1. Aim: How can we describe the structure of an atom?
Do Now:
Take out a calculator and reference tables.
Write a brief description about what you know about the atom.

2. Timeline of Atomic Models
- Greek era- matter is composed of wind, earth, water, and fire ’s - Robert Boyle identifies gold and silver as elemental (not made of earth, wind, fire, or earth).

3. Timeline of Atomic Models
1803 – Dalton’s theory of the atom can be summarized as the following:
All elements are composed of indivisible atoms.
All atoms of a given element are identical.
Atoms of different elements are different (have different masses).
Compounds are formed by combinations of different elements.
Cannonball model

4. Timeline of Atomic Models 1897 - Thompson
Uses a cathode ray tube to show that particles can be deflected towards positive ends by an electrical or magnetic field.
Because the only source for the particles was the atoms present, he theorized that atoms must have negatively charged particles called electrons.
Plum Pudding Model

5. Timeline of Atomic Models 1909 – Rutherford’s Gold Foil Experiment
Directed alpha particles (+ charged) through a very thin sheet of gold.
Some of the alpha particles were deflected (which would not happen if the plum pudding model were correct) and some bounced back completely.
Rutherford concludes that atoms have a dense central positively charged core called the nucleus and the remainder of the atom is essentially empty space.
Also determines that there must be negatively charged particles outside the nucleus.

6. Rutherford’s experiment

7. Rutherford’s Model of an Atom

8. Timeline of Atomic Models 1913 - Bohr
Developed the planetary model of the atom.
Shows a center (nucleus), and rings (called shells) of orbiting electrons.

9. Timeline of Atomic Models The Wave Mechanical Model
Treats electrons as a wave and a particle instead of just a particle.
Instead of moving in fixed shells, the electrons move in areas called orbitals.
Each electron has a definite amount of energy.
Placement of electrons can be predicted but not defined.
The nucleus is still dense and positively charged.

10. Parts of the Atom
Proton
Neutron
Electron
Charge
Location

11. Activity

12. Homework #
Review Book pages 5 and 6. Answer #1 -12.