Question

Which statements best describe half-lives of radioactive isotopes? Check all that apply.

The half-life varies depending on the isotope.
The half-life is the same for every isotope.
Half-lives are always only minutes long.
Half-lives range from fractions of a second to billions of years.
The half-life of a particular isotope is constant.
The half-life of a particular isotope changes constantly.

Answer 1

Correct statements:
- The half-life varies depending on the isotope. — True. Different isotopes have different decay probabilities and thus different half-lives.
- Half-lives range from fractions of a second to billions of years. — True. Observed half-lives span many orders of magnitude.
- The half-life of a particular isotope is constant. — True (under normal conditions). The decay constant for a given nuclide is fixed, so its half-life is a characteristic property. (Minor exceptions exist under extreme conditions for certain decay modes, e.g., electron-capture rates can change if the atom is fully ionized.)

Incorrect statements:
- The half-life is the same for every isotope. — False.
- Half-lives are always only minutes long. — False.
- The half-life of a particular isotope changes constantly. — False.