Electrons are arranged in energy levels. Levels are closer together the further away from the nucleus

Each energy level has sublevels called orbitals.

Orbitals

• s - 2 e's (spherical)
• P - 6 e's (infinity)
• d - 10 e's (fan)
• f - 14 e's (flower)

Aufbau principle (building up)

Pauli exclusion principle

Hund's Rule