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Glossary Terms
| Term (EN) | Definition | Exam Relevance |
|---|---|---|
| Atomic Number (Z) | Number of protons in nucleus; uniquely identifies element | Atomic structure 2-mark |
| Mass Number (A) | Total protons + neutrons in nucleus | Atomic structure 2-mark |
| Isotopes | Same Z, different A; differ in neutrons | C-14 dating, I-131 therapy |
| Isobars | Same A, different Z | Atomic structure |
| Valency | Number of electrons an atom gains/loses/shares in bonding | Chemical bonding |
| Metalloid | Element with properties between metals and non-metals; e.g., Silicon | Semiconductors |
| Ore | Naturally occurring mineral from which metal can be economically extracted | Metals topic |
| Alloy | Homogeneous mixture of two or more metals (or metal + non-metal) | Alloy composition |
| pH | −log[H⁺]; scale 0–14 measuring acidity/alkalinity | Daily life, body fluids |
| Analgesic | Drug that relieves pain without loss of consciousness; e.g., paracetamol | Drug classification |
| Antibiotic | Chemical that kills or inhibits bacterial growth; e.g., penicillin (1928) | Drug classification |
| Antiseptic | Chemical applied to living tissues to prevent infection; e.g., Dettol | Drug classification |
| DDT | Dichloro-diphenyl-trichloroethane; organochlorine pesticide; banned 1989 (India, agri) | Pesticides, POPs |
| Biomagnification | Increase in concentration of toxins as you move up food chain | DDT in eagles |
| Catenation | Carbon's ability to bond with itself forming long chains | Organic chemistry basis |
| Vulcanisation | Heating rubber with sulphur to form cross-links; Goodyear 1839 | Carbon compounds |
| Calorific Value | Energy released per unit mass of fuel on complete combustion (MJ/kg) | Fuels topic |
| Half-Life (T½) | Time for half the radioactive nuclei to decay | Radioactivity 5-mark |
| Alpha Radiation | ⁴He nucleus; low penetration (stopped by paper); high ionisation | Radiation types |
| Gamma Radiation | High-energy EM waves; highest penetration; stopped by thick lead | Radiation types |
| Nuclear Fission | Heavy nucleus splitting into lighter nuclei + energy (~200 MeV per event) | Nuclear chemistry |
| Nuclear Fusion | Light nuclei combining to form heavier nucleus + energy; powers the Sun | Nuclear chemistry |
| Green Chemistry | Chemical design minimising hazardous substances; 12 principles (1998) | New 2026 syllabus |
| Bleaching Powder | Ca(OCl)Cl; made from Ca(OH)₂ + Cl₂; used for disinfection and whitening | Everyday chemistry |
| Polymer | Large molecule made of repeating monomer units; natural (rubber) or synthetic (nylon) | Carbon compounds |
Sources: NCERT Chemistry (Class 11–12); DST publications; Rajasthan State Mineral Policy; IAEA nuclear data; RPSC Mains PYQ 2013–2024; RPSC 2026 Official Syllabus; Paul Anastas & John Warner, Green Chemistry: Theory and Practice (1998); Stockholm Convention Secretariat.