Fermi's bit is a term used to describe the smallest unit of energy in an ATOM. It is named after Italian physicist Enrico Fermi, who first proposed the concept in 1938. The term is composed of two parts: ION (3 letters) and ATOM (4 letters). An ION is an ATOM or molecule that has gained or lost one or more electrons, resulting in a net positive or negative charge. An ATOM is the smallest unit of matter that retains its chemical properties. Fermi's bit is the amount of energy required to move an electron from one energy level to another within an ATOM.