Find the missing value for the radioactive isotope. (Round your answer to two decimal places.)

Question

Isotope	Half life (years)	Initial Quantity	Amount after 1000 Years
226Ra	1599	6 g	? g

Answer 1

This is an example of exponential decay.

m₀ = initial mass = 6 g

t = elapsed time in years

T = half life in years

m(t) = m₀ (0.5)^t/T

m(t) = 6 (0.5)^t/1599

Now plug in t = 1000 and get your answer in grams.