Antimatter

Definition

Antimatter consists of particles that are the counterparts to the particles of ordinary matter, having the same mass but opposite charge. When antimatter and matter collide, they annihilate each other, releasing energy.

5 Must Know Facts For Your Next Test

1. An electron's antimatter counterpart is called a positron, which has the same mass as an electron but a positive charge.
2. Antimatter annihilation with matter produces high-energy photons, often in the form of gamma rays.
3. Positrons can be produced in certain types of radioactive decay, such as beta-plus decay.
4. In nuclear equations, antimatter particles are denoted with a bar over their symbol or by adding a plus sign for positrons (e.g., $\overline{p}$ for antiproton).
5. The discovery of antimatter was predicted by Paul Dirac's equation in 1928 and experimentally confirmed by Carl Anderson in 1932.

Review Questions

• What happens when a particle of matter collides with its corresponding antiparticle?
• Describe how positrons are represented in nuclear equations.
• Who predicted the existence of antimatter and who confirmed it experimentally?

Related terms

Positron: The antimatter counterpart to the electron; it has the same mass as an electron but carries a positive charge.

Beta-plus Decay: A type of radioactive decay where a proton is converted into a neutron, emitting a positron and a neutrino.

Gamma Rays: High-frequency electromagnetic waves often produced during annihilation events between matter and antimatter.