Answer:
Atom
Step-by-step explanation:
An atom is basic unit of all the matter.
Matter can be an element, which has only single kind of atom in it. It is pure form of matter. For example gold is an element and has single kind of atom with same atomic numbers.
Matter can be a compound, which has two or more kinds of atoms.
Example water.
Neutron, proton and electron are sub atomic particles. Electrons are present around a central unit of atom known as nucleus.
Nucleus contains protons and neutrons both.