Structure of an Atom
All matter is composed of atoms. An atom is composed of 3 types of sub-atomic particles:
1. Protons
2. Neutrons
3. Electrons
The protons and neutrons are present in the center of an atom, forming a small nucleus. The electrons orbit around the nucleus in shells or energy levels .
The simplified structure of a Lithium atom is shown below:

Atoms have no overall electrical charge, however the particles contain specific charge, listed below:
Protons --- Positive (+) charge
Neutron --- Neutral (0) no charge
Electron --- Negative (–)