Answer:
93.33%
Explanation:
Thorium is a radioactive element with a molecular weight of 232g/mol. Thorium is very stable and can have 14.05 billion years of half-life period. Every half-life passed, the parent compound mass will be decayed by half. If the age of the rock is 1.4 billion years, then the amount of the parent compound will be:r = ½^(time elapsed/half-life)
r = ½^(1.4bil years/14.05 bil years)
r = ½^(0.0996)= 0.9333
r= 93.33%
The rock will have 93.33% of the parent compound and 6.67% of the decayed compound.
