Electron

An electron is an elementary particle that carries a negative elementary charge −e.

e = 1.602 176 565(35) × 10^-19 C

The electron mass is

m_e= 9.109 382 91(40) × 10⁻³¹ kg.

It has a gyromagnetic ratio

γ_e = 1.760 859 708(39) x 10¹¹ s^-1 T^-1

or a magnetic moment of about −1.00115965 Bohr magneton (μ_B):

μ_B = 927.400 968(20) x 10^-26 J/ T.

Because they have spin 1/2, the behavior of large numbers of electrons is governed by Fermi statistics.

At a very microscopic level, electrons belong to the leptons, one of two types of fundamental particles in the Standard Model of particle physics, the other being the quarks. On a larger scale, atoms and molecules are made up of electrons together with the neutrons and protons of atomic nuclei.

The behavior of electrons at the atomic and molecular level is governed by quantum mechanics or quantum electrodynamics. The (quantum mechanical) interaction between electrons on nearby atoms underlies the chemical bonding in molecules, gases, liquids, and solids such as crystals.

On a larger scale, however, these microscopic considerations often can be approximated as macroscopic currents and charges, which then are used in classical electrodynamics to describe electromagnetic fields using the (classical) Maxwell equations. In such an approach, quantum mechanics can be used to establish the electronic properties of materials, which then are expressed in the macroscopic Maxwell equations by introducing material parameters such as permittivities, permeabilities, conductivities and the like without further need for quantum theory.