What is an atom and expailn

a particle of matter that uniquely defines a chemical element.An atom consists of a central nucleus that is usually surrounded by one or more electrons. Each electron is negatively charged. The nucleus is positively charged, and contains one or more relatively heavy particles known as protons and neutrons.

An atom is the smallest particle of an element that can take part in a chemical reaction.Atoms are so small in size that we cannot see them under the most powerful optical microscope. Their radius is measured in nanometres.Atoms usually exist in the form of molecules or ions.They are made up of 3 subatomic particles: electrons, protons, neutrons.An atom is electrically neutral.It has a nucleus which is a small positively charged part placed in the centre. It is surrounded by circular parts called orbits.

Hope you could understand.

If you have any query, feel free to ask.

The answer for this question is d. none of these