Question

A radioactive isotope has a half-life of 2 hours. If a sample of the element contains 600,000 radioactive nuclei at 12 noon, how many radioactive nuclei would be left at 6pm? PLEASE HELP ASAP

Answer 1

75,000 nuclei

Step-by-step explanation:

The half life of a radioactive substance is the time taken for half he original mass of that substance to decay. As such it is the time taken for the original mass m of a radioactive substance to be change to m/2 .

As such, if a radioactive isotope containing 600,000 radioactive nuclei at 12 noon has a half-life of 2 hours, then At 2pm (after 2 hours),

600,000/2 nuclei would have decayed remaining 600,000/2 nuclei. Both are equivalent to 300, nuclei.

After another 2 hours (at 4pm),

150,000 nuclei would have decayed, remaining 150,000 nuclei.

After another 2 hours (at 6pm), 75,000 nuclei would have decayed thus remaining 75,000 nuclei

Answer 2

Half life of a substance is the time taken for its original mass to decrease by half. In this case, half life is 2 hours
Time taken is 6 hours
Number of half lives will be 3 ( 6/2)
Therefore, New particles = Original particles × (1/2) ∧n
= 600,0000 × (1/2)∧3
= 75, 000 radioactive nuclei
At 6 pm 75, 000 radioactive nuclei will be left