Quantum Numbers

Pauli Exclusion Principle: no two electrons can have the
same set of four quantum numbers

1st - Principle QN


2nd - Orbital QN


3rd - Magnetic QN


4th - Spin QN


n = 1,2,3...7

l goes from 0 to n-1 within an energy level

l values = 0 (for s) , 1(for p) , 2 (for d), 3 (for f) sublevels

Values of ml go from +l to - l , which gives 2l + 1 number of values

has 2 values:
+1/2 (spin up) and -1/2(spin down)

1. measures the average distance of the e- from the nucleus

1. indicates the shape of the orbital ( set of probable locations of the e- )

1. identifies the direction in e- orbital has around the nucleus

1. identifies the "spin" or rotation of the e- about its own axis

2. different values of n mean different energy levels

2. diff. values of l mean diff sublevels. In a sublevel all the e- have nearly the same energy.

2. specifies the e- orbital in which the e- is located within a sublevel.

2. shows that each orbital can contain only 2 e-

3. different values of n mean relatively large differences in the energies of the e-s

3. different sublevels within the same level may have moderately large differences in energy.

3. different values of ml mean little difference in energies of the e-

3. the direction of spin is either in one direction or the other

4. the smallest avgerage distance and the lowest energy occurs when n = 1; each increase in n increases those quantities.

4. within any level, the lowest energy sublevel is s, then p, then d, then f.

4. the number of possible values of ml within a sublevel idenities how many e- pairs that the sublevel can hold

4. when 2 e- (in an atom) have the same set of QN except for ms , then these e- are called an e- pair

5. the number of e- possible in a level is 2n2

5. the number of possible values of l for a level is equal to the value of n

5.these e- within an e- pair have essentially the same energy

Go to notes on Electronic Structure of the Atom

Send comments or questions to
Gwen Sibert
Roanoke Valley Governor's School