The isotope
Has a half-life of 7.5 seconds.If a sample contains 144 atoms of
,approximately how many such atoms were there present 30 seconds earlier?

Question

The isotope 
Has a half-life of 7.5 seconds.If a sample contains 144 atoms of 
,approximately how many such atoms were there present 30 seconds earlier?

Quizplus · Accepted Answer

Since the half-life of the isotope is 7.5 seconds, the number of remaining atoms after 7.5 seconds will be half of the original number. Similarly, after 15 seconds, it will be one-fourth of the original number, and after 30 seconds, it will be one-eighth of the original number.

So, if a sample contains 144 atoms of the isotope, then it means that 144 = (1/8) * N, where N is the original number of atoms present.

Solving for N, we get N = 1152.

Therefore, there were 1152 atoms of the isotope present 30 seconds earlier.

The Isotope Has a Half-Life of 7 ×\times× 108

The Isotope
Has a Half-Life of 7 $\times$ 10⁸