What type of radioactive particle is described by a helium nucleus? Select the single best answer.

The type of radioactive particle described by a helium nucleus is an alpha particle.

An alpha particle consists of two protons and two neutrons, making it identical to the nucleus of a helium-4 atom. Alpha particles are emitted during the process of alpha decay, which is a type of radioactive decay. Because of their relatively large mass and positive charge, alpha particles have a low penetration ability; they can be stopped by a sheet of paper or even the outer layer of human skin. However, if alpha emitters are ingested or inhaled, they can pose significant health risks due to their high ionizing power.