Antimatter is much like normal matter, but its constituent particles carry the opposite electrical charge of their normal matter counterparts. Antiparticles can be created from energy in a particle accelerator, and they can form naturally during certain kinds of radioactive decay.
- The anti-particle for the electron is the positron. It has the same mass as an electron, but it carries a positive charge instead of a negative charge.
- The anti-particle for the proton is the antiproton. It has the same mass as a proton and a negative charge.
- The anti-particle for the neutron is the antineutron. It has the same mass as a neutron and carries no charge, but it will still annihilate a neutron because the antineutron itself is composed of charged antiquarks.
- Smaller subatomic particles like quarks also have antiparticles.
- Massless particles like photons generally don't have antiparticles.
If a particle of matter comes into contact with its anti-particle, both will "annihilate" each other, converting their combined mass into energy.
Antiparticles can chemically interact with each other in much the way ordinary particles do. For instance, an antiproton and a positron can combine to form anti-hydrogen.