The Atom

Abstract

According to Bohr’s atomic theory, an atom is composed of a nucleus at the center and one or more electrons rotating around the nucleus along different energy orbits. The nucleus is primarily composed of protons and neutrons, collectively called nucléons. For an atom of a given element, the number of electrons moving around the nucleus equals the number of protons, balancing the electrical charge of the nucleus. The size of an atom is of the order of 10^-8 cm (1 angstrom, Å) and that of a nucleus is of the order of 10^-13 cm (equal to a unit termed the fermi, F, in honor of the famous physicist, E. Fermi). The electron configuration of the atom determines the chemical properties of an element, whereas the nuclear structure characterizes the stability and radioactive decay of the nucleus of an atom.