An electron is one of the three fundamental subatomic particles that constitute atoms, alongside protons and neutrons. Electrons carry a negative electric charge, which is considered the basic unit of electric charge. They orbit the atom's nucleus, which contains positively charged protons and neutral neutrons. Electrons are the lightest charged particles known and are essential for chemical bonding and reactions, making life possible. Discovered in 1897 by J.J. Thomson, the electron's existence revealed that atoms have a complex structure, challenging previous notions of indivisible particles.

Where are electrons found in an atom?

Electrons are found in shells, which are regions surrounding an atom's nucleus. These shells are assigned quantum numbers, with n =1 being the closest to the nucleus and higher numbers indicating greater distance. Each shell contains orbitals, and within these orbitals, electrons move in probability distributions known as electron clouds. The arrangement of electrons in these shells and orbitals determines an atom's chemical properties. The number of electrons in the outermost shell, the valence shell, is particularly important for chemical activity.

What is the electric charge of an electron?

The electric charge of an electron is a fundamental constant, symbolized as e . It has a value of 1.602176634 × 10-19 coulombs . This charge is negative, making the electron the basic unit of negative electric charge. All freely existing charged subatomic particles have a charge equal to this value or a whole-number multiple of it. Quarks, which are components of particles like protons and neutrons, have charges that are fractions (1/3 or 2/3) of this fundamental value. The electron was discovered in 1897 by J.J. Thomson, revolutionizing the understanding of atomic structure.

How do electrons move around the nucleus of an atom?

Electrons do not orbit the nucleus of an atom in the same way planets orbit the sun. Instead, electrons exist in specific regions of probability around the nucleus called orbitals, which are organized into energy levels or shells. These orbitals are described by mathematical wave functions. Electrons can move between these energy levels through a process called a quantum leap, where they absorb or emit energy in the form of photons. This movement is not a continuous path but rather an instantaneous disappearance from one orbital and reappearance in another. Electrons also possess an intrinsic property called spin, which can be oriented in one of two directions.

Why are electrons important in forming chemical bonds?

Electrons are crucial in forming chemical bonds because the outermost electrons, known as valence electrons, are involved in these interactions. These valence electrons are less tightly bound to the atom's nucleus compared to inner electrons, allowing them to be shared or transferred between atoms. This sharing or transfer of valence electrons is the basis of ionic and covalent bonds, which hold atoms together to form molecules and compounds. The energy required to remove these valence electrons, known as ionization energy, plays a significant role in determining an atom's ability to form bonds.

How do electrons affect electricity and magnetism?

Electrons, as negatively charged subatomic particles, are fundamental to both electricity and magnetism. Their movement constitutes an electric current, which in turn generates a magnetic field. Conversely, moving charges experience a force when in a magnetic field. Electrons also possess an intrinsic property called spin, which makes them behave like tiny magnets, each with its own magnetic moment. The collective behavior of these electron magnetic moments within atoms determines the magnetic properties of materials, leading to phenomena like paramagnetism and ferromagnetism. Ultimately, electricity and magnetism are two facets of a unified phenomenon known as electromagnetism.

electron

Introduction References & Edit History Quick Facts & Related Topics

Images & Videos

Bohr model of a fluorine atom showing a central cluster of red and yellow spheres for protons and neutrons, with blue electrons orbiting in two rings.

Illustration of an atom showing a central nucleus with multiple electrons orbiting in concentric shells, representing electron arrangement in atoms.

A diagram showing atomic energy levels and electron orbitals, with labeled boxes for s, p, d, and f orbitals from levels 1 to 7, and arrows indicating the order of electron filling. Some higher orbitals are shaded to show they are not occupied by ground-state electrons.

electron density functions for four hydrogen atom states

Diagram showing electron density shapes for atomic orbitals: A spherical s orbital at the top left, and three dumbbell-shaped p orbitals oriented along the x, y, and z axes below, each with labeled axes.

Diagram comparing atomic structure models: on the left, the Bohr model shows electrons orbiting a nucleus in labeled energy levels; on the right, wave mechanics depict electron wave patterns around the nucleus.

A diagram showing an X-ray photon colliding with an electron, causing the electron to scatter and the photon to emerge with a longer wavelength, illustrating the Compton effect.

Quick Facts

Key People:: P.A.M. Dirac; J.J. Thomson; Louis de Broglie; Richard Henderson; Jacques Dubochet

Related Topics:: solvated electron; magnetization electron; electron pair; secondary electron; recoil electron

See all related content

electron

subatomic particle

Also known as: negative electron

Written and fact-checked by

Britannica Editors

Last updated

Nov. 12, 2026 •History

News •

A hidden limit of space and time could unlock electronics 100,000 times faster • Nov. 7, 2026, 6:35 PM ET (Science Daily)

Discord is ditching Electron and its new app uses less RAM • Nov. 5, 2026, 6:39 AM ET (The Verge)

Electrical guardrails for charge carriers: A new approach to harness graphene for solar cells • Oct. 29, 2026, 7:20 PM ET (Phys.org)

An 'electron waiting room' helps blue titanium dioxide hold light energy longer • Oct. 26, 2026, 10:20 AM ET (Phys.org)

Top Questions

What is an electron?
An electron is one of the three fundamental subatomic particles that constitute atoms, alongside protons and neutrons. Electrons carry a negative electric charge, which is considered the basic unit of electric charge. They orbit the atom's nucleus, which contains positively charged protons and neutral neutrons. Electrons are the lightest charged particles known and are essential for chemical bonding and reactions, making life possible. Discovered in 1897 by J.J. Thomson, the electron's existence revealed that atoms have a complex structure, challenging previous notions of indivisible particles.
8 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Where are electrons found in an atom?
Electrons are found in shells, which are regions surrounding an atom's nucleus. These shells are assigned quantum numbers, with n=1 being the closest to the nucleus and higher numbers indicating greater distance. Each shell contains orbitals, and within these orbitals, electrons move in probability distributions known as electron clouds. The arrangement of electrons in these shells and orbitals determines an atom's chemical properties. The number of electrons in the outermost shell, the valence shell, is particularly important for chemical activity.
8 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What is the electric charge of an electron?
The electric charge of an electron is a fundamental constant, symbolized as e. It has a value of 1.602176634 × 10^-19 coulombs. This charge is negative, making the electron the basic unit of negative electric charge. All freely existing charged subatomic particles have a charge equal to this value or a whole-number multiple of it. Quarks, which are components of particles like protons and neutrons, have charges that are fractions (1/3 or 2/3) of this fundamental value. The electron was discovered in 1897 by J.J. Thomson, revolutionizing the understanding of atomic structure.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do electrons move around the nucleus of an atom?
Electrons do not orbit the nucleus of an atom in the same way planets orbit the sun. Instead, electrons exist in specific regions of probability around the nucleus called orbitals, which are organized into energy levels or shells. These orbitals are described by mathematical wave functions. Electrons can move between these energy levels through a process called a quantum leap, where they absorb or emit energy in the form of photons. This movement is not a continuous path but rather an instantaneous disappearance from one orbital and reappearance in another. Electrons also possess an intrinsic property called spin, which can be oriented in one of two directions.
11 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Why are electrons important in forming chemical bonds?
Electrons are crucial in forming chemical bonds because the outermost electrons, known as valence electrons, are involved in these interactions. These valence electrons are less tightly bound to the atom's nucleus compared to inner electrons, allowing them to be shared or transferred between atoms. This sharing or transfer of valence electrons is the basis of ionic and covalent bonds, which hold atoms together to form molecules and compounds. The energy required to remove these valence electrons, known as ionization energy, plays a significant role in determining an atom's ability to form bonds.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do electrons affect electricity and magnetism?
Electrons, as negatively charged subatomic particles, are fundamental to both electricity and magnetism. Their movement constitutes an electric current, which in turn generates a magnetic field. Conversely, moving charges experience a force when in a magnetic field. Electrons also possess an intrinsic property called spin, which makes them behave like tiny magnets, each with its own magnetic moment. The collective behavior of these electron magnetic moments within atoms determines the magnetic properties of materials, leading to phenomena like paramagnetism and ferromagnetism. Ultimately, electricity and magnetism are two facets of a unified phenomenon known as electromagnetism.
9 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

electron, one of the three basic subatomic particles—along with protons and neutrons—that make up atoms, the basic building blocks of all matter and chemistry. The negatively charged electrons circle an atom’s central nucleus, which is formed by positively charged protons and the electrically neutral particles called neutrons. (The nucleus of the ordinary hydrogen atom is an exception, containing only one proton and no neutrons.) Like opposite ends of a magnet that attract one another, the negative electrons are attracted to a positive force, which binds them to the nucleus. The nucleus is small and dense compared with the electrons, which are the lightest charged particles in nature. The electrons circle the nucleus in orbital paths called shells, each of which holds only a certain number of electrons.

The electron was discovered in 1897 by the English physicist J.J. Thomson during investigations of cathode rays. His discovery of electrons, which he initially called corpuscles, played a pivotal role in revolutionizing knowledge of atomic structure. Under ordinary conditions electrons are bound to the positively charged nuclei of atoms by the attraction between opposite electric charges. In a neutral atom the number of electrons is identical to the number of positive charges on the nucleus. Any atom, however, may have more or fewer electrons than positive charges and thus be negatively or positively charged as a whole; these charged atoms are known as ions. Not all electrons are associated with atoms; some occur in a free state with ions in the form of matter known as plasma.

Within any given atom, electrons move about the nucleus in an orderly arrangement of orbitals, the attraction between electrons and nucleus overcoming repulsion among the electrons that would otherwise cause them to fly apart. These orbitals are organized in concentric shells proceeding outward from the nucleus with an increasing number of subshells. The electrons in orbitals closest to the nucleus are held most tightly; those in the outermost orbitals are shielded by intervening electrons and are the most loosely held by the nucleus. As the electrons move about within this structure, they form a diffuse cloud of negative charge that occupies nearly the entire volume of the atom. The arrangement of electrons in orbitals and shells around the nucleus is referred to as the electronic configuration of the atom. This electronic configuration determines not only the size of an individual atom but also the chemical activity of the atom. The classification of elements within groups of similar elements in the periodic table, for example, is based on the similarity in their electron structures.

Periodic Table of the elements concept image (chemistry)

Britannica Quiz

Facts You Should Know: The Periodic Table Quiz

Within the field of particle physics, there are two ways of classifying electrons. The electron is a fermion, a type of particle named after the Fermi-Dirac statistics that describe its behaviour. All fermions are characterized by half-integer values of their spin, where spin corresponds to the intrinsic angular momentum of the particle. The concept of spin is embodied in the wave equation for the electron formulated by P.A.M. Dirac. The Dirac wave equation also predicts the existence of the antimatter counterpart of the electron, the positron. Within the fermion group of subatomic particles, the electron can be further classified as a lepton. A lepton is a subatomic particle that reacts only by the electromagnetic, weak, and gravitational forces; it does not respond to the short-range strong force that acts between quarks and binds protons and neutrons in the atomic nucleus.

The lightest stable subatomic particle known, the electron carries a negative charge of 1.602176634 × 10⁻¹⁹ coulomb, which is considered the basic unit of electric charge. The rest mass of the electron is 9.1093837015 × 10⁻³¹ kg, which is only 1/1,836the mass of a proton. An electron is therefore considered nearly massless in comparison with a proton or a neutron, and the electron mass is not included in calculating the mass number of an atom.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Meg Matthias.

electron

News •

Thank you for signing up!