If 140. mg of fluorine-18 is shipped at 8: 00 a. m., how many milligrams of the radioisotope are still active when the sample arrives at the radiology laboratory at 1: 30 p. m.

To answer the question we need to know the half-life of fluorine for reference we have chlorine half-life as 110. The fraction of chlorine remaining would be given by

Explanation:

Here we know and is known as the number of Half-life that have elapsed during this process  Now we are giving the time of start as 8 a.m. and time of finishing at 1:30 p.m., so the time between is 5 ½  hours. Which on converting in minutes will give 330 minutes.

So Half Life elapsed would be given by =

Hence the amount remaining would be =

17.4 mg of the radioisotope are still active when the sample arrives at the radiology laboratory at 1:30 P.M.

Explanation:

Half-life of F-18 is found to be 109.7 minutes

Rate constant      

t = time taken = 5 hours 30 minutes = 330 minutes

[A] is the final quantity  

 is the initial quantity

Plugging the values and solving for [A]

[A] = 17.4mg is the Answer

it means there are 3 atoms of oxygen