Matter - Atoms and Molecules

We see many things around us such as a table, chair, book, glass, hills, mountains, river, birds, animals, sun, moon and stars. All the objects seen around us are either born naturally or made by humans.

For example, the hill is made up of rocks; the book is made of paper. Similarly, all are made up of some material. 

All the things that you can see or cannot see, but can experience them, they are called substances. All these things have some weight and they also cover the area of some places. Hence, a substance can be defined as: "Any object that carries a load and the space it occupies is called a substance."

Composition of Matter

If we break a small piece of iron until it is broken into such a small part that it cannot be broken any further, then even this small piece of iron has all the properties of iron present in it. Therefore, we can say that any substance consists of the same type of particles.


All the substances found around us are of different types. They all have different color, smell, taste, size.

If we break a mountain, then we will get big rocks. If you break them too, you will get small pieces and if you keep breaking more, then small particles of sand will be found. You will see that the same properties are found in these small particles which are in a rock. Therefore, we can say that a mountain is formed by mixing small particles of sand.

If you try to break even a small particle of this sand, then it can be broken into very small particles. In 1808, a scientist named Dalton, while studying the structure of matter, told that such fine particles of any substance, which have all the basic properties of matter, are called atoms.

Thus, we can say that all matter is made up of atoms. Hence, an atom is the smallest component of a substance that has all the properties of that substance.

An atom is that small particle of a substance, in which all the properties of that substance are present. But atoms can be further divided, but the properties of the particles obtained from it can also be different from the properties of the original material.

Structure of the Atom

Gradually various discoveries revealed that atoms can be further subdivided. The center of an atom has a nucleus consisting mainly of protons and neutrons. Electrons revolve around this nucleus. Atoms of different elements have different structures. This is shown in Figure 1.1 below: 


Atoms of the same substance combine to form molecules. This molecule is the smallest part of any substance that can live independently.

For example, a molecule of water is formed by joining two atoms of hydrogen and one atom of oxygen. Therefore, the smallest particle of a substance which has all the properties of that substance and which can remain in an independent state is called a molecule of that substance.

Atoms combine to form molecules. A molecule of hydrogen is made up of two atoms of hydrogen. This is why so many substances are found all around us, which form many types of substances.