1. Scientists that changed our view of the atom
ATOMIC STRUCTURE
Scientists that changed our view of the atom

2. Democritus Did not conduct any experiments All matter is made of atoms
Atoms are indivisible and indestructible

3. John Dalton
John Dalton was born on September 6, 1766 in Cumbria, England.
He provided us with the first concrete ideas about the atom.

4. John Dalton – His Experiment

5. John Dalton Four points to his theory:
All matter is composed of atoms that are indestructible and indivisible
Atoms of one element are all the same; atoms of a different element are different (Au atoms are different from Ag atoms)
Atoms cannot be changed into different atoms by chemical of physical changes (Pb atoms cannot be turned into Au atoms)
All atoms are like Billiard Balls – a solid, sphere
Atoms react in whole numbers

6. JJ Thomson
Joseph John Thomson was born in Cheetham Hill, a suburb of Manchester on December 18, 1856.
He is given credit for the discovery of the electron.

7. JJ Thomson – His Experiment
Cathode Ray Tube

8. JJ Thomson – His Experiment

9. JJ Thomson * All gases had the same mass: charge ratio
3 Points to his theory
* All gases had the same mass: charge ratio
* All atoms contain small, charged particles called electrons
* The atom now looked like “Plum Pudding”

10. Goldstein
Eugene Goldstein was born in 1850 in Germany.

11. Goldstein – His Experiment
Cathode Ray Tube

12. Goldstein Major Point to his theory
He is given credit for the discovery of a positively charged particle = Proton
The atom was still thought to resemble Plum Pudding

13. Millikan
Robert Andrews Millikan was born on the 22nd of March, 1868, in Morrison, Ill. (U.S.A. )

14. Millikan – His Experiment
Oil Drop
Experiment

15. Millikan All electrons have the same mass
2 Points to his theory
All electrons have the same mass
About 1/2000 atomic mass unit
All electrons have the same charge
-1.6 x Coulomb
The atom was still thought to resemble Plum Pudding

16. Rutherford
Ernest Rutherford was born August 30, 1871 in Nelson, New Zealand (one of 12 children)

17. Rutherford – His Experiment

18. Rutherford 3 Points to his theory
* Most alpha particle went through = Atom is mostly empty space (area of electrons)
* Some alpha particles bounced straight back = atom has a solid mass (nucleus)
* Some alpha particles reflected = nucleus is positively charged
New Model = Nuclear Model

19. Schrödinger
Erwin Schrödinger born August 12 in Vienna, Austria in 1887.

20. Schrödinger – His Experiment

21. Schrödinger Major points Electrons do not follow fixed paths
They move randomly in areas of probability (orbitals)
There are specific energies associated with each orbital
New Model =
Quantum Mechanical Model

22. Chadwick
James Chadwick was born in Cheshire, England, on 20th October, 1891.

23. Chadwick – His Experiment

24. Chadwick
2 Points to his theory
Discovered the Neutron – Same mass as a proton, but without a charge
Mass could be converted into energy
Model was still thought to resemble the Quantum Mechanical Model