# An original sample of a radioisotope had a mass of 10 grams. After 2 days, 5 grams of the radioisotope remains unchanged. What is the half life of the radioisotope?

$2$ days
Sample was initially $\text{10 g}$. After $2$ days it’s decreased to $\text{5 g}$. Therefore, half life of sample is $2$ days.