2 - Subatomic particles

Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in shells. 

• all atoms of a given element have the same number of protons. It is the atomic number of the element (you can know this number just looking at the periodic table).

An atom contains equal numbers of protons and electrons. Since protons and electrons have equal and opposite charges, this means that atoms are have no overall electrical charge.