An antiparticle is like a mirror‑image version of a particle. It has the same mass but the opposite electric charge. Think of it as a twin that looks identical but carries the opposite “handedness” of charge.
The electron is written as \$e^-\$ and carries a charge of –\$e\$. Its antiparticle, the positron, is written as \$e^+\$ and carries a charge of +\$e\$. Both have the same mass \$m_e\$:
\$m{e^-} = m{e^+} = 9.11 \times 10^{-31}\,\text{kg}.\$
Imagine a person standing in front of a mirror. The person and the reflection have the same height and weight (mass), but the reflection’s left and right are swapped (charge sign). That’s what happens between a particle and its antiparticle.
| Particle | Antiparticle | Charge |
|---|---|---|
| \$e^-\$ (electron) | \$e^+\$ (positron) | –\$e\$ / +\$e\$ |
| \$p^+\$ (proton) | \$\bar{p}^-\$ (antiproton) | +\$e\$ / –\$e\$ |
| \$n^0\$ (neutron) | \$\bar{n}^0\$ (antineutron) | 0 / 0 |
Remember: When asked to identify an antiparticle, check the charge sign and mass. For example, the antiparticle of \$e^-\$ is \$e^+\$, not \$e^-\$. Also, be careful with symbols: \$p^+\$ vs \$\bar{p}^-\$.
When an electron (\$e^-\$) meets a positron (\$e^+\$), they annihilate:
\$e^- + e^+ \rightarrow \gamma + \gamma,\$
producing two gamma‑ray photons. The energy released is \$2m_e c^2\$.
Antiparticles show that the universe is full of symmetry. Just as every particle has a counterpart, every action has an equal and opposite reaction. Keep this mirror‑image idea in mind, and you’ll ace questions about antiparticles and radiation in your exams!