Abstract
Chemistry is all about atoms and the interactions between these atoms to form molecules that make up the world. According to cosmologists, the universe began with the Big Bang approximately 13.8 billion years ago. This is considered to be the age of the universe. After the initial expansion, the universe eventually cooled sufficiently to allow the formation of subatomic particles: quarks, electron, proton, neutron, etc., and, later on, atoms of simple elements. Modern chemistry began with the discovery of nitrogen and oxygen, the two principal components of air. Nitrogen and oxygen are the main components of air, comprising 78" and 21" of the atmosphere, respectively. John Dalton's atomic theory spawns the beginning of modern chemistry. The theory states that matter consists of indivisible particles called atoms and that atoms of a given element are all identical and can neither be created nor destroyed. Compounds are formed by combination of atoms in simple ratios to give compound atoms.