Alpha Particle
Definition and meaning of Alpha Particle in chemistry.
An alpha particle is a positively charged subatomic particle consisting of two protons and two neutrons, the nucleus of a helium-4 atom. Alpha particles are emitted when certain unstable atomic nuclei undergo radioactive decay.
In more detail
Alpha particles are produced through alpha decay, a radioactive process in which an unstable nucleus ejects a helium nucleus to achieve greater stability. Because alpha particles are relatively massive and carry a double positive charge, they have limited penetrating power and interact strongly with matter. While alpha particles can be stopped by paper, clothing, or skin, making them less hazardous than other radiation types at a distance, they pose severe health risks if inhaled or ingested. Inside the body, alpha particles cause significant ionization damage to surrounding tissues, making them particularly dangerous as internal contaminants.
Key facts
| Field | Physical Chemistry |
|---|---|
| Nuclear symbol | ⁴He or ⁴2He |
| Charge | +2 (doubly positive) |
| Composition | 2 protons + 2 neutrons |
When uranium-238 undergoes alpha decay, it transforms into thorium-234 while emitting an alpha particle, reducing the atomic number by 2 and the mass number by 4.
Frequently asked questions
Why is it called an alpha particle?
Historically, scientists designated three types of radiation emitted by radioactive materials using Greek letters, alpha, beta, and gamma. Alpha particles, being the least penetrating, were named first in this classification scheme.
What can stop alpha particles?
Alpha particles can be blocked by paper, aluminum foil, or even the dead outer layer of human skin, making them the least dangerous form of radiation from external sources.