1. Atomic Structure & Scientists
"Understanding means seeing that the same thing said different ways is the same thing." --- Ludwig Wittgenstein

2. Democritus of Abdera "Laughing Philosopher“ in the 4th century B.C.
Master Leucippus of Miletus & Democritus originated the atom concept.
There are five major points to their atomic idea.

3. Democritus Atomic Ideas
Point #1 - All matter is composed of atoms, which are bits of matter too small to be seen. These atoms CANNOT be further split into smaller portions.
Point #2 - There is a void, which is empty space between atoms.
Point #3 - Atoms are completely solid.
Point #4 - Atoms are homogeneous, with no internal structure.
Point #5 - Atoms are different in their size, shape, & weight.
Greeks thought he was crazy!!!! Democritus knew that atoms were indestructible units of matter, but he could not explain atoms chemical behavior.

4. The Father of the Chemical Atomic Theory
John Dalton ( )
The Father of the Chemical Atomic Theory
Teacher at the age of 12 years old
He wanted to expand upon Democritus’ theory
Dalton created several hypotheses & performed experiments
Created & published Dalton’s Atomic Theory

5. Dalton’s Atomic Theory
Matter is composed of small indivisible particles called atoms. The atom is the smallest unit of an element that enters into chemical combination.
An element is composed entirely of one type of atom. The properties of all the atoms of one element are identical and are different from those of any other element.
A compound contains atoms of two or more different elements. The relative number of atoms of each element in a particular compound is always the same. LAW OF DEFINITE PROPORTIONS
Atoms do no change their identities in chemical reactions. Chemical reactions simply change the way the atoms are joined together.

6. Dalton’s Atomic Model There it is! Dalton created this model in 1807.
Indivisible Spheres that are involved in chemical reactions.

7. Sir Joseph John Thomson
The man who chipped into the atom
On April 30, announced that cathode rays were negatively charged particles which he called 'corpuscles.'
"At first there were very few who believed in the existence of these bodies smaller than atoms. I was even told long afterwards by a distinguished physicist who had been present at my [1897] lecture at the Royal Institution that he thought I had been ”pulling their legs.' "
Corpuscles are now called electrons

8. J.J. Thomson

9. Cathode Ray Tube
The two plates about midway in the CRT were connected to a powerful electric battery thereby creating a strong electrical field through which the cathode rays passed. Thomson also could use magnets, which were placed on either side of the straight portion of the tube just to the right of the electrical plates. This allowed him to use either electrical or magnetic or a combination of both to cause the cathode ray to bend.

10. Plum Pudding Atomic Model
1904 article: “We suppose that the atom consists of a number of corpuscles moving about in a sphere of uniform positive electrification” .
“Plum Pudding model," where the pudding represents the sphere of positive electricity and the bits of plum scattered in the pudding are the electrons.

11. Eugen Goldstein ( )
1886, the German scientist observed "canal rays" flowing in the opposite direction  through a cathode ray tube by putting holes or canals in the cathode. 
From this discovery the idea was built that there is a unit of positive charge in the atom referred to later as the proton. 
Why don’t I have a picture? Can’t find one!!! Who stole his thunder?

12. Ernest Rutherford (1871-1937) The New Zealand radioactive scientist
Worked with Sir J.J. Thomson
He was fun, outgoing and vigorous, the life of the party -- a great, big, over-grown child. He was also a hard-working scientist who loved science for itself and never tired of playing in the laboratory.

14. Gold Foil Experiment

15. Rutherford’s Accomplishments
For the purposes of his 1911 paper, he considered the nucleus to act as a point:
"We shall suppose that for distances less that 10¯12 cm the central charge and also the charge on the alpha particle may be supposed to be concentrated at a point." Rutherford never used the word "nucleus" in his paper. His phrase was "charge concentration.“
We connect him with the discovery of the nucleus
He furthered concluded that atom is primarily empty space with a negative region surrounding the dense core.
Renamed “canal rays” to protons in 1920 after his work with the nucleus.

16. Sir James Chadwick ( )
Accidentally found himself in the line for those hoping to major in physics.
Trapped in Germany when WW I broke out, Chadwick was imprisoned in a horse stall at a racetrack that served as an internment camp
Worked with Rutherford
In 1932, Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons
                                           

17. Sir James Chadwick All elements except hydrogen contain neutrons
Chadwick paved the way towards the fission of uranium 235 and towards the creation of the atomic bomb.
Time Magazine declared the discovery of the neutron as one of the 100 Most Important Milestones of the 20th century.
Helped with the Nuclear Atomic Model

18. Nuclear Atomic Model

19. Robert Millikan (1868-1953) Taught himself physics!
In 1909, he began experiments to determine the electric charge of a single electron in Chicago.
In 1916, he proved Einstein’s theory of the photoelectric effect.

20. Oil Drop Experiment Determined the mass and charge of the electron
Charge = 1.60 x10-19 C
Mass= 9.11 x10-28 g

21. Subatomic Particle Summary
Symbol
Electrical Charge
Actual Mass
When Discovered
PROTON p+ +1
1.67 x10-24 g
1886
ELECTRON e- -1
9.11 x10-28 g
1897
NEUTRON n
1932

22. Nobel Prize Winners Sir J.J. Thomson (1906) Ernest Rutherford (1908)
Robert Millikan (1923)
Sir James Chadwick (1935)