1. Maximum Number of Electrons
the formula 2n2 is used to find the max. # of e- on any energy level.
- n = the energy level = (row on P.T.)
Ex…
energy level 3…
2(3)2 =
18 e-
energy level 6…
2(6)2 =
72 e-

2. Quantum numbers Principal Quantum Numbers
Map to determine location of the electrons…..
(Methods for denoting e- arrangement for an atom: orbital notation)

3. Quantum Numbers the ‘address’ of an e-.
there are four quantum numbers (actually letters)...
1st = n = energy level of the e-.
- ‘the principle quantum number’
- represented by rows on the periodic table
- 1 = lowest, 7 = highest
2nd = l = shape of sub-orbital
- 4 different shapes…found on each energy level
3rd = m = orientation of orbital in space.
- which axis the orbital lies on
4th = s = spin of the e- on its axis.
- clockwise or counter-clockwise

4. 1st Quantum Number
1. Principal Quantum Number (n) – Describes the size and energy of an orbital
↑n ↑E ↑Distance from nucleus & ↓stability
Ex. n=1

5. 2nd Quantum Number l = shape of orbital
there are four orbital shapes, represented by letters…
each orbital can only hold 2 e-.
s = sphere
= 1 orbital
= 2 total e-
- lowest energy
p = dumbbell
= 3 orbitals
= 6 total e-
d = clover-leaf
= 5 orbitals
= 10 total e-
f = double clover-leaf
= 7 orbitals
= 14 total e-
- highest energy

6. 2nd Quantum number cont.
2. Azmithual quantum number (l)- describes the subshell of the orbital
l = n – 1
if l = 0 then the electron is in the s subshell
l = 1 p subshell
l = 2 d subshell
l = 3 f subshell

7. 3rd Quantum number
3. Magnetic (ml) – describes the 3 dimensional orientation of an orbital
Values of ml = -l to +l
Ex. if l = 0 then ml = just one orbital
If l = 1 then ml = 3 orbitals (-1, 0, 1 = x, y, z)

8. Orbitals
‘s’ orbital
‘p’ orbitals

9. Orbitals
‘f’ orbitals
‘d’ orbitals

10. 4th Quantum number
4. Spin (ms) – describes the electron’s intrinsic magnetism
+ ½ (spin up) or – ½ (spin down)
each e- occupies the lowest energy orbital available

11. SPDF blocks in periodic table

12. Quantum Numbers - Practice
What are the 4 quantum numbers of:
The last electron in P
The 5th electron in Na
The 9th electron in Cl
The 5th electron in O
The last electron in Cu
The last electron in Fe