Of the two isotopes of iodine, 196Pb and 206Pb, one is nonra-dioactive and one decays by positron emission. Which does which? Explain.

Verified step by step guidance

1. Step 1: First, let's clarify what isotopes are. Isotopes are atoms of the same element that have different numbers of neutrons, and therefore different mass numbers. The isotopes in question are both of lead (Pb), not iodine, and have mass numbers of 196 and 206.
2. Step 2: Positron emission is a type of radioactive decay. In this process, a proton in the nucleus of an atom is converted into a neutron, and a positron (a particle with the same mass as an electron but with a positive charge) is emitted.
3. Step 3: The stability of an isotope is determined by the ratio of neutrons to protons in its nucleus. If the ratio is too high or too low, the isotope is likely to be radioactive. For lead, the most stable isotopes have around 125 neutrons.
4. Step 4: The isotope 206Pb has 82 protons and 124 neutrons (206 - 82 = 124), which is close to the ideal ratio for stability. Therefore, it is likely to be the nonradioactive isotope.
5. Step 5: On the other hand, the isotope 196Pb has 82 protons and 114 neutrons (196 - 82 = 114), which is further from the ideal ratio. Therefore, it is likely to be the isotope that decays by positron emission.

Key Concepts

Isotopes

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This results in different atomic masses for the isotopes. For iodine, the isotopes mentioned (196Pb and 206Pb) differ in their neutron count, which affects their stability and radioactive properties.

Radioactivity and Decay Modes

Radioactivity is the process by which unstable atomic nuclei lose energy by emitting radiation. There are several decay modes, including alpha decay, beta decay, and positron emission. Positron emission occurs when a proton in the nucleus is converted into a neutron, releasing a positron and a neutrino, which is a key feature of certain radioactive isotopes.

Stability of Nuclei

The stability of a nucleus is determined by the ratio of protons to neutrons and the overall binding energy. Isotopes with a balanced ratio tend to be stable, while those with too many or too few neutrons compared to protons are often radioactive. In the case of iodine isotopes, one may be stable (non-radioactive) while the other undergoes positron emission due to instability.