What is the term for the time required for half of the radioactive atoms in a sample to decay?

What is the term for the time required for half of the radioactive atoms in a sample to decay?

• A. Half-life
• B. Atomic mass
• C. Ionization energy
• D. Electron affinity

Answer: (A)

The time it takes for half of the radioactive atoms in a sample to decay is called the half-life. Because each nucleus has a fixed chance of decaying per unit time, the number of undecayed atoms declines in a predictable, exponential way. The half-life is the specific interval needed for the count to drop from N0 to N0/2, and it is a characteristic property of the isotope, not of the amount you start with. In formulas, N_t = N0 (1/2)^(t / T1/2), where T1/2 is the half-life. Different isotopes have different half-lives, ranging from fractions of a second to billions of years, which is why this concept is so useful in dating and tracing processes. The other terms describe unrelated properties: atomic mass is the mass of the atom, ionization energy is the energy required to remove an electron, and electron affinity is the energy change when adding an electron.

The time it takes for half of the radioactive atoms in a sample to decay is called the half-life. Because each nucleus has a fixed chance of decaying per unit time, the number of undecayed atoms declines in a predictable, exponential way. The half-life is the specific interval needed for the count to drop from N0 to N0/2, and it is a characteristic property of the isotope, not of the amount you start with. In formulas, N_t = N0 (1/2)^(t / T1/2), where T1/2 is the half-life. Different isotopes have different half-lives, ranging from fractions of a second to billions of years, which is why this concept is so useful in dating and tracing processes. The other terms describe unrelated properties: atomic mass is the mass of the atom, ionization energy is the energy required to remove an electron, and electron affinity is the energy change when adding an electron.