Nuclear Chemistry

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!

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

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

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

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

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

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

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

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)