1. Warm-Up
An element that under goes beta decay will decay to another element with (a lower or a higher) atomic number
Which radiation has a negative charge associated with it?
Beta particles are stopped by (paper, aluminum, or lead)
If the number of protons equals the number of neutrons, the atom is (stable or unstable)
When Thorium (90 protons) ejects a beta particle, the nucleus left behind has _____ protons.

2. Radioactive Half life
The time needed for half of a radioactive sample to decay
Ex: The half life of Radium – 226 is 1620 years.
If you start with 100g of Radium-226, after 1620 years you will be left with 50g of Radium-226
How much will you be left with after 3240 years?
How much will you be left with after 4860 years?

3. Half life and fractions
How much of a substance do you have left after 1 half-life?
½ of it
How much of that same substance do you have left after 2 half lives?
¼ of it (half of a half)
How much of that same substance do you have left after 3 half lives?
1/8 of it (half of a quarter)

4. Half life and decayed matter
How much of a substance has decayed after 1 half-life
½ of it (there is only half left)
How much of that same substance has decayed after 2 half lives?
¾ of it (there is only ¼ left)
How much of that same substance has decayed after 3 half lives?
7/8 of it (there is only 1/8 left)