Question

Which statements describe half-life? Check all that apply.

Each isotope has a half-life that is different from the half-life of other isotopes.
All isotopes have the same half-life.
The half-life of an isotope is always the same.
The half-life of an isotope changes constantly.
An isotope’s half-life is affected by temperature, pressure, density, and concentration.
An isotope’s half-life is not affected by temperature, pressure, density, or concentration.

Answer 1

Which apply (true) and which do not (false):

- Each isotope has a half-life that is different from the half-life of other isotopes. — True. Every radioactive nuclide has its own characteristic decay constant/half‑life (different nuclides usually have different half‑lives).

- All isotopes have the same half-life. — False.

- The half-life of an isotope is always the same. — True, in the normal sense: the half‑life is an intrinsic property and does not change under ordinary physical or chemical conditions. (Caveat: there are rare, small exceptions under special conditions — see below.)

- The half-life of an isotope changes constantly. — False.

- An isotope’s half-life is affected by temperature, pressure, density, and concentration. — Generally false. Under ordinary laboratory and earth conditions these factors do not change nuclear decay rates. (Caveat: some decay modes—notably electron capture or processes sensitive to the atom’s electron configuration—can be slightly altered by chemical environment or extreme ionization/stellar conditions.)

- An isotope’s half-life is not affected by temperature, pressure, density, or concentration. — True in the usual practical sense, with the exceptions noted above.

Short summary: Half‑life is an intrinsic, usually constant property that differs between nuclides. Very small changes can occur in special cases (e.g., electron‑capture isotopes, fully ionized atoms in stars), but for most purposes half‑lives are unaffected by temperature, pressure, concentration, etc.