Question

A sample of rock is found to contain 100 grams of a parent isotope. How many grams of the parent isotope will remain after one half-life?

Answer 1

The half-life of an isotope is the time taken for 50% of the isotope to decay, so after one half-life, half the original isotope is left.

Answer 2

50 grams of the parent isotope will remain after one half-life.

Step-by-step explanation:

Formula used to calculate remaining amount of an isotope after n half lives:

`A=(A_o)/(2^n)`

where,

A = Amount of isotope left after n-half lives

`A_o` = Initial amount of an isotope

n = number of half lives

Initial amount of an isotope =
`A_o`= 100 g

Number of half lives = 1

`A=(100 g)/(2^1)=50 g`

50 grams of the parent isotope will remain after one half-life.