The Earth and everything dwelling on it like humans, animals, birds, plants, trees, water, air, mountains, and the like is composed of matter that occupies space and has some mass.
Matter is made up of substances called elements and there are 118 elements and each of which is composed of very small units called Atoms. Atoms itself are composed of electrons, protons and neutrons.
Electron has a negative charge; proton has a positive charge while a neutron has no charge at all.
Most of the elements are designated by their chemical symbol, which is a single begining letter. Or, when the first letter is already taken by another element then a combination of two beginning letters gives it a name, for example, C for carbon and Ca for calcium, O for oxygen. Other elements’ chemical symbols come from their Latin names; for example, the symbol for sodium is Na, which is a short form of natrium, the Latin word for sodium.
There are four elements common to all living organisms like oxygen (O), carbon (C), hydrogen (H), and nitrogen (N), which together make up about 96% of the human body. Among these elements present in the living organisms, some are very rare to be found on earth. However, in the non-living world, elements are found in different proportions.
