Nuclear Chemistry and Radioactivity Unit 13 Notes

What is radioactivity? When the force that is holding the nucleus together is not strong enough to hold a very large nucleus together, it breaks up and causes a large release of energy. Elements 84 and up are radioactive.

There are 3 types of nuclear particles Alpha – two protons and two neutrons. **This can be stopped by a piece of paper. Beta – made of an electron. ** This can be stopped by a sheet of aluminum Gamma – electromagnetic radiation. **This can only be stopped by thick lead.

Half - Life The half life of any radioactive isotope is the amount of time it takes for half of the atoms to decay. This can be seconds or billions of years. EX: How many grams would remain after 4 half lives of an element if you begin with 30 grams? EX: An element has a half life of 12 years. How many grams would remain after 48 years if you started with 75 grams?

Measuring Radiation Film Badge Geiger counter (beta only) Scintillation counter Measured in roentgens FZcoI FZcoI

Fission VS. Fusion Nuclear fission splits a nucleus into pieces. This can cause a chain reaction of energy. Nuclear Fusion brings two nuclei together. This occurs in the sun as 2 Hydrogen atoms combine to form 1 Helium atom Both release large amounts of ENERGY!

Uses of Radiation Dating of organisms - carbon Cancer treatment  Cobalt 60 or Cesium 137 Biological testing and tracers - Iodine

Power plants and Bombs! Both use uranium for energy Power plants control a very slow reaction and use the heat for creating energy Bombs create a series of chain reactions

Alpha Decay Emits an alpha particle A Helium nucleus Symbol is either α or 4 2 He Original element loses 2 protons and 2 neutrons EX Ra  Rn He

Beta Decay Occurs in nuclei that have a high neutron to proton ratio Emits a beta particle, an electron Fast moving Symbol is 0 -1 β or 0 -1 e EX I  Xe β

Positron Emission (beta plus) Occurs in nuclei that have a low neutron to proton ratio Proton becomes a neutron + positron Fast moving Symbol is 0 1 β EX C  11 5 B β

Other forms of decay… Electron capture  Occurs in nuclei that have low neutron to proton ration  Proton + electron becomes a neutron  Emits X rays Gamma emission  High energy electromagnetic radiation  Extremely dangerous to human tissue

Examples of decay What would the alpha decay of Po result in?  4 2 He Pb What would the beta decay of Pb result in?  Tl