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.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

the answer is   c.) 1575 j.

explanation: