Answer :
After 116 years, 125 g of strontium-90 would still be present.
Describe half-life.
A substance's half-life is the amount of time needed for half of a radioactive substance's original quantity to degrade. It is a phrase that is used in nuclear chemistry to describe how quickly unstable atoms radioactively decay into other nuclear species by emitting particles or the amount of time needed for the rate of radioactive material disintegrations per second to drop to half of what it was initially.
The number of half-lives needed to compute the mass of strontium-90 after 116 years is calculated as follows: 116/20=4 half-lives.
The mass of Sr-90 during the first half life is 2000/2=1000 g.
Sr-90's mass is 1000/2, or 500 g, during its second half life.
Sr-90 mass at its third half-life is 500/2, or 250 g.
Sr-90 mass equals 250/2=125 g at the fourth half-life.
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