The half-life of a radioactive substance is the time required for one-half of the atoms of a radioactive isotope to decay into another element, not the time for all of a population to die, half of the lifetime of an unstable nucleus, a constantly changing value, or independent of the decay rate constant.

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A Half-Life Is

Question 37

Multiple Choice

A half-life is

A) the time required for all of a population to die.
B) half of the lifetime of an unstable nucleus.
C) the time required for one-half of a sample of an unstable nuclide to decay.
D) constantly changing.
E) independent of the rate constant for decay.

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