From the earliest times, man has always wondered about the ultimate nature of matter. He has searched to establish the basic constituents of all the substances.
With the development of more scientific ideas on elements, compounds and mixtures, people began to probe into how and why substances react.
Atom was derived from the Greek word 'atoms', meaning 'indivisible'. Thus, it was considered to be indivisible.Atoms of the same element are identical in shape, size, mass and other properties.Atoms cannot be created, divided or destroyed during any chemical or physical change.
An atom having a charge on it is called an ion. When an atom loses or gains charge, it gets converted into a positively or negatively charged ion respectively.
Every chemical substance is known by a specific name. But these names can sometimes be cumbersome, confusing and not provide sufficient information about its chemical composition.
The molecular mass of a substance is the relative mass of its molecule as compared with the mass of a 12C atom taken as 12-units.
1 mole of an atom = 1 gram atomic weight of an atom.
According to Dalton's atomic theory, all matter is made up of very small particles called atoms, which cannot be further divided and have independent existence.