What part of an atom has a negative charge?
Quick answer
The electron is the part of an atom that carries a negative electric charge. Electrons move around the atom’s nucleus, which contains positively charged protons and neutral neutrons. In a neutral atom, the number of electrons equals the number of protons, so the charges balance.
The three main particles
| Particle | Charge | Where it is | Relative mass |
|---|---|---|---|
| Proton | +1 (positive) | Nucleus | 1 |
| Neutron | 0 (neutral) | Nucleus | About 1 |
| Electron | −1 (negative) | Around the nucleus | About 1/1,836 of a proton |
Because electrons are so light, almost all of an atom’s mass is in its tiny nucleus.
Who discovered the electron?
British physicist J. J. Thomson discovered the electron in 1897, while studying rays in glass tubes. It was the first subatomic particle ever found, proving that atoms are made of smaller pieces. Later, Ernest Rutherford discovered the nucleus (1911), and James Chadwick found the neutron (1932).
Why electrons matter
- Electricity is the flow of electrons through a material like copper wire.
- Chemical bonds form when atoms share or transfer electrons.
- Static electricity happens when electrons rub off one material onto another, such as a balloon on hair.
- Ions are atoms that have gained electrons (negative ions) or lost them (positive ions).
Where are electrons, exactly?
Old diagrams show electrons circling the nucleus like planets. Modern physics says electrons exist in fuzzy regions called orbitals, where they’re likely to be found, rather than fixed paths.
Electron flow is measured against resistance in ohms; see the SI unit of electrical resistance. For atoms in your body, read what amino acids are.
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