Atomic Orbitals

Starting with the energy level/shell closest to the nucleus electrons fill the different shells in order of increasing energy.

Shell 1	Shell 2	Shell 3	Shell 4
——————————- Increasing Energy —————————–>

Energy levels or shells can be divided into sub-shells, which can hold different numbers of electrons.

	Shell 1	Shell 2		Shell 3			Shell 4
Sub-Shell	s	s	p	s	p	d	s	p	d	f

Within each sub-shell there are one or more orbitals. Each orbital can hold a maximum of two electrons (of opposite spin).

	Shell 1	Shell 2		Shell 3			Shell 4
Sub-Shell	s	s	p	s	p	d	s	p	d	f
Number of orbitals in sub-shell	1	1	3	1	3	5	1	3	5	7
Number of electrons allowed in each orbital	2	2	2	2	2	2	2	2	2	2
Total number of electrons in each sub-shell	2	2	6	2	6	10	2	6	10	14

s-orbitals | p-orbitals | d-orbitals