Why would an unstable radioactive isotope (nuclide) emit a beta particle (high energy electron) ?

A) It has too many neutrons

B) It has too many protons

C) It has too many electrons

D) It has too few electrons

A) It has too many neutrons

Explanation:

Electrons are emitted from the nucleus when a neutron is converted to a proton, an electron and a neutrino. This process is popularly known as beta emission. It reduces the neutron-proton ratio of a nuclide. The neutrino is a particle of zero mass and zero charge that carries off the excess energy and balances spins.

The loss of an electron from the nucleus occurs when there are too many neutrons in the nucleus. The process of beta emission usually reduces the number of neutrons in an atom thereby decreasing the neutron-proton ratio.