Nuclear Chemistry Questions and Answers

Answer: C

¹⁴C decays by β decay and ¹⁴O by positron emission.

¹⁴C has 6 protons and 8 neutrons, more neutrons than the stable ¹²C. A neutron-rich nucleus moves towards stability by turning a neutron into a proton and emitting an electron (β⁻), giving ¹⁴N.

¹⁴O has 8 protons and only 6 neutrons, so it is proton-rich. It turns a proton into a neutron and emits a positron (β⁺), also giving ¹⁴N.

The options naming a single mode for both nuclei ignore that they lie on opposite sides of the band of stability, and option D reverses them.

Answer: D

The radioactive isotope of hydrogen is tritium.

Hydrogen has three natural isotopes: protium (one proton, no neutron), deuterium (one proton and one neutron) and tritium (one proton and two neutrons). Protium and deuterium are stable, but tritium is radioactive: it decays by beta emission to helium-3 with a half-life of about 12.3 years.

Helium is a different element, not an isotope of hydrogen, and it is also the product of tritium's decay. Protium and deuterium are hydrogen isotopes, but stable ones.