Question

the half-life of the radioactive element unobtanium-53 is 5 seconds. if 80 grams of unobtanium-53 are initially present, how many grams are present after 5 seconds? 10 seconds? 15 seconds? 20 seconds? 25 seconds?
the amount left after 5 seconds is \boxed{} grams.

Explanation:

Step1: Recall half - life concept

The half - life of a radioactive substance is the time it takes for half of the substance to decay. So, after one half - life period, the amount of the substance remaining is half of the initial amount.
The initial amount \(A_0 = 80\) grams and the half - life \(t_{1/2}=5\) seconds. After \(t = 5\) seconds (which is one half - life), the amount remaining \(A\) is given by \(A=\frac{A_0}{2}\).

Step2: Calculate the amount after 5 seconds

Substitute \(A_0 = 80\) into the formula \(A=\frac{A_0}{2}\). So, \(A=\frac{80}{2}=40\).

Answer:

40