Earth as a Source of Elements

Most elements are formed due to fusion of simple nuclei to give heavier nuclei i.e., nucleosynthesis or nuclear fusion reactions taking place in the stars. Atoms of these elements began to fall together about six billion years ago to form a system, presently called the solar system. A part of these elements formed in space and such a condensed phase of matter, formed the Earth.

The Earth was a huge molten mass in the initial stages of formation. As this mass cooled, partial solidification and separation of different materials took place. The more easily crystallizable and light materials formed the upper layer called the crust and the molten mass formed the core (central part) of the earth. During cooling, the gases dissolved in the molten mass and escaped out, to form the atmosphere around Earth.

Distribution of various elements in the Earth's crust

Water is one of the most abundant compounds on Earth, hence sea water is a vast source of a large number of elements. The Earth's atmosphere contains mainly nitrogen (78%), oxygen (21%), and other gases e.g., CO₂, He, Ne ( 1% volume)