Atomic Models

All electrical states and processes are linked to the presence of the tiniest of all elementary particles that is known as an electron.

An electron carries a charge that corresponds to the smallest amount of electrical charge it is possible to have. It is the elementary quantum of electricity.

Electrons are a constituent of the atoms that make up any chemical element. An atom (from the Greek atomos, meaning irreducible) was long thought to be the ultimate irreducible component of matter. Nowadays it is known that atoms are not irreducible. They actually possess a rather complex structure that we have tried to envisage using atomic models. The atomic model developed by Niels Bohr is still the most important of these. It perceives the structure of an atom as being in the nature of our solar system. At the centre lies the atomic nucleus in the way that the sun lies at the centre of the solar system. Electrons then move in orbit around this nucleus like planets. Atoms of various elements differ in terms of the size of the nucleus and the number of electrons that surround it. The electron orbits can be elliptical or circular and are of differing diameter and in differing planes. They make up the shell of the atom. The diameter of an atomic nucleus is about 10,000 times smaller than the diameter of the atom as a whole.

Atoms consist of an atomic nucleus and an electron shell.

Electrons are negatively charged while the nucleus is composed of uncharged neutrons and positively charged protons. Its overall charge is thus positive. For this reason, an atom should possess an equal number of electrons and protons to make it electrically neutral. The following graphic depicts the atomic model in its entirety. 

The simplest atom is that of the lightest element hydrogen. This has only one electron orbiting a single proton with no neutrons at all. An atom of oxygen, for example, would possess eight electrons, two in an inner orbital shell and six further out. An aluminium atom contains 13 electrons in three different orbital shells of differing diameter. The heaviest atom known to occur naturally is that of uranium, which has 92 electrons in seven separate orbital shells. The following graphic depicts simplified models of the hydrogen, oxygen and aluminium atoms. The orbits are shown as if they were circular and in the same plane for simplicity's sake and the structures of the nuclei themselves are also omitted. 

Each electron orbit can only accommodate a specific maximum number of of electrons. The innermost orbital shell can only contain two electrons, the next layer has a maximum of eight and the third takes up to 18.

More From