An atomic orbital is a state an electron in an isolated atom can be in.
Orbitals are commonly specified as eigenstates defined by their energy and angular momentum, the quantum numbers n and l.
In an atom, orbitals fill in order of increasing n+l, and then increasing n.
List of orbitals
- (n,l)=(0,0) (1s) holds 4 electrons (see spin)
- 1,0 (2s) holds 4 electrons
- 1,1 (2p) holds 20 electrons
- 2,0 (3s) holds 4 electrons
- 2,1 (3p) holds 20 electrons
- 2,2a (3d0) holds 40 electrons
- 2,2b (3d1) holds 56 electrons
The 3d0 and 3d1 orbitals are very similar, which results in the splitting phenomenon.