ATOMS AND MOLECULES

What is an Atom?

For many years, people  have wondered what matter is made up of. Some ancient Greek  philosophers believed  that all matter was made up of four substances, namely earth, water, air and fire. Ancient Chinese philosophers believed that matter was made up of  gold, wood, water, fire and earth. About 430 B.C., a Greek philosopher named Democritus suggested that  matter was made up of  indivisible particles called atoms. This came from the Greek word 'atomos' , meaning 'indivisible'. He believed that nothing could be smaller than an atom.

An atom is defined as the smallest existing particle. They are the building blocks of  all matter.

All matter, living or non-living, is made up of atoms. Atoms are so small that you cannot see them with an  ordinary microscope. It can only be seen through a special microscope. A single atom measures only about  1/10 000 000 mm across. More than 10 000 000 000 000 (ten trillion) atoms would  be needed to cover the full stop at the end of this sentence.

Each element is made up of its own type of atom. Carbon is made up of  its identical carbon atoms, same as this iron is made up of iron atoms. The atoms of different chemicals are not of the same size.