What is a particle identical to a helium nucleus, consisting of two protons and two neutrons?

A particle that is identical to a helium nucleus, which consists of two protons and two neutrons, is known as an alpha particle. In nuclear reactions, alpha particles are commonly emitted from heavy radioactive nuclei during alpha decay. This emission occurs because the nucleus wants to reach a more stable state, and by releasing an alpha particle, it decreases its atomic number by two and its mass number by four, effectively transforming into a new element.

The alpha particle's makeup, being comprised of two protons and two neutrons, directly aligns with the structure of the helium-4 nucleus, the most common isotope of helium. This identity is significant in understanding the processes of nuclear decay and the nature of different types of radiation.