An electron is a negatively charged subatomic particle and a fundamental component of atoms, responsible for electricity, chemical bonding, and many physical phenomena. Atoms consist of protons, neutrons, and electrons. Of these three particles, the electron has the smallest mass. Here is the definition of the electron, along with its word origin, history, and interesting facts.
Key Takeaways: Electron
- An electron is a negatively charged subatomic particle found in atoms and in free form.
- Electrons are elementary particles belonging to the lepton family.
- They have a charge of −1.602 × 10⁻¹⁹ C and a mass of 9.11 × 10⁻³¹ kg.
- Electrons occupy orbitals (probability regions) rather than fixed paths.
- They are responsible for chemical bonding, electricity, and magnetism.
- Electrons exhibit wave-particle duality and follow the rules of quantum mechanics.
- The electron’s antiparticle is the positron.
Electron Definition
An electron is a stable subatomic particle with a negative electrical charge. Unlike protons and neutrons, electrons are not constructed from even smaller components. Each electron carries one unit of negative charge (1.602 x 10-19 coulomb) and has a very small mass as compared with that of a neutron or proton. The mass of an electron is 9.10938 x 10-31 kg. This is about 1/1836 the mass of a proton.
A common symbol for an electron is e–. The electron’s antiparticle, which carries a positive electric charge, is called a positron or antielectron. A positron is denoted using the symbol e+ or β+. When an electron and a positron collide, both particles are annihilated and energy is released in the form of gamma rays.
Electron vs Proton vs Neutron
Atoms contain three main subatomic particles, but they differ significantly in their properties and roles. Comparing electrons, protons, and neutrons side by side highlights how charge, mass, and location determine atomic structure, chemical behavior, and physical properties. Understanding these differences helps explain why atoms form bonds, how elements are identified, and how matter behaves at the most fundamental level.
| Property | Electron | Proton | Neutron |
|---|---|---|---|
| Charge | −1 | +1 | 0 |
| Mass (kg) | 9.11 × 10⁻³¹ | 1.67 × 10⁻²⁷ | 1.67 × 10⁻²⁷ |
| Location | Orbitals | Nucleus | Nucleus |
| Type | Lepton | Baryon | Baryon |
Where to Find Electrons
Electrons exist both as bound particles within atoms and as free particles in space and materials. In atoms, electrons do not orbit the nucleus like planets. Instead, quantum mechanics describes them as existing in orbitals, which are regions of space where there is a high probability of finding an electron.
Orbitals have different shapes, including spherical (s orbitals), dumbbell-shaped (p orbitals), and more complex forms. The exact position of an electron cannot be known precisely due to the Heisenberg Uncertainty Principle.
Free electrons occur in plasmas, metals, and vacuum tubes. In metals, electrons move through a lattice of atoms and enable electrical conductivity.
History and Word Origin
The possibility of electrons was predicted by Richard Laming (1838-1851), Irish physicist G. Johnstone Stoney (1874), and other scientists. The term “electron” was first suggested by Stoney in 1891, although the electron was not discovered until 1897, by British physicist J.J. Thomson.
Although electron sciences dates to the 19th and 20th centuries, the words “electron” and “electricity” trace their origins to the ancient Greeks. The ancient Greek word for amber was elektron. The Greeks noticed rubbing fur with amber caused the amber to attract small objects. This is the earliest recorded experimentation with electricity. The English scientist William Gilbert coined the term “electricus” to refer to this attractive property.
Key Milestones in Electron Discovery
- 1838–1851: Richard Laming proposes atomic structure involving charged particles
- 1874: George Johnstone Stoney estimates unit of electric charge
- 1891: Stoney coins the term “electron”
- 1897: J. J. Thomson discovers the electron using cathode rays
- 1909: Robert Millikan measures electron charge
- 1926: Erwin Schrödinger develops wave equation
Electron Structure and Properties
Understanding electrons requires more than knowing their charge and mass. Scientists describe electrons in terms of both their measurable physical properties and their underlying structure as fundamental particles. Although electrons are considered elementary, meaning they are not made of smaller components, they still exhibit complex behavior governed by quantum mechanics. Their properties, such as charge, mass, spin, and wave-like nature, determine how they interact with electric and magnetic fields, how they form chemical bonds, and how they behave in atoms and materials.
Electron Properties
| Property | Value |
|---|---|
| Symbol | e⁻ |
| Charge | −1.602 × 10⁻¹⁹ C |
| Mass | 9.109 × 10⁻³¹ kg |
| Spin | 1/2 |
| Particle Type | Lepton |
| Classification | Elementary particle |
| Antiparticle | Positron (e⁺) |
Electron Configuration and Chemical Behavior
Electrons determine how atoms interact. The arrangement of electrons in orbitals, called the electron configuration, controls chemical properties.
Atoms tend to gain, lose, or share electrons to achieve a stable configuration, often resembling the nearest noble gas. This leads to:
- Ionic bonds (electron transfer)
- Covalent bonds (electron sharing)
- Metallic bonding (delocalized electrons)
Valence electrons, which occupy the outermost shell, play the largest role in chemical reactions.
Electrons in Quantum Mechanics
Quantum mechanics provides the most accurate description of electrons. Instead of fixed paths, electrons are described by wavefunctions, which give the probability of finding an electron in a particular location.
Electrons exhibit wave-particle duality, meaning they behave as both particles and waves. Experiments such as the double-slit experiment demonstrate that electrons can produce interference patterns, a property of waves.
Electrons in atoms are organized into energy levels and orbitals, defined by quantum numbers:
- Principal quantum number (n)
- Angular momentum (l)
- Magnetic (mₗ)
- Spin (mₛ)
These quantum properties determine chemical behavior and bonding.
Electrons and Electricity
Electric current is the flow of electric charge, usually carried by electrons in conductive materials. In metals, electrons move through a lattice of positive ions with minimal resistance.
In electrolytes and plasmas, ions carry charge instead of electrons. The movement of electrons also generates magnetic fields, linking electricity and magnetism through electromagnetism.
Electron Facts
- Electrons are considered to be a type of elementary particle because they are not made up of smaller components. They are a type of particle belonging to the lepton family and have the smallest mass of any charged lepton or other charged particle.
- In quantum mechanics, electrons are considered to be identical to each other because no intrinsic physical property may be used to distinguish between them. Electrons may swap positions with each other without causing an observable change in a system.
- Protons and electrons have equal, but opposite charges. Electrons are attracted to positively-charged particles, such as protons.
- Whether or not a substance has a net electric charge is determined by the balance between the number of electrons and the positive charge of atomic nuclei. If there are more electrons than positive charges, a material is said to be negatively charged. If there is an excess of protons, the object is considered to be positively charged. If the number of electrons and protons is balanced, a material is said to be electrically neutral.
- Electrons in a metal behave as if they were free electrons and can move to produce a net flow of charge termed an electric current. When electrons (or protons) move, a magnetic field is generated.
- Electrons have properties of both particles and waves. They can be diffracted, like photons, yet can collide with each other and other particles, like other matter.
- Atomic theory describes electrons as surrounding the proton/neutron nucleus of an atom in shells. These shells are regions of probability. Some are spherical, but other shapes also occur. While it’s theoretically possible to find an electron in the atomic nucleus, the highest probability of finding one is within its shell.
- An electron has a spin or intrinsic angular momentum of 1/2.
- Scientists are capable of isolating and trapping a single electron in a device called a Penning trap.
- From examining single electrons, researchers have found the largest electron radius is 10-22 meters. Because electrons are very small, they are treated like point charges, which are electrical charges with no physical dimensions.
- Matter is much more abundant than antimatter in the universe, but there may once have been equal numbers of electrons and positrons. According to the Big Bang theory, photons gained enough energy within the first millisecond of the explosion to react with each other to form electron-positron pairs. These pairs annihilated each other, emitting photons. For unknown reasons, there came a time when there were more electrons than positrons and more protons than antiprotons. The surviving protons, neutrons, and electrons began to react with each other, forming atoms.
- Electrons are used in many practical applications. These include electricity, vacuum tubes, photomultiplier tubes, cathode ray tubes, particle beams for research and welding, and the free-electron laser.
Common Misconceptions About Electrons
- Electrons do not orbit the nucleus like planets, they exist in probability clouds.
- Electrons are not tiny solid spheres, they behave as quantum objects.
- Electrons do not lose energy and spiral into the nucleus in stable atoms.
- Current does not always involve electrons, ions can carry charge too.
FAQs About Electrons
Can electrons exist independently?
Yes, free electrons exist in plasmas, vacuum tubes, and metals.
Do electrons have size?
Electrons are treated as point particles, with no measurable physical size.
Why don’t electrons fall into the nucleus?
Quantum mechanics restricts electrons to specific energy states.
Are electrons matter or energy?
Electrons are matter particles, but they also exhibit wave-like properties.
References
- Buchwald, J.Z.; Warwick, A. (2001). Histories of the Electron: The Birth of Microphysics. MIT Press. pp. 195–203. ISBN 978-0-262-52424-7.
- Thomson, J.J. (1897). “Cathode Rays”. Philosophical Magazine. 44 (269): 293–316. doi:10.1080/14786449708621070