Electronic configuration

• Hund's rule states that electrons will occupy the orbitals singly before pairing takes place
• an orbital is a region within an atom that can hold up to two electrons with opposite spins
• a quantum shell defines the energy level of an electron
• the Pauli exclusion principle states that two electrons cannot occupy the same orbital unless they have opposite spins
• s hold up to 2 electrons
• p holds up to 6 electrons
• d holds up to 10 electrons
• f holds up to 14 electrons
• 1s - 2s - 2p - 3s - 3p - 4s - 3d - 4p - 5s - 4d - 5p - 6s - 5d - 6p
• s orbitals are spherical
• p orbitals have a dumbbell shape
• 3d is sometimes filled before 4s as if it is filled or half filled, it would be more energetically stable
• the s block consists of elements in groups 1 and 2
• the p block consists of elements in groups 3 - 8
• the d block consists of the transition metals