1. The Movers and Shakers of the Subatomic World.
Atomic Theory
The Movers and Shakers of the Subatomic World.

2. Dalton
In the early 1800’s, the English chemist John Dalton did a number of experiments that eventually led to the acceptance of the idea of atoms.

3. Dalton’s Atomic Theory
All elements are composed of atoms. Atoms are invisible and indestructible particles.

4. continued...
Atoms of the same element are exactly alike.
H H

5. continued...
Atoms of different elements are different.
O H

6. continued...
Compounds are formed by the joining of atoms of two or more elements.
H H O

7. Questions... What were the four parts of the Dalton’s atomic theory?
Say it again...

8. Was he right?
Dalton’s atomic theory of matter became one of the foundations of chemistry.
BUT it needed work…other scientists had to modify the theory.

9. Thomson
In 1897, the work of an English scientist J. J. Thomson provided the first hint that atoms were made up of even smaller particles
Atoms are divisible…Dalton was wrong!

10. Thomson’s Model
He stated that atoms are made up of positively (+) and negatively (-) charged particles

11. And...
He thought the positive (+) and negative (-) particles were s p r e a d o u t in atoms like p p u l d u d m i s n
(plums in puddin’)

13. Questions... What kind of particles did Thomson find in atoms?
What did his idea of an atom look like?

14. Was Thomson Right?
Not really…there are positively (+) and negatively (-) charged particles inside atoms.
BUT...

15. Rutherford’s Model In 1908, Rutherford discovered the nucleus.
He stated that atoms have a small, dense, positively (+) charged center called a nucleus.

17. Questions... What did Rutherford find inside the atom?
What did Rutherford’s atom look like?

18. So... Where are the negative particles (electrons)?
Particles are not spread out like plums in pudding…
Positive particles (protons) are in the center (nucleus).
Where are the negative particles (electrons)?

19. Bohr’s Model
In 1913, Niels Bohr proposed an improvement to Rutherford’s Model:
Electron’s move in definite orbits around the nucleus, like planets around the sun.

21. Questions... What did Bohr propose?
Where were the particles in Bohr’s model of an atom?
What did it look like?
What was special about the electrons in Bohr’s model?

22. Are we there yet?
Bohr’s model was used for a long time…
BUT...

23. Modern Atomic Model
An atom has a small, positively charged nucleus surrounded by a large region in which there are enough electrons (-) to make the atom neutral (0).

24. E E E E E P P P E P P P P P P P P P E E E E E E

25. Questions... Do electrons have specific orbits in the modern model?
What does the atom look like in the new model?

26. Make Your Timeline After the sheet is passed out:
write your name on it!
Fill out the timeline according to date, scientist, notes, and picture (if there is one) for each scientist we went over.
Neatness counts!!!!!
HAVE FUN