What occupies the energy levels of an atom?

Electrons occupy the energy levels of an atom. The energy level of an atom exists in the electron cloud that surrounds the nucleus. The nucleus is home to the protons and neutrons of the atom.

Electrons are negatively charged. This negative charge balances out the positive charge of the protons in the nucleus of the atom.

Electrons move at a high speed, making it hard to pinpoint their exact location. The electrons are organized in shells at a specific distance away from the nucleus.

The higher the atomic number of an element is, the more electrons it has; therefore, those with higher atomic numbers have more shells and are larger.