1. Bohr model and Quantum Numbers
October 28, 2014

2. Bohr’s Model Why don’t the electrons fall into the nucleus?
Move like planets around the sun.
In circular orbits at different levels.
Amounts of energy separate one level from another.
When electrons are hit with energy (flame, heat) they jump to a different level.

3. Bohr’s Model
Nucleus
Nucleus
Electron
Electron
Orbit
Orbit
Energy Levels
Energy Levels

4. Bohr postulated that: Fixed energy related to the orbit
Electrons cannot exist between orbits
The higher the energy level, the further it is away from the nucleus
An atom with maximum number of electrons in the outermost orbital energy level is stable (unreactive)

5. } Fifth Fourth Increasing energy Third Second First
Further away from the nucleus means more energy.
There is no “in between” energy
Energy Levels n= 1,2,3,4,5,6,7
Fifth
Fourth
Third
Increasing energy
Second
First

6. How did he develop his theory?
He used mathematics to explain the visible spectrum of hydrogen gas

7. The line spectrum
electricity passed through a gaseous element emits light at a certain wavelength
Can be seen when passed through a prism
Every gas has a unique pattern (color)

8. Line spectrum of various elements
Helium
Carbon

9. The Quantum Mechanical Model
Energy is quantized. It comes in chunks.
A quantum is the amount of energy needed to move from one energy level to another.
Since the energy of an atom is never “in between” there must be a quantum leap in energy.
Schrödinger derived an equation that described the energy and position of the electrons in an atom

10. Atomic Orbitals
Principal Quantum Number (n) = the energy level of the electron.
Within each energy level the complex math of Schrödinger's equation describes several shapes.
These are called atomic orbitals
Regions where there is a high probability of finding an electron

11. Sublevels OF ENERGY s orbitals (sphere) p orbitals (dumbbell)
d orbitals (5 different shapes)
f orbitals (hard to visualize)

12. Sublevels, Orbital and number of electrons
SUBLEVEL NUMBER OF ORBITALS S p d f
To determine the number of electrons in a sublevel, we use the formula 2n2 where “n” energy level that is outside of the nucleus.

13. S orbitals 1 s orbital for every energy level 1s 2s 3s
Spherical shaped
Each s orbital can hold 2 electrons
Called the 1s, 2s, 3s, etc.. orbitals

14. P orbitals Start at the second energy level 3 different directions
3 different shapes
Each orbital can hold 2 electrons

15. The p Sublevel has 3 p orbitals

16. The D sublevel contains 5 D orbitals
The D sublevel starts in the 3rd energy level
5 different shapes (orbitals)
Each orbital can hold 2 electrons

17. The F sublevel has 7 F orbitals
The F sublevel starts in the fourth energy level
The F sublevel has seven different shapes (orbitals)
2 electrons per orbital

18. Summary
Starts at energy level

19. Electron Configurations
The way electrons are arranged in atoms.
Aufbau principle- electrons enter the lowest energy first.
This causes difficulties because of the overlap of orbitals of different energies.
Pauli Exclusion Principle- at most 2 electrons per orbital - different spins

20. Electron Configurations
First Energy Level
only s sublevel (1 s orbital)
only 2 electrons
1s2
Second Energy Level
s and p sublevels (s and p orbitals are available)
2 in s, 6 in p
2s22p6
8 total electrons

21. Third energy level
s, p, and d orbitals
2 in s, 6 in p, and 10 in d
3s23p63d10
18 total electrons
Fourth energy level
s,p,d, and f orbitals
2 in s, 6 in p, 10 in d, and 14 in f
4s24p64d104f14
32 total electrons

22. Great site to practice and instantly see results for electron configuration.