1. Quantum Theory and The Atom

2. Objectives Compare the Bohr and quantum mechanical models of the atom
Predict the positions of electrons in an atom using the concepts of quantum numbers and orbitals
Identify the relationships among a hydrogen atom’s energy levels, sublevels, and atomic orbitals

3. Bohr Models

4. Bohr Model Hydrogen atom has only certain allowable energy states
Lowest state = ground state
Atom gains energy = excited state
Even though H has only 1 electron, it can be in many different excited states
When atom gains energy, electrons orbit further from the nucleus….energy levels
The higher the energy level, the further from the nucleus the electron orbits

5. Bohr Model of the Atom
Let’s look at hydrogen atom

7. Electron Configuration
Aufbau principle – electrons occupy the lowest energy orbital available
Pauli Exclusion principle – max of two electrons may occupy an orbital
Hund’s Rule – single electrons with same spin must occupy each orbital before electrons with opposite spin can occupy that orbital.

9. Explain Bright Line Spectrum
You must be able to explain why atoms emit bright line spectrums
Read page 128 in book
Let’s do stair step model/demo again

10. Quantum Mechanical Model
French scientist Louis de Broglie accounted for fixed energy levels in Bohr’s model
Quantized electron orbitals had characteristics similar to a wave

11. Standing Wave

12. Atomic Orbitals
A 3-dimentional region around the nucleus that describes an electron’s probable location
Orbital: The region in space where there is a probablility of finding an electron
Predicted by de Broglie’s wave function
Λ = h/mv
Where λ = wavelength, m = mass of particle, v = velocity of particle, h = Planck’s constant

15. Subsequent orbitals are just bigger: the electrons are located further from the nucleus because they contain more energy

17. P Orbital

18. d orbital

19. Quantum Numbers
If an atom absorbs energy from its ground state, it can be found in the 2nd, 3rd, 4th, etc. energy levels.
1st energy level, n = 1
2nd energy level, n = 2
Etc…
“n” is the principle quantum number

20. 1st Energy Level
Only one orbital for 1st energy level…. The S orbital

21. 2nd Energy Level Two orbitals…S and P
S orbital is larger than 1st energy level

22. Remember
An orbital is a description of an electron wave (remember the standing wave)…describes the probability of an electron being located in a certain space
Also describes where we will NOT find an electron (remember the node of a standing wave)

23. 3rd Energy Level Has S, P, and D orbitals 4th Energy Level
Contains F orbital (seen only for inner transition elements)

24. Homework
5.2 assessment P