3b- Nuclear Half Life: Calculations

This is NOT the same radium isotope that was used in the UNDARK paint that the Radium girls used. That isotope is ²²⁶Ra, and it has a half life of 1600 years. That is why the graves of the dial painters still emit radiation and will continue to emit radiation for many many many years to come. 

If one half life is 11 days, how many half lives pass in the total time of 44 days?

• 3

• 4

• 11

• 44

How much radium-223 will remain after one half life?

• 120 g

• 223 g

• 240 g

• 60 g

How much radium-223 will remain after the second half life?

• 30 g

• 60 g

• 20 g

• 45 g

How much radium-223 will remain after the third half life?

• 15 g

• 40 g

• 5 g

• 10 g

How much radium-223 will exist after the 4th half life?

• 10 g

• 5 g

• 15 g

• 7.5 g

You will always start with 100%. Why?

• Because you start with the whole sample (before any has decayed)

• Because there are 100 pennies in a dollar

What percent of your sample will remain after the first half life?

• 100%

• 50%

• 75%

• 33%

What percent will be left after the 4th half life?

• 6.25%

• 12.5%

• 100%

• 50%

What fraction would you have left after the second half life?

• 1/2

• 1

• 1/8

• 1/4