1. The Bohr Model, Wave Model, and Quantum Model
Sections
The Bohr Model, Wave Model, and Quantum Model

2. Objectives Draw Bohr Models Describe the wave behavior of matter
Arrange electrons in an atom
Identify energy levels
Apply Heisenberg’s Uncertainty Principle
Describe the quantum mechanical model

3. Key Terms Ground state Excited states Matter waves momentum
Uncertainty principle
Wave functions
Probability density
Electron density
Orbitals
Electron shell
subshell

4. Bohr Model of the Atom
In 1913 Niels Bohr proposed quantum model for the H atom
Bohr proposed H atom has only certain allowable energy states
Lowest state= ground state
Gaining energy = excited state

5. Bohr Model of the Atom
Electrons move in certain, specific, circular orbitals
Smaller orbit = lower energy level
Assigned the allowable electron orbitals the principle quantum number, n.
1st orbit= lowest energy: n=1
2nd orbit= 2nd lowest energy: n=2

6. Bohr Model of the Atom
Energy is added to an atomelectron moves to higher energy level
Electron in “excited state” drops to a lower energy orbit emits a photon
E = E higher-energy orbit – E lower-energy orbit= E photon= h

8. Bohr Model of the Atom Problems with Bohr’s model Only explained H
Did not explain why electrons should only be allowed certain, specific energy levels

9. De Broglie
1924
Electrons, like light also had a particle-wave dual nature
Only multiples of half wavelengths are allowed in circular orbits

11. 1 half-wavelength
2 half-wavelengths
3 half-wavelengths

12. De Broglie
Formulated an equation for the wavelength, mass, and velocity of a particle

13. Heisenberg Uncertainty Principle
Fundamentally impossible to know precisely both the velocity AND position of a particle at the same time.
Cannot measure an object without disturbing it

14. Quantum Mechanical Model
1926
Schrödinger
Limited electrons to only certain energy levels
Atomic orbital: 3 dimensional area around the nucleus that predicts the 90 % PROBABLE location of an electron

15. Electron Density Diagram

16. Quantum Mechanical Model
Assigns principal quantum numbers (n) relative to sizes and energies of orbitals
(n) specifies atom’s major energy levels= principle energy levels
Lowest level= ground state= n= 1
H has 7 energy levels, n= 1 to 7

17. Quantum Mechanical Model
Principal energy levels contain energy sublevels
Principal energy level 1 has 1 sublevel
Principal energy level 2 has 2 sublevels
Principal energy level 3 has 3 sublevels

18. Energy Sublevels s, p, d, and f
Labeled according to shapes of orbitals
s = spherical
p = dumbbell
d and f = not all have same shape

19. s and p orbitals

20. Three p orbitals

21. d orbitals

22. Energy Sublevels Each orbital contains 2 electron at most
Principal energy level 1 has 1 sublevel: 1s orbital
Principal energy level 2 has 2 sublevels: 2s and 2p
2p sublevel has 3 dumbbell-shaped p orbitals (2px, 2py, and 2pz)
Principal energy level 3 has 3 sublevels: 3s, 3p, and 3d
d sublevels have 5 orbitals
Principal energy level 4 has 4 sublevels: 4s, 4p, 4d, and 4f
f sublevels have 7 orbitals