The half-life of a strontium isotope is 25 years. How much of this particular isotope will remain after 100 years if the starting mass is 16 grams?

1 gram

Explanation:

Half life = 25 years

Starting mass = 16 grams

Time = 100 years

Number of half lives = Time / Duration of Half life = 100 / 25 = 4

After first Half life;

Remaining mass = 16 / 2 =  8 g

After Second Half life;

Remaining mass = 8 / 2 =  4 g

After Third Half life;

Remaining mass = 4 / 2 =  2 g

After Fourth Half life;

Remaining mass = 2 / 2 = 1 g

geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.