1. Atomic Theory

2. Atomic Theories Timeline
Use a graphic organizer like this to record information from this powerpoint and what you find online. You do NOT have to include Jabir nor al –Ghazali.
Name
Democritus
Dalton
Thomson
Etc.
Time Frame
Key Points
Candy
Model
Can you think of a candy that would be a good model for the atom according to this scientist?
You only need candy models for: Democritus, Dalton, Thomson, Rutherford, Bohr, and Schrodinger.

3. Earliest alchemists- 2500BC
The Egyptians were engaged in practical chemistry- metallurgy, making dyes, and producing glass. There is no reference to an atom.

4. Kanada- India, 600BC earliest recorded reference to the idea of an atom that I could find

5. Democritus 460 – 370 B.C.
There are various basic elements from which all matter is made
Everything is composed of small atoms moving in a void
Some atoms are round, pointy, oily, have hooks, etc. to account for their properties
Ideas rejected by leading philosophers because void = no existence

6. Simplified model- what doesn’t this show that makes his model distinct from Dalton’s?
Video

7. Jabir- Arabic chemist of 8th century
Considered one of the fathers of experimental chemistry but without atomisim

8. Al-Ghazali in the 11th Century revived Islamic science

9. Alchemy reigned in western Europe

10. John Dalton 1766-1844 Introduced his ideas in 1803
Each element is composed of extremely small particles called atoms
All the atoms of a given element are identical, but they differ from those of any other element
Atoms are neither created nor destroyed in any chemical reaction
A given compound always has the same relative numbers and kinds of atoms

11. Dalton’s Theory
1. Elements are made of tiny, indivisible particles (atoms).

12. Dalton’s Theory
2. An element’s atoms are identical and unique to that element.
C =
N =
Ni =
Note that real atoms are all basically the same shape and have no color.

13. Dalton’s Theory
3. Atoms combine chemically in simple whole-number ratios.
No half -atoms.

14. Dalton’s Theory
4. Chemical reactions occur when atoms separate, join, or rearrange. Atoms CANNOT be changed into another atom. (You can not make gold out of lead.) + + + +

15. Now go back and see if you can make a distinction between Dalton’s and Democritus’ models.

16. J.J. Thomson
Discovered electron 1897 – Cathode Ray Experiment
Plum Pudding model 1904
Electrons in a soup of positive charges
Discovered isotopes 1913

17. JJ Thomson’s Ideas

18. Experiments with Cathode Ray Tubes (late 1890s)

19. Cathode Ray Tube Experiment

20. Deflection of the “ray” Evidence of the electron
Video

21. Thomson’s plum pudding

22. A real plum pudding

23. The Electron The Proton
Goldstein CRT canal rays
Positive charge p+
Actual Mass: 1.67 x 10-24g
Relative mass: 1
J.J. Thomson CRT experiment
Negative Charge e-
Actual Mass: x 10-28g
Relative mass: 1/1840 the mass of proton (Millikan)

24. Ernest Rutherford 1871-1937 Nucleus Theory 1910
alpha particle gold foil experiment
An atom’s mass is mostly in the nucleus
The nucleus has a positive charge (Moseley)
Electrons in fixed orbit

25. Gold Foil Experiment (1909)
Video

26. Rutherford’s atom Nucleus with protons and “extra mass”

27. Classic atom model

28. James Chadwick 1891-1974 Worked with Rutherford
Interpreted work of the Curies
Discovered Neutron 1932
Nobel Prize in Physics 1935

29. Chadwick (1930) Evidence of the Neutron

30. The Neutron Chadwick 1932 - nuclear bombardment No charge n0
Actual Mass: 1.67 x 10-24g
Relative Mass: 1

31. Niels Bohr 1885-1962 Planetary Model 1913
Nucleus surrounded by orbiting electrons at different energy levels
Electrons have definite orbits
Utilized Planck’s Quantum Energy theory
Worked on the Manhattan Project (US atomic bomb)

32. Bohr’s atom with energy levels (1913)
Video

33. Bohr Model for Nitrogen
Pick A Candy!

34. Quantum mechanical model
Bohr’s model was good for hydrogen, but failed with atoms with more electrons
Schrodinger used new experimental results to come up with a mathematical equation that explains electron behavior
NO exact paths to follow- more of a cloud where electrons may be found
Video

35. Ernst Schrödinger 1887-1961 Werner Heisenberg 1901-1976
Quantum Mechanical Model 1926
Electrons are in probability zones called “orbitals”, not orbits and the location cannot be pinpointed
Electrons are particles and waves at the same time
Developed quantum numbers based on theories of Einstein and Planck

36. Schrodinger’s Model
Electron probability map.

37. Quantum Mechanical Theory Electron in a Hydrogen atom
Pick A Candy!

38. Add two other players to this timeline- Millikan and de Broglie
Add two other players to this timeline- Millikan and de Broglie. They are in your textbook.

39. Energy levels Electrons can only be at certain energy levels
Quantum- amount of energy needed to move from one energy level to the next
Cannot stop between levels

40. Energy levels Not evenly spaced
Higher energy levels are closer together.
Higher energy levels are found further from the nucleus.

41. Atomic orbitals
A region of space where there is a high probability of finding an electron
Defined mathematically by Schrodinger
Each orbital has a different shape

42. Orbital shapes s = spherical p= dumb bell on three axes
d= like a double p on three axes and an odd (one dumbbell with a donut)
S, p, and d are also the names of the sublevels

43. n = 2 orbitals

45. 3d orbital photo