The half-life of carbon-14 is 5715 years. How long would it take for 100 grams to decay to 12.5 grams

We are given:

half-life of carbon = 5715 years

Initial mass = 100 grams

Final mass = 12.5 grams

Finding the time taken:

Number of half-lives:

We know that in the relation:

, n is the number of half-lives taken

replacing the given values:

12.5 / 100 = 1/2ⁿ

1/8 = 1/2ⁿ

2ⁿ = 8

2ⁿ = 2³

n = 3

Hence, it took 3 half-lives to reduce the mass to 12.5 grams

Number of years:

Time taken = 3 half-lives

we know that one half-life is 5715 years, replacing that value:

Time taken = 3*(5715) years

Time taken = 17145 years

Therefore, after 17145 years, a 100 gram sample of carbon will decay and only 12.5 grams will remain

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).

the answer is c. nacl