Discovered by J.J. Thomson (British physicist) in 1897, an electron is a negatively charged particle, found encircling an atom’s nucleus. In other words, an electron is a subatomic particle that makes up an atom – along with the nucleus, protons and neutrons. An atom can have anywhere between 1 and 100 or more electrons. An electron is elementary and cannot be further subdivided into other particles.
Electrons are found surrounding the nucleus in spherical electron shells and with varying radiuses or radii. The different shells represent varying energy levels. The farther the shell from the nucleus, the stronger is the energy of the electrons located in those shells. Also, different energy levels house a specific number of electrons. The first shell (the one closest to the nucleus) holds two electrons. The second shell can have no more than eight electrons, and so on. Therefore, the number of energy shells of an atom depend on how many electrons the atom has. For example, uranium atom – the biggest naturally available atom – has 92 electrons and needs seven shells to hold its electrons in place.
Size and Bonding
An electron is the smallest subatomic particle, when compared to protons and neutrons. Its mass is 9.1 x 10-31 kilograms. In fact, an electron is 1/1835 the size of a proton. Since an electron is unbelievably minute, its mass is measured in atomic mass units, and not grams. Electrons are in constant motion in their shells, making it difficult to determine their actual position, at any given time. Not to mention, electrons play a major role in every type of chemical bonding – be it an ionic bond, covalent bond, or a metallic bond. Electrons and current electricity are also closely associated. In other words, current flow takes place due to the individual movement of an electron from one atom to another.