What are the four parts of an atom?

Structure of a beryllium atom: four protons, four neutrons and four electrons. Atoms are the basic units of matter and the defining structure of elements. The term "atom" comes from the Greek word for indivisible, because it was once thought that atoms were the smallest things in the universe and could not be divided.

proton, neutron, electron, nucleus are the main four.

But there are also electron cloud, quarks and sub orbitals.