1. History of the Atom Bellringer: K: Write what you know about atoms
W: write what you want to know about atoms
Objective:
SWBAT explain how the modern model of the atom has evolved

2. Table Set Up
Date
Person
Idea/Discovery
Keyword(s)

3. (greek for indivisible)
HISTORY OF THE ATOM
Democritus develops the idea of atoms
460 BC
He pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called:
ATOMA
(greek for indivisible)

4. HISTORY OF THE ATOM ATOMS John Dalton 1808
Suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity (they can bounce forever and never slow down) and called them
ATOMS

5. HISTORY OF THE ATOM
1808
John Dalton
All elements are composed (made up) of atoms. It is impossible to divide or destroy an atom.
All atoms of the same elements are alike. (One atom of oxygen is the same as another atom of oxygen.)

6. HISTORY OF THE ATOM
1808
John Dalton
Atoms of different elements are different. (An atom of oxygen is different from an atom of hydrogen.)
Atoms of different elements combine to form a compound.

7. HISTORY OF THE ATOM ELECTRON
Joseph John Thompson
1898
found that atoms could sometimes eject a far smaller negative particle which he called an
ELECTRON

8. HISTORY OF THE ATOM PLUM PUDDING MODEL 1904
Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge like plums surrounded by pudding.
PLUM PUDDING MODEL

9. HISTORY OF THE ATOM Ernest Rutherford
1910
Supervised Geiger and Marsden carrying out his famous experiment.
They fired Helium nuclei at a piece of gold foil which was only a few atoms thick.
they found that although most of them passed through. About 1 in 10,000 hit

10. HISTORY OF THE ATOM
gold foil
helium nuclei
helium nuclei
They found that while most of the helium nuclei passed through the foil, a small number were deflected and, to their surprise, some helium nuclei bounced straight back.

11. HISTORY OF THE ATOM
Rutherford’s new evidence allowed him to propose a more detailed model with a central nucleus.
He suggested that the positive charge was all in a central nucleus. This held the electrons in place by electrical attraction.
He also suggested that atoms were mostly empty space.
However, this was not the end of the story.

12. HISTORY OF THE ATOM 1913 Niels Bohr
Studied under Rutherford at the Victoria University in Manchester.
Bohr refined Rutherford's idea by adding that the electrons were in orbits. Rather like planets orbiting the sun, with each orbit only able to contain a set number of electrons.

13. Bohr’s Atom
electrons in orbits
nucleus

14. History of the Atom 1932 James Chadwick neutron
Discovered a neutrally charged particle located in the nucleus of an atom.
This new particle has the same mass as a proton.
He called this particle a
neutron

15. History of the atom 1962 Erwin Schrödinger Quantum Mechanical Model
“Electron Cloud”
Refers to a region outside the nucleus where the electron is most likely to be found
Because we cannot know exactly where an electron is at any given time, we use the model to predict the places where it probably is. (This idea is based on quantum mechanics and Heisenberg’s uncertainty principle)*

17. Bohr Model vs. Electron Cloud

18. HELIUM ATOM
Shell
proton N + - + N -
neutron
electron

19. ATOMIC STRUCTURE
Particle
Charge
proton
+ charge
neutron
No charge
electron
- charge

20. Atomic Timeline Activity

21. Activity Create a timeline of the evolution of the atomic model.
Include all major events from Democritus to the present.
Each event needs:
The year
The person responsible
A short description of the new idea
An illustration of what people thought the atom looked like at that time.

22. Expectations
Working quietly- silent or whispering to your neighbor (level 1)
Raise your hand for help
Working productively and independently
You can get up for more supplies, but not to socialize
You will need to turn this in at the end of class, so you need to work effectively without wasting time.