More Half-Lives Help

  1. A common nuclear byproduct is cesium-137. For example, it was found in the aftermath of the problems at the Fukushima nuclear reactor site in Japan. Cesium-137 undergoes beta–decay to form an isotope of barium which is largely stable. Scientists have measured the following data about the decay of cesium-137. Find the pattern and fill in the missing data:

N(t)
Mass of the atoms that haven’t decayed yet / T
(Time, in years)
100g / 0
50g / 30
60
12.5g
6.25g / 120
  1. Half-life is the time it takes for ½ of something to decay. What is the half-life for cesium-137?
  2. Does the half-life change depending on how much is left? How many years does it take for half of the cesium-137 to decay when there is:

100g of cesium25g of cesium12.5g of cesium

  1. Plutonium-239, an isotope often created in nuclear reactors, has a half-life of 24,000 years. If you begin with 50g of plutonium-239...
  2. How long will it be until you have only 12.5 g?
  3. How long will it be until you have only ~6 g?

More Half-Lives Help – ANSWER KEY

  1. A common nuclear byproduct is cesium-137. For example, it was found in the aftermath of the problems at the Fukushima nuclear reactor site in Japan. Cesium-137 undergoes beta–decay to form an isotope of barium which is largely stable. Scientists have measured the following data about the decay of cesium-137. Find the pattern and fill in the missing data:

N(t)
Mass of the atoms that haven’t decayed yet / T
(Time, in years)
100g / 0
50g / 30
25g / 60
12.5g / 90
6.25g / 120
3.125g / 150
  1. Half-life is the time it takes for ½ of something to decay. What is the half-life for cesium-137?30 years
  2. Does the half-life change depending on how much is left? How many years does it take for half of the cesium-137 to decay when there is:

100g of cesium – 30 years25g of cesium – 30 years12.5g of cesium– 30 years

  1. Plutonium-239, an isotope often created in nuclear reactors, has a half-life of 24,000 years. If you begin with 50g of plutonium-239...
  2. How long will it be until you have only 12.5 g? 502512.5 so 48,000 years
  3. How long will it be until you have only ~6 g? 502512.56.25 so 72,000 years