An original sample of the radioisotope fluorine-21 had a mass of 80.0 milligrams. only 20.0 milligrams of this original sample remain unchanged after 8.32 seconds. what is the half-life of fluorine-21?
(1) 1.04 s (3) 4.16 s
(2) 2.08 s (4) 8.32 s

4.16s

Explanation:

N = 20*10⁻³g

N₀ = 80*10⁻³g

t = 8.32

N = N₀e⁻λt

In(N/N₀) = -λt

-λ = 1/t * In(N/N₀)

-λ = 1 / 8.32 * In (20*10⁻³ / 80*10⁻³)

-λ = 0.12 * In(0.25)

-λ = -0.167

λ = 0.167

t½ = 0.693 / λ

t½ = 0.693 / 0.167

t½ = 4.16s

thats how its supposed to be

hurricanes form when warm, moist air from the ocean surface quickly rises into the atmosphere and forms storm clouds and rain. when the clouds are formed, heat is released which warms the cool air in the upper regions of the atmosphere so that the cycle can continue. which two phases of the water cycle are repeated in this process?