1. Atomic theory
Atoms:
The Building
Blocks of Matter

2. First, there was Democritus
Democritus was a Greek philosopher
“atomos”
He came up with the idea of the atom around 400BCE
He had no evidence, he just thought that that was just the way the world should work

3. Aristotle
Aristotle is the most famous and most influential of the Greek philosophers
He thought Democritus was
nuts!
Too bad for Democritus
And atomic theory

4. A brief history of the atom…
Democritus:
“atomos”
No experiments…not believed
Aristotle:
4 elements make up everything
Earth
Air
Fire
Water
4th century BCE
Ancient Greece

5. The word “atom” comes from a Greek word that means “unable to be cut”
… and you kept on cutting the leftover piece in half…
Imagine you had a piece of gold that you then cut in half…
…and then you cut one of these smaller pieces in half…
Gold Go ld

6. The word “atom” comes from a Greek word that means “unable to be cut”
…and kept going…
Eventually you would have 1 piece of gold left. If you cut it in half, you wouldn’t have gold any more – you’d have something else. This tiny, tiny single piece of gold is called an atom of gold. An atom is the smallest particle of an element that acts like the element.
…and kept going…
…and kept going…
An atom of gold

7. Hundreds of years later… Law of Conservation of Mass (1789)
Mass is neither created nor destroyed during chemical or physical reactions.
Antoine Lavoisier
Total mass of reactants =
Total mass of products

8. Soon after that… Early 1800’s England John Dalton Atomic Theory
All matter is made up of tiny, indivisible particles called atoms.
Atoms of the same element are identical – same physical and chemical properties
Atoms of different elements are different – different physical and chemical properties
Atoms can chemically combine in whole number ratios to form compounds and physically mix to form mixtures.
An atom cannot be changed into an atom of a different element by a chemical change – they may be combined, separated, or rearranged, but never created, destroyed, or changed.

9. A little after that…1897 JJ Thomson Cathode Ray Tube
Discovers the electron is negative

10. And a little after that…
Goldstein (1886)
Discovers canal rays (proton)
Milliken (1909)
Oil drop experiment finds the charge on an e-

11. Rutherford’s Gold Foil Experiment
And after all that…1911
Rutherford’s Gold Foil Experiment
start
experiment
DO NOT OPEN
RADIOACTIVE
MATERIAL
INSIDE + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
LOOK INSIDE
THE GOLD

12. And after all that… Ernest Rutherford Gold Foil Experiment
Discovers the Nucleus

13. Models of the Atom Thomson Model Dalton Model Blueberry Muffin e-
Solid Sphere
Thomson Model
Blueberry Muffin
blueberries = electrons
cake/muffin = positive matter e-
Positive material

14. Models of the atom Rutherford Model Dense, positive nucleus
Electrons revolving around nucleus in circular or elliptical orbits
Mostly empty space

15. Models of the atom Bohr Electrons are found in specific energy levels
Like planets around the sun

16. More on Models Electron Cloud or Quantum Mechanical Model
Electrons are in continuous motions and are shown as a probability cloud

17. Orbitals
Orbital- the area around the nucleus in which it is most likely to find an electron.
The come in a variety of shapes and sizes!!!
S P D F
Sphere peanut daisy/donut funkadelic

18. Check out this site for cool pics of orbitals!!!!!!!!!!
Orbital Shapes
1 type
3 types
5 types
7 types
Check out this site for cool pics of orbitals!!!!!!!!!!

19. Starting Electron Configurations
You have an address, so does an electron.
Most general = energy level (1, 2, 3, etc)
sub- level (s, p, d, or f)
degenerate orbital
Most specific = spin

20. Electron Configuration Rules
The Rules
Aufbau Principle- electrons fill lowest energy orbitals first.
Pauli Exclusion Principle- electrons will spread out into degenerate orbitals before pairing.
Hund’s Rule- electrons in the same orbital will have opposite spins (one up and one down)

21. The Diagonal Rule Tells the order of the energy of the orbitals
7s 7p 7d 7f
6s 6p 6d 6f
5s 5p 5d 5f
4s 4p 4d 4f
3s 3p 3d
2s 2p 1s

22. Configuration Diagrams
An electron is
represented by
an arrow
Only two arrows
per box
Place all up arrows
in first
Try to create some
Diagrams at this
Website

23. Electron Configurations
These are the same as the boxes, only they take up less space
Large # = energy level
Letter = orbital shape
superscript = how many electrons
Element # 19, Potassium:
1s22s22p63s23p64s1

24. Noble Gas Notation
Look for the noble gas that comes before the element you are trying to describe.
Write the noble gas symbol in brackets [ ]
Follow the symbol with the remaining orbitals that are necessary to account for all the electrons in the desired element.

25. The Electromagnetic Spectrum
Organizes light waves by energy, wavelength, and frequency

26. The photoelectric effect
Photon
a particle of light that contains a specific amount of energy (quantized)
The photoelectric effect
a photon of light hits and energizes an electron in an atom. This causes the electron to jump to a higher energy level. The electron inevitably falls back down to the lower energy level, and releases light.