What are alpha particles primarily composed of?

Alpha particles are primarily composed of helium nuclei, which consist of two protons and two neutrons. This composition gives alpha particles their specific characteristics, including a relatively high mass and a +2 charge due to the two positively charged protons.

The fact that an alpha particle is essentially a helium nucleus is significant in the context of nuclear reactions and radiation. When a radioactive element undergoes alpha decay, it emits an alpha particle, thereby losing two protons and two neutrons, which results in the formation of a new element that is two atomic numbers lower than the original. This process is a key concept in understanding radioactivity and the behavior of elements over time.

Understanding that alpha particles are helium nuclei also clarifies why they have limited penetration abilities. They can be stopped by a sheet of paper or the outer layer of human skin, which is a crucial aspect of safety and health standards in radiation exposure.

In contrast, the other options do not accurately describe the composition of alpha particles, as electrons are negatively charged subatomic particles, neutrons are neutral particles found in atomic nuclei, and carbon isotopes relate to different elements entirely, none of which share the same properties as alpha particles.