1. CHAPTER 5
The Structure
of the Atom
5.2 The Quantum Atom

2. Why is the periodic table shaped this way?
We have seen in Chapter 2 that elements in the periodic table are organized by chemical properties.

3. Why is the periodic table shaped this way?
2 elements
8 elements
8 elements
18 elements
Why is it not shaped like a “box”?

4. Elements in the same column have similar chemical properties.
The periodic table
Li+
Na+ K+
They tend to donate 1 electron.

5. Elements in the same column have similar chemical properties.
The periodic table F–
Cl–
Br–
They tend to accept 1 electron.

6. Elements in the same column have similar chemical properties.
The periodic table
Never in
ionic
form
They do not donate or accept electrons.

7. Electrons are responsible for these chemical properties.
Elements in the same column have similar chemical properties.
Electrons are responsible for these chemical properties.
Quantum theory explains how the universe behaves on a very small scale.
Niels Bohr

8. A wave “particle” We intuitively think of light as a wave
and an electron as a particle

9. A wave “particle” But light waves come in bundles of light (photons)
and an electron behaves as a wave

10. frequency: the rate at which an oscillation repeats; one hertz (Hz) is a frequency of one oscillation per second.
wavelength: the distance (separation) between any two successive peaks (or valleys) of a wave.

11. The higher the frequency, the higher the energy

12. On the scale of atoms Planck’s constant (h) is used to calculate
Electrons
Light
Planck’s constant (h) is used to calculate
the energy and wavelength of electrons and photons

13. The sum of two waves can give a “bigger” wave.
Wave addition
The sum of two waves can give a “bigger” wave.

14. The sum of two waves can be zero!
Wave addition
The sum of two waves can be zero!

15. Wave addition Imagine a wave (wave 1) inside a box…
Wave 1 bounces off the wall and creates wave 2.
Could the waves cancel out each other?
Wave 1
Wave 2
Wave that “survives”

16. Perfect “fit”
Poor “fit”

17. The wavelength of the electron must be a “multiple” of the “size” of the atom.
Allowed
Not allowed

18. Only certain wavelengths are allowed…
… and wavelength is related to energy.

19. The Bohr model Energy is quantized!
Only certain energy levels are allowed
Energy is quantized!

20. Different quantum states can have the same wavelength
The Bohr model
Different quantum states can have the same wavelength

21. orbital: group of quantum states that have similar spatial shapes, labeled s, p, d, and f.

22. The orbital shapes are responsible for the shapes of molecules.

23. A look at history 460 – 370 BC 1808 1870 1897 1910 Today Democritus
Atomism
Dalton
“Modern”
atomic theory
Crookes
Cathode rays
Thomson
Discovery
of the electron
Rutherford
Discovery
of the nucleus

24. Wolfgang Pauli Quantum rule on electron structure
A look at history
460 – 370 BC
1808
1870
1897
1910
1925
Today
Democritus
Atomism
Dalton
“Modern”
atomic theory
Crookes
Cathode rays
Thomson
Discovery
of the electron
Rutherford
Discovery
of the nucleus
Wolfgang Pauli Quantum rule on electron structure
Pauli exclusion principle: two electrons in the same atom may never be in the same quantum state.

25. Quantum states can have the same energy level

26. Lithium’s 3rd electron has to go into the 2nd energy level
Fill lower-energy levels first
One electron per quantum state

28. Electrons are arranged in a pattern according to energy levels.
- Lower energy levels are filled first
- There can only be one electron per quantum state
Lithium’s 3rd electron has to go into the 2nd energy level
Energy is quantized