1. The Atomic Theory
The smallest particle of an element that can enter into chemical change.
2. Building block of all matter.
3. Consists of a central nucleus and electron orbitals outside the nucleus.

2. Nucleus
- Center of the atom
Contains protons & neutrons
Protons -
Neutrons -
Positively charged particle found in the nucleus.
Non-charged (neutral) particle found in the nucleus.
Electrons -
Negatively charged particle. Orbits the nucleus of an atom.
The mass of the atom is in the nucleus.
Proton = 1
Neutron = 1
Electron = 0