Which Subatomic Particle Has a Negative Charge? The Electron Explained
The electron is the subatomic particle with a negative electric charge. Its charge is exactly −1.602176634 × 10⁻¹⁹ coulombs, the negative of the elementary charge NIST CODATA. In an atom, electrons are found around the nucleus, which contains positively charged protons and, in most atoms, electrically neutral neutrons.
The minus sign describes how the electron responds to electric forces. Opposite charges attract, while charges with the same sign repel. So an electron is attracted to a proton and repelled by another electron. The sign is a convention, but the measured behavior is physical: an electron moves in response to electric fields in the direction associated with negative charge.
The charges of the particles in an atom
The three familiar particles in an atom have different electric charges:
| Particle | Electric charge | Where it is found |
|---|---|---|
| Electron | Negative, −1 elementary charge | Around the nucleus |
| Proton | Positive, +1 elementary charge | In the nucleus |
| Neutron | Zero | In the nucleus |
A neutral atom has the same number of protons and electrons. Their equal and opposite charges cancel, leaving the atom with no overall electric charge. If an atom gains or loses electrons, it becomes an ion with a net charge.
Electrons and protons have equal-sized charges with opposite signs. The charge of a neutron is zero. These labels describe electric charge, not the particle’s mass or location: an electron is negatively charged whether it is part of an atom or moving freely.
What is distinctive about an electron?
An electron is an elementary particle, classified as a lepton in the Standard Model of particle physics. It has no known smaller constituents. Protons and neutrons, by contrast, are composite particles made of quarks held together by the strong interaction. The distinction is useful, but it does not mean that scientists have a complete explanation for why the electron has its particular properties. Its charge is measured and used in physical theories; the reason it has that value is a deeper question.
The electron belongs to a group of six leptons: the electron, muon, tau, and three neutrinos CERN — The Standard Model. The electron, muon, and tau carry negative electric charge. Neutrinos have no electric charge. For each lepton, there is also an antiparticle. The electron’s antiparticle is the positron, which has the same mass as the electron but a positive charge.
The electron’s charge is described in units of the elementary charge. An electron carries one negative elementary charge; a proton carries one positive elementary charge. In ordinary atoms, the total charge depends on the balance between their numbers. The coulomb is a larger unit used to describe electric charge on a scale that is practical for measurements and applications.
How scientists identified the electron
In 1897, J. J. Thomson studied cathode rays and found evidence that they consisted of negatively charged particles much smaller in mass than atoms. The rays bent in an electric field toward a positively charged plate. That deflection showed that they carried negative charge Encyclopaedia Britannica — Electron.
The same basic principle makes the sign of a particle’s charge measurable. A charged particle in an electric field experiences a force. A negative particle is pulled toward the positive side of the field; a positive particle is pulled toward the negative side. A neutral particle has no electric force from the field, though other forces can still affect its motion.
The words “positive” and “negative” are conventions. Benjamin Franklin’s naming choice came before the electron was known. If the labels had originally been reversed, electrons might have been called positive and protons negative. The measured forces would be unchanged, as long as the convention were used consistently.
One example: a neutral helium-4 atom
A helium-4 atom contains two protons and two neutrons in its nucleus, with two electrons around the nucleus. The two protons contribute a total charge of +2 elementary charges, and the two electrons contribute −2. The neutron charges are zero, so the atom has no net electric charge.
This example also shows why the electron’s negative charge matters in atomic structure. The electrons are attracted to the positively charged nucleus. Their behavior is described by quantum mechanics, not by treating them as tiny planets traveling along fixed paths. The attraction between electrons and nuclei helps determine how atoms interact and form chemical bonds.
The electrons in a neutral atom do not make its parts electrically neutral individually. The nucleus is positively charged, and the surrounding electrons carry an equal total negative charge. The atom as a whole is neutral because those charges balance. If the atom loses an electron, it has more positive charge than negative charge and becomes a positive ion. If it gains an electron, it becomes a negative ion.
Key Takeaways
- The electron is the subatomic particle with a negative electric charge.
- Its charge is −1.602176634 × 10⁻¹⁹ coulombs, or −1 elementary charge NIST CODATA.
- Protons are positive, neutrons are neutral, and electrons are negative.
- Electrons are attracted to protons because opposite electric charges attract.
- A neutral atom has equal numbers of protons and electrons.
