1. Nuclear Chemistry

2. Henri Becquerel Accidently discovered a strange natural phenomenon
Sample of mineral called pitchblende placed on his desk next to a key (covered with photographic plate)
Created a picture of the key
– so pitchblende must be emitting something!

3. Radioactivity
The emanation coming from this substance is called radioactivity
some elements or isotopes spontaneously emit energetic particles
This is due to the degradation of their atomic nuclei

4. There are 3 different types of emanations or “rays” that come from radioactive substance
Alpha Particles
Beta Particles
Gamma Rays

5. Alpha Particles Large and move slowly
Easily blocked by a piece of paper, or skin
Mass #

6. Alpha Particles Identical with nuclei of helium atoms
Thus, they have 2 neutrons and 2 protons
Although they start with a charge of +2 (meaning they are missing 2 electrons) they quickly acquire 2 electrons.
This explains why they are commonly represented without a charge

7. Beta Particles
Are a stream of negatively charged electrons that move almost at the speed of light
They are fast!
Have a small mass so can penetrate further than alpha
Blocked by metals or protective clothing

8. Gamma Rays Photons (small packets) of electromagnetic energy
Best described as bundles of energy that are more energetic – thus more penetrating

9. Gamma Rays Move at the speed of light Penetrate very far!
Can be stopped (mostly) by thick lead or concrete
Gamma rays are neutral
Often occur simultaneously with alpha or beta emission

13. Radiation can be detected by a Geiger counter
A Geiger counter “clicks” when in the presence of radiation
It tells how much you are absorbing (gives a number in millirems)