1. The ELECTRON: Wave – Particle Duality
“No familiar conceptions can be woven around the electron. Something unknown is doing we don’t know what.”
-Sir Arthur Eddington
The Nature of the Physical World (1934)

2. The Dilemma of the Atom
Electrons outside the nucleus are attracted to the protons in the nucleus
Charged particles moving in curved paths lose energy
What keeps the atom from collapsing?

3. Wave-Particle Duality
JJ Thomson won the Nobel prize for describing the electron as a particle.
His son, George Thomson won the Nobel prize for describing the wave-like nature of the electron.
The electron is a particle!
The electron is an energy wave!

4. The Wave-like Electron
The electron propagates through space as an energy wave. To understand the atom, one must understand the behavior of electromagnetic waves.
Louis deBroglie

5. Electromagnetic radiation propagates through space as a wave moving at the speed of light.
c = speed of light, a constant (3.00 x 108 m/s)
 = frequency, in units of hertz (hz, sec-1)
 = wavelength, in meters

6. The energy (E ) of electromagnetic radiation is directly proportional to the frequency () of the radiation.
E = h
E = Energy, in units of Joules (kg·m2/s2)
h = Planck’s constant (6.626 x J·s)
 = frequency, in units of hertz (hz, sec-1)

7. Long Wavelength = Low Frequency Low ENERGY Short Wavelength =
Wavelength Table
Short
Wavelength =
High Frequency
High ENERGY

8. Answering the Dilemma of the Atom
Treat electrons as waves
As the electron moves toward the nucleus, the wavelength shortens
Shorter wavelength = higher energy
Higher energy = greater distance from the nucleus

9. The Electromagnetic Spectrum

10. Electron transitions involve jumps of definite amounts of energy.
This produces bands
of light with definite wavelengths.

11. Spectroscopic analysis of the hydrogen spectrum…
…produces a “bright line” spectrum

12. Flame Tests
Many elements give off characteristic light which can be used to help identify them.
strontium
sodium
lithium
potassium
copper

13. Electron Orbitals
Cartoon courtesy of lab-initio.com

14. The Bohr Model of the Atom
I pictured electrons orbiting the nucleus much like planets orbiting the sun.
But I was wrong! They’re more like bees around a hive.
Neils Bohr

15. Quantum Mechanical Model of the Atom
Mathematical laws can identify the regions outside of the nucleus where electrons are most likely to be found.
These laws are beyond the scope of this class…

16. Heisenberg Uncertainty Principle
“One cannot simultaneously determine both the position and momentum of an electron.”
You can find out where the electron is, but not where it is going.
OR…
You can find out where the electron is going, but not where it is!
Werner
Heisenberg

17. Electron Energy Level (Shell)
Generally symbolized by n, it denotes the probable distance of the electron from the nucleus. “n” is also known as the Principle Quantum number
Number of electrons that can fit in a shell:
2n2

18. Electron Orbitals
An orbital is a region within an energy level where there is a probability of finding an electron.
Orbital shapes are defined as the surface that contains 90% of the total electron probability.

19. s Orbital shape The s orbital has a spherical shape centered around
the origin of the three axes in space.

20. p orbital shape
There are three dumbbell-shaped p orbitals in each energy level above n = 1, each assigned to its own axis (x, y and z) in space.

21. d orbital shapes
Things get a bit more complicated with the five d orbitals that are found in the d sublevels beginning with n = 3. To remember the shapes, think of “double dumbells”
…and a “dumbell
with a donut”!

22. Shape of f orbitals

23. Energy Levels, Orbitals, Electrons
Orbital type
in the
energy level
(types = n)
Number of
orbitals
Electrons
electrons per
Energy level (2n2) 1 s 2 p 3 6 8 d 5 10 18 4 f 7 14 32

24. Orbital filling table

25. Electron Spin
Electron spin describes the behavior (direction of spin) of an electron within a magnetic field.
Possibilities for electron spin:

26. Pauli Exclusion Principle
Two electrons occupying the same orbital must have opposite spins
Wolfgang
Pauli

27. Electron configuration of the elements of the first three series

28. Element Configuration notation Orbital notation Noble gas
Lithium
1s22s1
____ ____ ____ ____ ____
1s s p
[He]2s1
Beryllium
1s22s2
[He]2s2
Boron
1s22s22p1
[He]2s2p1
Carbon
1s22s22p2
[He]2s2p2
Nitrogen
1s22s22p3
1s s p
[He]2s2p3
Oxygen
1s22s22p4
[He]2s2p4
Fluorine
1s22s22p5
[He]2s2p5
Neon
1s22s22p6
[He]2s2p6