Question

The half-life of a radioactive element, such as carbon-14, is the time it takes for half of the atoms of

the element to decay. How many half-life periods bave passed if a fossil contains of the original
32 amount of carbon-14?
А. 3
B. 8
C. 5
D. 6

Answer 1

To determine the number of half-life periods that have passed, divide the initial amount by 2 repeatedly until you reach a value less than or equal to the given amount.

Step-by-step explanation:

Carbon-14 has a half-life of 5,730 years. To determine the number of half-life periods that have passed, divide the initial amount by 2 repeatedly until you reach a value less than or equal to the given amount.

In this case, the initial amount is 32 and we want to know how many half-life periods have passed when the amount is less than or equal to 16. The division process would be:

1. 32 ÷ 2 = 16
2. 16 ÷ 2 = 8
3. 8 ÷ 2 = 4
4. 4 ÷ 2 = 2
5. 2 ÷ 2 = 1

Therefore, 5 half-life periods have passed. The correct answer is C. 5.