Question

4. Which of the following naturally occurring radioisotopes would be most useful in dating objects thought to be millions of years old? (1 point) a. carbon14; t1/2= 5.73 x 103 years b. potassium40; t1/2= 1.28 x 109 years c.thorium234; t1/2= 25 days d.radon222; t1/2= 3.8 days

Answer 1

The answer to this question is going to be answer choice b.
Potassium-40;t1/2=1.28 x 110^9

Answer 2

potassium-40

t₁/₂= 1.28 x 10⁹ years

Step-by-step explanation:

As we have to use the radioactive isotope for determination of age of something millions years old, we have to take an isotope which has half life more than millions years. With that kind of isotope only we can determine the age as only that isotope would left after million years atleast.

The carbon-14 has half life of only 5730 years (which is some thousands only) and the half life of chromium and radon is only in days.

So we have to use potassium-40.