Chemistry of Representative Elements Class 12 One-Liners & MCQs

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Chapter 1

  1. The Periodic Table is a systematic arrangement of elements based on atomic numbers, electronic configuration, and properties.
  2. The long form of the Periodic Table consists of 7 horizontal rows (periods) and 18 vertical columns (groups).
  3. Elements are divided into s-block, p-block, d-block, and f-block based on orbital filling.
  4. s-block elements (Groups IA & IIA) have valence configurations ns¹ (alkali metals) and ns² (alkaline earth metals).
  5. p-block elements (Groups IIIA to VIIIA) have valence configurations ns² np¹ to ns² np⁶.
  6. Atomic radius increases down a group due to increasing energy levels.
  7. Ionization energy decreases down a group as outermost electrons are farther from the nucleus.
  8. Electronegativity decreases down a group due to increasing atomic radii.
  9. Group IA (alkali metals) have the largest atomic radii in their periods.
  10. Group IIA (alkaline earth metals) show increasing atomic radii from Be to Ra.
  11. Halogens (F, Cl, Br, I, At) reactivity is determined by bond enthalpies and redox reactions.
  12. Bond enthalpies of halogens decrease from Cl to I due to increasing bond length; F is an exception.
  13. Acidity of hydrogen halides: HF < HCl < HBr < HI.
  14. Oxidizing strength of halogens: F₂ > Cl₂ > Br₂ > I₂.
  15. Reducing strength of halide ions: I⁻ > Br⁻ > Cl⁻ > F⁻.
  16. Chlorine can displace Br and I from salts: 2NaBr + Cl₂ → 2NaCl + Br₂.
  17. Sulphuric acid (H₂SO₄) is produced via the Contact Process.
  18. Contact Process steps: S → SO₂ → SO₃ → H₂S₂O₇ → H₂SO₄.
  19. H₂SO₄ is a strong oxidizing agent, dehydrating agent, sulphonating agent, and dibasic acid.
  20. Uses of H₂SO₄: fertilizer production, petroleum refining, and metal processing.
  21. Diagonal relationships: Li–Mg, Be–Al, B–Si.
  22. Li & Mg have similar atomic radii and electronegativities.
  23. Be & Al have the same electronegativity (1.5) and show passivity with concentrated HNO₃.
  24. B & Si are metalloids with close electronegativity and similar density.
  25. Aluminum is used in coins, alloys, and utensils.
  26. Sulphur is used in the production of H₂SO₄, H₂S, and pesticides.
  27. Chlorine is used in plastics, bleaching powder, and water purification.
  28. Borax is used in cleaning, laundry, and cosmetics.
  29. Alum is used in water purification and leather tanning.
  30. Ammonia is used in fertilizers, nitric acid, and refrigeration.
  31. Alkali metals (Group IA) have low ionization energy and high reactivity.
  32. Alkaline earth metals (Group IIA) have higher ionization energy than alkali metals.
  33. p-block elements show variable oxidation states.
  34. Halogens are strong oxidizing agents due to their high electronegativity.
  35. Fluorine is the strongest oxidizing agent among the halogens.
  36. Iodide ion (I⁻) is the strongest reducing agent among the halide ions.
  37. Sulphuric acid (H₂SO₄) is highly soluble in water and corrosive.
  38. H₂SO₄ is used in battery manufacture and cleaning.
  39. The diagonal relationship leads to similarities in the properties of diagonally placed elements.
  40. s-block elements (alkali and alkaline earth metals) are highly reactive metals.