1. What does an atom look like?
How did scientists figure out what it looks like?
Truemper 2016

2. Atomic Theory
Truemper 2016

3. Democritus Smallest piece of all matter is not divisible
He named the smallest piece of matter “atomos,” meaning “not to be cut.”
Truemper 2016

4. Truemper 2016

5. John Dalton 1760-1844 Father of Modern Atomic Theory
matter is made of atoms
atoms in an element are identical
different elements have different atoms
atoms maintain their mass even in a chemical reaction
Truemper 2016

6. J.J. Thomson
1897
Truemper 2016

7. When a magnet was placed near the beam of light, it separated into two parts
Truemper 2016

8. When a magnet was placed near the beam of light, it separated into two parts
Truemper 2016

9. Thomson Model
Where did they come from?
This surprised Thomson, because the atoms of the gas were uncharged. Where had the negative charges come from?
Truemper 2016

10. Thomson Model
Proposed a model of the atom that is sometimes called the “Plum Pudding” model.
a sphere
with negatively charged electrons scattered.
Truemper 2016

11. J.J. Thomson 1897 Hear Thomson talk the Electron
discovered electrons (charged particles)
Truemper 2016

12. Truemper 2016

13. Rutherford 1911 Using atoms to see what is inside of other atoms
Truemper 2016

14. Rutherford
Truemper 2016

15. Rutherford Experiment Molecular Expressions
Truemper 2016

16. Rutherford’s experiment: Discovery of the Nucleus
Most of positively charged particles Rutherford shot at the gold foil passed right through without changing course at all.
However, some did bounce away from the gold sheet as if they had hit something solid.
He knew that positive charges repel positive charges.
Rutherford found the Nucleus
Truemper 2016

17. Rutherford’s model
A nucleus in the center, with electrons moving around in the open space
Truemper 2016

18. 1) Most of the volume of the atom is ...
empty space
Truemper 2016

19. 2) Virtually all mass atom found in ...
... the nucleus
Truemper 2016

20. 3) Strong, positive charge in the center of atom
                              
3) Strong, positive charge in the center of atom
Truemper 2016

21. Relative Sizes in the Atom
Truemper 2016

22. Did you know ... If the atom were the size of a football stadium, the nucleus would be the size of a....  
Truemper 2016

23.   .... a marble!!! 
Truemper 2016

24. Truemper 2016

25. Bohr Model
Electrons move in definite orbits around the positive nucleus
Like the planets orbiting the sun.
These orbits, or energy levels, are located at certain distances from the nucleus.
Truemper 2016

26. Truemper 2016

27. Chadwick discovers the nucleus has neutrons
Truemper 2016