Quantum Numbers

•Four Quantum Numbers:

–Specify the “address” of each electron in an atom

–Used the wave equation to represent different energy states of the electrons

–Set of four #’s to represent the location of the outermost electron

Principal Quantum Number, n

This quantum number is the one on which the energy of an electron in an atom primarily depends. The smaller the value of n, the lower the energy level and the smaller the orbital.

The principal quantum number can have any positive value: 1, 2, 3, . . .

Orbitals with the same value for n are said to be in the same shell.

Energy Levels or Shells are sometimes designated by uppercase letters and related the principal quantum number as follows

Angular Momentum Quantum

 Number, l

This quantum number distinguishes orbitals of a given n

(shell) having different shapes.

It can have values from 0, 1, 2, 3, . . . to a maximum of (n – 

1).

For a given n, there will be n different values of l, or n 

types of subshells.

Orbitals with the same values for n and l are said to be in 

the same shell and subshell.