What is inside of an atom?

atom. An atom is the smallest particle of an element that can still be defined as that element. The nucleus is the centre of an atom, containing protons and neutrons. Electrons are tiny, negatively charged particles that orbit the nucleus of an atom in energy levels (or shells). read more

For example, any atom with six protons in its nucleus is a carbon atom. Any atom with one proton is a hydrogen atom. 26 protons means iron, 92 protons for uranium, and so on. The number of neutrons in an atom can vary, but is typically close to the number of protons, for light elements (atoms with small numbers of protons). read more