1 Simple molecules [molecule: A molecule is a collection of two or more atoms held together by chemical bonds. 2  It is the smallest part of a substance that displays the properties of the substance.
Eon has a number of meanings. In Astronomy, an eon refers to 1 billion (109) years. But it also refers to a very long, unspecified period of time, or specific geologic stages of the Earth.
An eon does not have a specific span of years, but is generally recognized as being around 1000-years. It is a long span of geologic time. Eons are longer periods of time than eras. An eon does not have a specific span of years, but is generally recognized as being around 1000-years. It is a long span of geologic time. Eons are longer periods of time than eras.