Unit 11: Nuclear Chemistry
What happens inside an unstable nucleus, the radiation it gives off, and how splitting or fusing nuclei releases energy on a completely different scale.
7 topics · 26 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
11.1 Radioactivity and the Unstable Nucleus
- How it worksHow does an atom's neutron-to-proton ratio determine whether its nucleus stays stable or becomes radioactive?
- How it worksHow does an unstable nucleus release particles or energy to move toward a more stable arrangement?
- Common mistakeWhy doesn't radioactivity mean an atom is somehow contaminated by an outside substance?
- Going furtherWhat happens to an element's identity once its unstable nucleus undergoes radioactive decay?
Your turn1 of 2
Find the neutron-to-proton ratio for a nucleus with 66 protons and 94 neutrons.11.2 Alpha, Beta, and Gamma Decay
- How it worksHow does an alpha particle carry away two protons and two neutrons when a nucleus decays?
- How it worksHow does beta decay convert a neutron into a proton and eject an electron from the nucleus?
- Common mistakeWhy isn't gamma radiation made of particles the way alpha and beta radiation are?
- Going furtherWhat happens to a nucleus's mass and atomic number when it emits a gamma ray instead of an alpha or beta particle?
Your turn1 of 2
A nucleus with atomic number 69 undergoes alpha decay (releasing 2 protons and 2 neutrons). Find the atomic number of the resulting nucleus.11.3 Writing Nuclear Equations
- How it worksHow do you track mass number and atomic number to identify the new element formed by decay?
- How it worksWalk me through using mass and atomic number bookkeeping to find the missing product when uranium-238 undergoes alpha decay.
- Going furtherWhat happens to the mass and atomic numbers in a nuclear equation when a nucleus undergoes beta decay instead of alpha decay?
Your turn1 of 2
A nucleus with mass number 177 undergoes alpha decay, releasing an alpha particle with mass number 4. What is the mass number of the new nucleus formed?11.4 Half-Life
- How it worksHow does each half-life cut the amount of a radioactive substance exactly in half?
- Worked exampleFind how much of a 100 gram radioactive sample remains after three half-lives.
- Worked exampleFind the number of half-lives that pass when a 40 gram radioactive sample decays down to 5 grams.
- Common mistakeWhy doesn't a substance's half-life depend on how much of it you started with?
- Going furtherWhat happens to the fraction of a sample remaining as a fourth and fifth half-life pass?
Your turn1 of 2
Find how much of a 560 gram radioactive sample remains after 6 half-lives.11.5 Nuclear Fission
- How it worksHow does a neutron striking a large nucleus split it apart and release even more neutrons?
- How it worksHow does splitting a large uranium nucleus into two smaller nuclei convert a small amount of mass into a huge amount of energy?
- Going furtherWhat happens to the reaction rate once the neutrons released by one fission event go on to split more nuclei?
Your turn1 of 2
A fission reaction converts 0.224 amu of mass into energy. Find the energy released, in MeV (1 amu = 931.5 MeV).11.6 Nuclear Fusion
- How it worksHow do two light nuclei overcome their repulsion and combine into a heavier nucleus, releasing energy?
- How it worksHow does the sun's own gravity create the pressure and temperature needed to sustain nuclear fusion?
- Common mistakeWhy doesn't nuclear fusion produce the same dangerous long-lived waste that nuclear fission does?
- Going furtherWhat happens to the total mass of the particles involved when hydrogen nuclei fuse into helium?
Your turn1 of 2
Fusing two hydrogen nuclei together requires temperatures far hotter than any furnace or flame found on Earth, conditions that occur naturally only deep inside a star like the sun. Why does it take temperatures hotter than any furnace on Earth to fuse two hydrogen nuclei together?11.7 Uses of Radioactivity
- How it worksHow does carbon-14 dating use a known half-life to estimate the age of once-living material?
- How it worksHow do doctors use a radioactive tracer's decay to image organs or treat cancer without harming the rest of the body?
- Going furtherWhat happens to the accuracy of radiocarbon dating on a sample far older than several half-lives of carbon-14?
Your turn1 of 2
Carbon-14 has a half-life of about 5,730 years. If a sample has gone through 5.72 half-lives of carbon-14 decay since the organism died, approximately how many years old is the sample?