed a nitrogen nucleus to an oxygen-18 isotope, producing a proton in the process.

Since transmutation often involves changing one atom into another, the atomic number or mass number of the original element always changes (to form a new element) in the process.