1. Quantum Theory and the Atom
Section 5-2
Quantum Theory and the Atom

2. Objectives Compare the Bohr and quantum mechanical models of the atom
Explain the impact of de Broglie’s wave-particle duality and the Heisenberg uncertainty principle on the modern view of electrons in atoms
Identify the relationships among a hydrogen atom’s energy levels, sublevels, and atomic orbitals

3. Bohr (1913) Proposed the quantum model for H
Based on Planck/ Einstein’s quanta energy
H atom has only certain allowable energy states
Lowest = ground state
Gaining energy = excited state

4. Continued 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. De Broglie (1924)
Electrons, like light, have particle-wave dual nature
Only multiples of 1/2 wavelengths allowed in circular orbits

8. 1 half-wavelength
2 half-wavelengths
3 half-wavelengths

9. Continued All moving particles behave like waves
Wave characteristics decrease as mass increases

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

11. Schrödinger (1926)
Quantum mechanical model
Limited electrons to only certain energy levels

12. Quantum Mechanical Model
Principal quantum numbers (n)
n = number of principle energy levels
Lowest level= ground state= n= 1
Inside of principle energy levels are sublevels
s, p, d, f
Inside sublevels are orbitals
s has 1, p has 3, d has 5, f has 7
Inside each orbital are 2 electrons

13. s orbital

14. Three p orbitals

15. Five d orbitals

16. Seven f orbitals

17. Look at Table 5-2 (p. 134)