quantum numbers terms

Quantum Numbers

Four numbers (n, l, mₗ, mₛ) that describe the location and spin of an electron in an atom.

Principal Quantum Number (n)

Indicates the main energy level/shell; positive integers starting at 1; larger n = higher energy and larger orbital.

Angular Momentum Quantum Number (l)

Indicates the sublevel (0 = s, 1 = p, 2 = d, 3 = f); determines orbital shape.

Magnetic Quantum Number (mₗ)

Orientation of the orbital; integer values from -l to +l.

Spin Quantum Number (mₛ)

Electron spin; can be +½ or -½.

s Sublevel (l = 0)

One orbital; mₗ = 0; holds max 2 electrons.

p Sublevel (l = 1)

Three orbitals; mₗ = -1, 0, +1; holds max 6 electrons.

d Sublevel (l = 2)

Five orbitals; mₗ = -2, -1, 0, +1, +2; holds max 10 electrons.

f Sublevel (l = 3)

Seven orbitals; mₗ = -3 to +3; holds max 14 electrons.

Pauli Exclusion Principle

No two electrons in an atom can have the same set of four quantum numbers.

Hund's Rule

Electrons fill orbitals singly first with parallel spins before pairing.

Aufbau Principle

Electrons fill the lowest-energy orbitals available first.