Electron
Introduction
The electron is a subatomic particle that carries a negative electric charge. It is one of the fundamental particles of the universe, and its properties are crucial in many areas of physics and chemistry.
History
The electron was first identified as a distinct particle in the late 19th century. The term 'electron' was first proposed by the Irish physicist George Johnstone Stoney in 1891, and the particle itself was discovered by J.J. Thomson in 1897 during his work on cathode rays. Thomson's discovery of the electron disproved the then-prevailing theory that atoms were indivisible and led to the development of the plasma model of the atom.
Physical Properties
Electrons are point particles; they do not have any physical size or shape. They have a rest mass of approximately 9.10938356 × 10−31 kilograms, which is about 1/1836 of the mass of a proton. Electrons carry a negative electric charge of −1.602176634 × 10−19 coulombs.
Behaviour and Interactions
Electrons exhibit both particle-like and wave-like behaviour, a phenomenon known as wave–particle duality. This is a fundamental concept in quantum mechanics, the theory that describes the behaviour of electrons and other subatomic particles.
Electrons interact with other particles through four fundamental forces: gravity, electromagnetism, the strong force, and the weak force. The most significant of these for electrons is electromagnetism, as it is responsible for the electron's electric charge and its interactions with other charged particles.
Role in Atoms
In an atom, electrons occupy a space known as the electron cloud, which surrounds the atom's nucleus. The distribution of electrons in this cloud, and their energies, are described by atomic orbitals, mathematical functions derived from the principles of quantum mechanics.
Electrons play a crucial role in chemical reactions. The sharing or exchange of electrons between atoms is what forms chemical bonds, the forces that hold atoms together in molecules.
Role in Electricity
The movement of electrons is the basis for electric current. When a voltage is applied across a conductor, it creates an electric field that pushes electrons through the material, creating a current. This is the principle behind all electrical devices, from light bulbs to computers.
Role in Magnetism
Electrons are also responsible for magnetism. The magnetic properties of a material depend on the motion of its electrons. In particular, the intrinsic spin of electrons gives rise to a type of magnetism known as ferromagnetism, which is the mechanism behind permanent magnets.
Role in Light
Electrons play a key role in the production of light. When an electron in an atom absorbs energy, it can move to a higher energy level, or orbital. When the electron returns to its original energy level, it releases the energy as a photon of light. This process is responsible for the light emitted by stars, including the sun, and many other light sources.