67. Chemistry: Atomic Structure, Metals & Non-Metals, Ores & Alloys, Acids/Bases/pH, Drugs, Pesticides, Carbon Compounds, Fuels, Radioactivity, Green Chemistry

CORE Key Points at a Glance

1. 1

   Atomic Structure

   • Atom has a nucleus (protons + neutrons) surrounded by electrons in energy shells
   • Atomic number (Z) = number of protons; uniquely identifies each element
   • Mass number (A) = protons + neutrons
2. 2

   Isotopes

   • Atoms of the same element with same Z but different A
   • Example: Carbon-12 and Carbon-14
   • Carbon-14 used in radiocarbon dating; half-life = 5,730 years
3. 3

   Metals vs Non-Metals

   • Metals: electropositive, malleable, ductile, good conductors
   • Non-metals: electronegative, brittle, poor conductors
   • Exception: graphite (non-metal, conducts electricity)
   • Exception: mercury (metal, liquid at room temperature)
4. 4

   Key Ores

   • Bauxite — primary ore of aluminium
   • Haematite (Fe₂O₃) — iron ore
   • Galena (PbS) — lead ore
   • Chalcopyrite (CuFeS₂) — copper ore
   • India's bauxite reserves (~3 billion tonnes) are the 5th largest globally
5. 5

   Alloys

   • Alloys are homogeneous mixtures of metals
   • Stainless steel: Fe + Cr (10–11%) + Ni — corrosion-resistant
   • Brass: Cu + Zn; Bronze: Cu + Sn
   • Duralumin: Al + Cu + Mn + Mg — used in aircraft
   • Solder: Pb + Sn — used for electrical joints
6. 6

   pH Scale

   • pH scale ranges 0–14: pH < 7 = acidic; pH = 7 = neutral; pH > 7 = basic/alkaline
   • Human blood pH = 7.35–7.45
   • Stomach acid (HCl) pH ≈ 1.5–2
   • Seawater pH ≈ 8.1
7. 7

   Drug Categories

   • Analgesics relieve pain: aspirin, paracetamol
   • Antibiotics kill/inhibit bacteria: penicillin (Alexander Fleming, 1928)
   • Antipyretics reduce fever
   • Antiseptics prevent infection on living tissue
   • Disinfectants kill microbes on non-living surfaces
8. 8

   Pesticides

   • Organochlorine pesticides (DDT, BHC/lindane) — highly persistent, bioaccumulate in food chains
   • Most banned under the Stockholm Convention (2004)
   • Safer alternatives: neonicotinoids, pyrethroids, integrated pest management (IPM)
9. 9

   Carbon Compounds

   • Carbon forms millions of compounds due to catenation (self-linking) and tetravalency (4 bonds)
   • Alkanes: CₙH₂ₙ₊₂ — saturated hydrocarbons
   • Alkenes: CₙH₂ₙ — one double bond
   • Alkynes: CₙH₂ₙ₋₂ — triple bond
10. 10

    Petroleum and Fuels

    • Petroleum (crude oil) is a mixture of hydrocarbons, refined by fractional distillation
    • Fractions: LPG (below 30°C), petrol (30–70°C), kerosene (150–270°C), diesel (250–350°C)
    • Calorific values: hydrogen (142 MJ/kg) > LPG (~50) > petrol (~47) > coal (~30 MJ/kg)
11. 11

    Radioactivity

    • Spontaneous emission of radiation from unstable nuclei
    • Alpha (α): helium nuclei (2p+2n); low penetration, stopped by paper
    • Beta (β): electrons or positrons; moderate penetration
    • Gamma (γ): high-energy EM radiation; highest penetration, stopped only by thick lead/concrete
12. 12

    Green Chemistry

    • 12 Principles formulated by Paul Anastas & John Warner, 1998
    • Aims to reduce or eliminate hazardous substances in chemical design, synthesis, and use
    • Key principles: atom economy, renewable feedstocks, avoiding auxiliary solvents
    • Also: energy efficiency, catalytic reagents over stoichiometric
13. 13

    Nuclear Fission vs Fusion

    • Nuclear fission: U-235 or Pu-239 splits; releases ~200 MeV per fission; powers reactors
    • Nuclear fusion: hydrogen isotopes form helium; releases ~17.6 MeV per D-T reaction
    • Fusion requires temperatures of ~100 million °C
    • Fusion is the energy source of the Sun
14. 14

    Polymer Chemistry

    • Natural polymers: rubber (polyisoprene), cellulose, starch, proteins
    • Synthetic polymers: nylon (polyamide, 1935), PVC (polyvinyl chloride), Teflon (PTFE), Bakelite (first synthetic plastic, 1907)
    • Rubber vulcanisation: heating with sulphur (Charles Goodyear 1839) improves elasticity and durability