Electron
An electron is a negatively charged subatomic particle that occupies the space around an atom's nucleus in regions called orbitals or electron shells, with a charge of -1 elementary charge and a mass of 9.109 × 10⁻³¹ kg (about 1/1836 the mass of a proton). Electrons govern chemical bonding, electrical conductivity, and the optical properties of matter by determining how atoms interact with one another. In a neutral atom, the number of electrons equals the number of protons.
Key Formula
E = hν (Energy of a photon emitted when an electron transitions between energy levels)
LaTeX: E = h\nu
| Symbol | Meaning | Unit |
|---|---|---|
| E | Energy of emitted/absorbed photon | Joules (J) |
| h | Planck's constant (6.626 × 10⁻³⁴) | J·s |
| ν | Frequency of emitted/absorbed light | Hz |
Worked Example
Problem
An electron in a hydrogen atom transitions and emits light at a frequency of 4.57 × 10¹⁴ Hz. What is the energy of this photon?
Solution
Step 1: Use E = hν. Step 2: h = 6.626 × 10⁻³⁴ J·s, ν = 4.57 × 10¹⁴ Hz. Step 3: E = 6.626 × 10⁻³⁴ × 4.57 × 10¹⁴. Step 4: E = 3.028 × 10⁻¹⁹ J.
Answer
Energy of the photon = 3.03 × 10⁻¹⁹ J (this corresponds to visible blue-green light).
Properties of the Electron
| Property | Value | Unit |
|---|---|---|
| Charge | -1 | Elementary charge (e) |
| Mass | 9.109 × 10⁻³¹ | kg |
| Mass (amu) | 0.000549 | u |
| Location | Electron shells/orbitals | — |
| Spin | 1/2 | ħ |
| Classification | Lepton (fundamental particle) | — |
Interactive Tools
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Related Terms
Electron Configuration
Electron configuration is the distribution of electrons of an atom or molecule among its atomic orbitals, described by the principal quantum number (n), sublevel (s, p, d, f), and the number of electrons in each sublevel. Electron configuration determines how an element behaves chemically — its valence electrons (outermost shell) govern reactivity, oxidation states, and bonding capacity. The Aufbau principle, Pauli exclusion principle, and Hund's rule govern how electrons fill orbitals.
Atomic Number
The atomic number (symbol Z) is the number of protons in the nucleus of an atom and uniquely identifies the chemical element — all atoms of the same element have the same atomic number. In a neutral atom, the atomic number also equals the number of electrons, which determines the element's chemical behavior, reactivity, and position on the periodic table. The atomic number ranges from 1 (hydrogen) to 118 (oganesson) for currently known elements.
Ion
An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a net electric charge — positive ions (cations) form when electrons are lost, and negative ions (anions) form when electrons are gained. Ions play a fundamental role in chemical bonding (ionic compounds), electrochemistry, biological processes (nerve impulses rely on Na⁺ and K⁺ ions), and analytical chemistry. The charge of an ion is written as a superscript, such as Ca²⁺ or Cl⁻.
From Greek "elektron" meaning "amber", referring to the static electricity produced when amber is rubbed. The electron was discovered by J.J. Thomson in 1897 through cathode ray experiments. The term "electron" was proposed by Irish physicist George Johnstone Stoney in 1891.