How much of the sample will remain after a half-life?

The correct answer is 2) 60 grams.

Thallium-208 has a half-life, which means that after one half-life, half of the original sample will remain. Since you start with a 120 gram sample, after one half-life, you will have:

[ text{Remaining sample} = frac{120 text{ grams}}{2} = 60 text{ grams}. ]

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The correct answer is 2) 60 grams.

Explanation: The half-life of a radioactive substance is the time it takes for half of the material to decay. Since you start with a 120 gram sample of Thallium-208, after one half-life, half of that amount will remain. Therefore, after one half-life, you would have:

120 grams ÷ 2 = 60 grams remaining.

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