If there are 400 radioactive atoms in a sample, how many will remain after four half-lives have passed? Enter the exact number as your answer. Do not spell out the number.

25 atoms of the radioactive atoms will remain after 4 half lives.

    Given in the question,

Expression for the amount remaining of a radioactive element after 'n' half lives is given by,

Here, Initial amount

Number of half lives

By substituting the vales of and in the question,

        Therefore, 25 atoms of the radioactive atoms will remain after 4 half lives.

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25 atoms

Explanation:

Given data:

Total number of atoms = 400 atom

Atoms remain after 4 half lives passed = ?

Solution:

At time zero = 400 atom

At first half life = 400 atom/2 = 200 atom

At 2nd half life = 200 atom/2 = 100 atom

At 3rd half life = 100 atom/2 = 50 atom

At 4th half life = 50 atom/2 = 25 atom

Thus, 25 atoms are remained after 4 half lives.

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