Atoms and Molecules

Atoms and Molecules

     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.

Laws of Chemical Combination

     With the development of more scientific ideas on elements, compounds and mixtures, people began to probe into how and why substances react.

The Atom

     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.

Formation of Molecule

     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.

Chemical Formulae

     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.

Molecular Mass and Mole Concept

     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.

Numericals Based on Mole Concept

     1 mole of an atom = 1 gram atomic weight of an atom.

Summary

     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.

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