Question

what is a atom? how is help us

Answer 1

it is the smallest part in which elements can be divided

it is used for creating molecules around us

Answer 2

If you want to do a little more thinking, imagine the smallest particles of matter. Super-tiny subatomic particles are used to create the parts of atoms. Protons, neutrons, and electrons can then organize to form atoms. Atoms are then used to create the molecules around us.
The fact that atoms cannot be created or destroyed in chemical reactions allows for all sorts of important predictions. Atoms form the smallest building blocks of chemistry, and they combine to form an infinite variety of more complicated structures, however it turns out atoms are not the smallest pieces of matter.