1. QUANTUM MECHANICAL MODEL OF THE ATOM

2. DEFINITION OF TERMS QUANTUM – UNIT OF ENERGY
ORBITALS – space around a nucleus where the probability of finding an electron is greatest.
QUANTUM NUMBERS – set of four numbers used to describe the electron’s energy level in terms of:
a. distance from the nucleus
b. shape of the orbital
c. orientation in space (x, y, z)
d. direction of electron spin (clockwise, counter-clockwise)

3. ENERGY LEVELS OF THE ATOMIC ORBITALS
1. MAIN ENERGY LEVEL (MEL).
- represents the average distance of the electrons from the nucleus.
- values 1, 2, 3, 4, 5, 6 and 7

4. Electrons in MEL closer to the nucleus have the lowest energy

5. 2. SUBLEVELS or SUBSHELLS
- define the shapes of the orbitals
- has four possible shapes called
s, p, d and f
EACH SUBLEVEL HAS DIFFERENT NUMBERS OF ORBITALS AND EACH ORBITAL CAN ONLY HAVE A MAXIMUM OF 2 ELECTRONS

6. s p d f 1 orbital – 2 electrons 3 orbitals – 6 electrons

7. SUMMARY OF ENERGY LEVELS, ORBITALS AND ELECTRON RELATIONSHIPS
MEL (n)
MAXIMUM NUMBER OF ORBITALS (n2)
MAXIMUM NUMBER OF ELECTRONS PER ENERGY LEVEL (2n2) 1 2 4 8 3 9 18 16 32

8. ELECTRONIC CONFIGURATION
- Process of arranging the electrons around the nucleus
The problem?
The solution!

9. THE RESULT!!!

10. RULES GOVERNING ELECTRON CONFIGURATION
AUFBAU PRINCIPLE – electrons enter orbitals of lowest energy first.
PAULI’S EXCLUSION PRINCIPLE – only two electrons can occupy a single orbital.
HUND’S RULE OF MAXIMUM MULTIPLICITY– within the same sublevel, electrons prefer to occupy empty rather than half-filled orbitals.

11. What is the electron configuration of Oxygen?
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
Oxygen has 8 electrons.
Its electron configuration is:
1s 2 2s 2 2p 4
= 8 electrons

12. ELECTRON CONFIGURATION OF IONS
What is the electron configuration of S 2- ?
SOLUTION:
1. Solve for the total number of electrons.
e - = p+ - c
= 16 – (-2) = 18
2. Use the electron configuration chart
1s2 2s2 2p6 3s2 3p6
3. Check the number of electrons used.
= 18

13. √ √ EXCEPTIONS TO THE RULE 24Cr 1s2 2s2 2p6 3s2 3p6 4s2 3d4
29Cu 1s2 2s2 2p6 3s2 3p6 4s2 3d9
1s2 2s2 2p6 3s2 3p6 4s1 3d10 √ √