Explain breifly the present state of Atomic-Molecular theory of matter.

It can be summarized as follows:
1. Matter is made up of extremely small particles called molecules which may have independent existence. Molecules themselves are composed of two or more atoms. However, molecules of noble gases are composed of one atom only.
2. Molecules of a particular substance are identical in all respects such as mass, size, shape and other properties.
3. Molecules of different substances have different masses, sizes, shapes and other properties.
4. Molecular mass of a substance is the sum of the atomic masses of the constituent atoms.
5. During a chemical reaction, the molecules of the reacting substances first break into atoms and then recombine to form new molecules of the products.
6. The number of atoms present in one molecule of an element is known as atomicity of the element.