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Chemistry
Nuclear Chemistry
Nuclear Chemistry
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Nuclear chemistry studies changes that occur in atomic nuclei rather than in electron arrangements. It explains radioactivity, nuclear decay, transmutation, fission, fusion, and the energy released from the nucleus. This field matters in medicine, power generation, archaeology, space science, and radiation safety. Unlike ordinary chemical reactions, nuclear reactions can change one element into another.
Key Facts
- Mass number: A = protons + neutrons
- Atomic number: Z = number of protons
- Alpha decay: A decreases by 4 and Z decreases by 2
- Beta minus decay: neutron becomes proton, so Z increases by 1
- Half-life formula: N = N0(1/2)^(t/T)
- Nuclear energy comes from mass change: E = mc^2
Vocabulary
- Radioactivity
- Radioactivity is the spontaneous emission of particles or energy from an unstable atomic nucleus.
- Isotope
- An isotope is an atom of the same element with the same number of protons but a different number of neutrons.
- Half-life
- Half-life is the time required for half of a radioactive sample to decay.
- Alpha particle
- An alpha particle is a helium nucleus made of 2 protons and 2 neutrons emitted during alpha decay.
- Nuclear fission
- Nuclear fission is the splitting of a heavy nucleus into smaller nuclei, releasing energy and often neutrons.
Common Mistakes to Avoid
- Confusing chemical reactions with nuclear reactions is wrong because chemical reactions rearrange electrons, while nuclear reactions change the nucleus itself.
- Forgetting to conserve mass number and atomic number in nuclear equations is wrong because both totals must balance across the reaction.
- Thinking half-life means the entire sample disappears after one half-life is wrong because only half of the radioactive nuclei decay in each half-life period.
- Treating alpha, beta, and gamma radiation as equally penetrating is wrong because alpha particles are least penetrating, beta particles are moderately penetrating, and gamma rays are highly penetrating.
Practice Questions
- 1 A sample of iodine-131 has a half-life of 8 days. If the original sample is 80 g, how much remains after 24 days?
- 2 Uranium-238 undergoes alpha decay. Write the balanced nuclear equation and identify the daughter nucleus.
- 3 Explain why gamma emission changes the energy of a nucleus but does not change the element or mass number.