Electron

An electron is an extremely small particle carrying a negative electrical charge. It is one of three primary components of an atom, alongside the proton and neutron. Electrons orbit around the nucleus of the atom, where protons and neutrons are located.

The mass of an electron is very small compared to that of a proton—approximately one thirteen-hundredth of a proton's mass. As physics currently understands it, the electron has no smaller component (it is fundamental) and is classified as a member of the group known as leptons.

History of Discovery

The electron was identified in the late 19th century through experiments with evacuated tubes (cathode ray tubes). In 1897, the English physicist J. J. Thomson measured the charge-to-mass ratio of these rays and concluded that they consisted of particles smaller than atoms. The term 'electron' itself had already been proposed to denote the fundamental unit of electrical charge.

Properties

The electron carries a negative electrical charge equal in magnitude to—but opposite to—that of the proton. It also possesses a property called spin, which makes it subject to the rules governing fermions: two electrons in the same atom cannot occupy the same quantum state. This principle (Pauli exclusion) determines how electrons are arranged in shells around the atom.

Dual Nature

In quantum physics, the electron is not understood merely as a small orbiting sphere. It exhibits both particle and wave properties. Diffraction experiments have shown that electrons interfere with each other like waves. Therefore, the location of an electron is described in terms of probability (probability distribution), known as an orbital, rather than as a definite path.

Role in Chemistry and Electricity

Chemical bonding between substances depends on electrons in the outer shell of an atom. Atoms can share or transfer electrons to each other, forming covalent or ionic bonds. The flow of electric current in metals and electronic devices results from the movement of free electrons.