Almost everything on the Earth around us consists of chemical compounds, of a great variety of combinations of the chemical elements.

   Only an insignificant part of terrestrial matter is in the form of elemental substances, namely: the noble gases, the platinum metals, carbon in its various forms, and that is about all.

   Possibly, a very long time ago the clot of cosmic matter which finally became our planet, consisted all of only the atoms of almost l00 chemical elements. Hundreds, thousands, millions of years passed. Conditions changed. The atoms reacted with one another. The gigantic laboratory of nature began to operate. During its long evolution nature, the chemist, learned to prepare all kinds of substances, from the simple water molecule to infinitely complex proteins. 

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