Asample 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?

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

Explanation:

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

where,

A = Amount of isotope left after n-half lives

= Initial amount of an isotope

n = number of half lives

Initial amount of an isotope == 100 g

Number of half lives = 1

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

a.) is the correct answer.

explanation: