What Is An Atom? 

Image credit - Google.com

An atom is the smallest particle of an element that is not found in the free state.  

Image credit - Google.com

For example, atoms of gold, silver, platinum, etc. take part in chemical reactions

Image credit - Google.com

But it does not split in chemical reactions. 

Image credit - Google.com

It is the smallest particle of the element – Cl, H, N, etc. 

Image credit - Google.com

Dalton's Atomic Model - 

Image credit - Google.com

In 1808, a scientist named John Dalton presented his ideas regarding the atomic structure. 

Image credit - Google.com

This is called Dalton's atomism

Image credit - Google.com

According to this principle, all the properties of matter are inherent in an atom.