- Quantum numbers are numbers used in Schrödinger’s equation to describe the orbital
size, shape, and orientation in space, and the spin of an electron. - The principal quantum number, n, describes the size of the orbital. It must be a positive
integer. It is sometimes referred to as the atom’s shell. - The angular momentum quantum number, l, defines the shape of the electron cloud.
If l=0, it is an s orbital; if l=1, it is a p orbital; if l=2, it is a d orbital; if l=3, it is an
f orbital, etc. - The magnetic quantum number, ml, describes the orientation of the orbital around the
nucleus. It can be integer values ranging from −lthrough 0 to +l. - The spin quantum number, ms, describes the spin of the electron and can only have
values of +^1 ⁄ 2 and −^1 ⁄ 2. - Be able to write the quantum numbers associated with the first 20 electrons.
146 STEP 4. Review the Knowledge You Need to Score High