Alpha particle

Alpha particles, also called alpha rays or alpha radiation, are tiny bits of matter. They are made of two protons and two neutrons bound together. They look like the nucleus of a helium-4 atom. They are named after the first letter of the Greek alphabet, which is α.

These particles are usually created when some radioactive materials go through a process called alpha decay. Because they are the same as helium nuclei, we can also write them as He²⁺ or ⁴₂He²⁺. This means a helium ion that is missing its two electrons. Once they pick up electrons, they become normal helium atoms ⁴₂He.

Alpha particles are good at pushing other atoms apart. But they do not go very far through things. Usually, just a few centimeters of air or the outer layer of skin can stop them. Some special alpha particles called long-range alpha particles can go farther. Also, some alpha particles from cosmic rays can go through the human body and even many meters of solid material.

Name

The name "alpha particle" was created by Ernest Rutherford when he studied radiation from uranium. He found two types of radiation: one he called "α radiation" and a more powerful type called "β radiation." Later, Hans Geiger and Rutherford discovered that alpha particles, after losing their charge, become helium atoms. Alpha radiation is made of particles that look like helium atoms without electrons. This is how we get helium gas on Earth.