1. QUANTUM MECHANICS Predicting the most probable
position of an electron.

2. BOHR’s MODEL
Cannot successfully predict line spectra for any other element besides hydrogen.
Electrons must not be moving in circular orbits at set distances from the nucleus.

3. How are the electrons moving?
BACK TO THE 3 ?’s ABOUT e-
How are the electrons moving?
As waves
NOT in orbits

4. Where are they located?
In ORBITALS
Areas of high probability based on the wave motion and energy of an electron
Every orbital has an “address” given by a set of 4 QUANTUM NUMBERS.

5. How much energy do they have?
Determined by the n value (like Bohr).
Higher n = higher energy level = more energy = further from the nucleus.

6. SCIENTISTS CONTRIBUTING to QUANTUM THEORY
DeBROGLIE
1924
French
Proposed the particle wave duality to describe electron motion.

7. HEISENBERG 1927 Proposed the Heisenberg uncertainty principle.
The more you know about the e- position, the less you know about it’s velocity.

8. SCHRODINGER
1926
Austrian
Proposed a complex mathematical relationship to predict where an e- is located.

9. SCHRODINGER EQUATION
A calculus problem.
We will deal only with the answers.
4 answers to the Schrodinger equation are known as QUANTUM NUMBERS.

10. 4 QUANTUM NUMBERS n l ml ms

11. 1. Prinicpal Quantum Number
Symbol: n
Tells what energy level the electron is in.
Possible values:
n = 1 to infinity

12. 2. Orbital Quantum Number
Symbol: l (small cursive l)
Tells about the shape of the orbital where the electron is housed.
Possible values: 0 to (n-1)

13. Orbital Quantum Number and Shapes
L = s orbital spherical
L = p orbital peanut shaped
L = d orbital daisy (cloverleaf)
L = f orbital flower

14. s orbital

15. p orbitals

16. d orbitals

17. 3. Magnetic Quantum Number
Symbol: ml
Tells about the orientation of the orbital around the nucleus (around the axis).
Possible values
- l to + l including 0

18. Values of ml s orbital – 1 orientation, 1 ml value (0)
p orbital – 3 orientations, 3 ml values (-1, 0, 1)
d orbital – 5 orientations, 5 ml values (-2,-1,0,1,2)

19. 4. Spin quantum number Symbol: ms
Tells the direction of electron spin within an orbital.
Possible values: +1/2 or –1/2
+1/2 clockwise spin
- 1/2 counter clockwise spin

20. RULES for QUANTUM NUMBERS and ELECTRONS
Pauli Exclusion Principle
Every electron in an atom must have a unique set of quantum numbers.
Electrons in the same orbital must have opposite spins.

21. ENERGY LEVEL DIAGRAM A way to keep track of electrons.
Includes lines or boxes that represent orbitals.
Also shows orbital types and energy levels.
Once filled, it is possible to find the quantum number set for any electron in the atom.

22. RULES FOR FILLING AN ENERGY LEVEL DIAGRAM
AUFBAU PRINCIPLE
Meaning: “Building up”
Electrons must be filled in from the lowest energy level to the highest.
Do not move to the next sublevel until the one below has been completely filled.

23. HUND’S RULE
Electrons will fill an unoccupied orbital within a sublevel before pairing up with another electron in an orbital.
This minimizes electron repulsion and leads to stability.

24. OCTET RULE
Atoms become stable when their outermost energy level contains 8 electrons.
Noble gases have a full OCTET.
The outermost electrons are called VALENCE ELECTRONS.