Calcium-47, used to evaluated bone metabolism, has a half-life of 4.5days: how many milligrams of a 16mg sample of calcium-47 remain after 18 days?

For this problem, we use the formula for radioactive decay which is expressed as follows:

An = Aoe^-kt

where An is the amount left after time t, Ao is the initial amount and k is a constant. 

We calculate as follows:

An = Aoe^-kt
0.5 = e^-k(4.5)
k = 0.1540

An = Aoe^-kt
An = 16e^-0.1540(18)
An = 1.00 mg

Hope this answers the question. Have a nice day.

if two electrons have the same n, the same ℓ, and the same ml, then they are in the same orbital. the pauli exclusion principle states that no two identical fermions (a fancy word for electrons and other subatomic particles like electrons) may occupy the same quantum state in an atom simultaneously.