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UPPCS Chemistry Gap Sheet: Atoms and Nuclear Chemistry.
UPPCS has asked 20 of these. 2 have not been asked yet. Lock the first list, then read the second: it holds what UPPCS has not used yet.
First, the concept
An element is identified by its proton count. Changing neutrons makes an isotope; changing electrons makes an ion. The nucleus carries almost all the mass of an atom.
Radioactivity changes an unstable nucleus. Fission splits a heavy nucleus, while fusion joins light nuclei. A moderator slows neutrons; it is not the nuclear fuel.
✅ Already asked (20)
Particles and identity
- Atomic number · Number of protons in the nucleus.
- Electron · Negatively charged particle outside the nucleus.
- Proton · Positively charged nuclear particle.
- Neutron · Uncharged nuclear particle; discovered by James Chadwick.
- Electron–positron pair · Particle and antiparticle with equal mass and opposite charge.
- Quarks · Protons and neutrons contain quarks; quarks are elementary particles.
- Nuclear size · Typical nuclear dimensions are of order 10⁻¹⁵ m.
Related atoms
- Isotopes · Same proton count, different neutron counts.
- Isobars · Different elements with the same mass number.
- Isotones · Different elements with the same neutron count.
- Deuterium · Hydrogen isotope with one proton and one neutron.
- Heavy water · D₂O; nominal molecular mass 20 u; used as a moderator in some reactors.
Nuclear processes
- Radioactivity · Spontaneous decay of unstable nuclei; a nuclear property.
- Alpha radiation · Helium nuclei; low penetration but strong ionising power.
- Gamma radiation · High-energy electromagnetic radiation; no charge or rest mass.
- Nuclear fission · Splitting a heavy nucleus; used in conventional nuclear reactors.
- Nuclear fusion · Joining light nuclei; powers the Sun and hydrogen bombs.
- Carbon-14 dating · Dates once-living material; half-life about 5,730 years.
- Uranium–lead dating · Used for very old rocks, unlike carbon dating.
- Half-life · Time for half the radioactive nuclei in a sample to decay.
❌ Not asked yet (2)
Items marked 'asked in other exams' have come in UPSC or other state exams, not yet in UPPCS.
🔒 2 items not asked yet
Particles and identity: 1 · Nuclear processes: 1
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⚠️ Isotopes share atomic number, not mass number; a hydrogen bomb uses fusion.
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