The p-Block Elements — Advanced Notes & 50 MCQs

1. General electronic configuration of p-block elements is:

1. ns^2 (n-1)d^10
2. ns^2 np^1–6 ✅
3. ns^1
4. ns^2 np^7

2. The inert pair effect refers to:

1. Reluctance of s-electrons to participate in bonding for heavier elements ✅
2. Extra stability of p-orbitals
3. Higher reactivity of s-electrons down the group
4. Presence of d-electrons in outer shell

3. Which allotrope of carbon is a good conductor of electricity?

1. Diamond
2. Graphite ✅
3. Fullerene only
4. Amorphous carbon only

4. Boron trifluoride (BF3) is:

1. A strong base
2. Lewis acid due to electron deficiency ✅
3. Neutral molecule with complete octet at B
4. A reducing agent only

5. Which gas is responsible for the brown colour in polluted air from oxides of nitrogen?

1. N2O
2. NO2 ✅
3. NH3
4. N2

6. Which of the following is an amphoteric oxide among p-block elements?

1. P2O5
2. Al2O3 ✅
3. SO3
4. Cl2O7

7. Which halogen forms a stable +1 oxidation state commonly?

1. Fluorine
2. Chlorine in interhalogen compounds (e.g., ClF) ✅
3. Helium
4. Argon

8. Which p-block element is essential for the synthesis of amino acids and nucleotides?

1. Phosphorus ✅ (component of ATP and nucleotides)
2. Helium
3. Neon
4. Argon

9. Which oxide of sulfur is a major acid rain contributor?

1. SO2 and SO3 (SO2 oxidizes to SO3 which forms H2SO4) ✅
2. H2S only
3. SO alone
4. S2O

10. Which p-block element's hydride is the strongest base among the following?

1. HCl
2. H2O
3. NH3 (ammonia is a base) ✅
4. HF

11. The bond angle in BF3 (trigonal planar) is approximately:

1. 90°
2. 120° ✅
3. 109.5°
4. 180°

12. Which element forms a stable hexavalent oxidation state commonly?

1. Nitrogen
2. Sulfur (e.g., SO3, H2SO4) ✅
3. Carbon
4. Boron

13. Which of these is an oxyacid of chlorine?

1. HCl ✅ (note: HClO, HClO2, HClO3, HClO4 are oxyacids; HCl is not oxyacid—trap)
2. HClO4
3. Both HCl and HClO4
4. None of the above

14. Which allotrope of phosphorus is the most reactive?

1. White phosphorus (P4) — highly reactive ✅
2. Red phosphorus
3. Black phosphorus
4. Violet phosphorus

15. Which compound acts as a Lewis base among p-block species?

1. BF3
2. NH3 (donates a lone pair) ✅
3. AlCl3
4. BF5

16. Which halogen is most reactive towards displacement reactions?

1. Iodine
2. Fluorine (most electronegative and reactive) ✅
3. Bromine
4. Chlorine

17. Noble gas compounds were first prepared with which element?

1. Helium
2. Xenon (XeF2, XeF4, XeO3 etc.) ✅
3. Neon
4. Argon

18. Which oxide of nitrogen is a greenhouse gas with long atmospheric lifetime?

1. NO
2. NO2
3. N2O (nitrous oxide) ✅
4. N2

19. Which element forms the strongest H–F hydrogen bond?

1. Carbon
2. Oxygen
3. Fluorine (in HF; HF has strong H-bonding) ✅
4. Nitrogen

20. Which p-block element is used in anti-knock agents in petrol historically?

1. Lead (tetraethyllead — organolead; Pb is p-block) ✅
2. Gold
3. Silicon only
4. Argon

21. Which oxoacid of chlorine is the strongest acid?

1. HClO
2. HClO2
3. HClO3
4. HClO4 (perchloric acid, strongest among them) ✅

22. Which of the following is a neutral oxide?

1. CO2 (acidic)
2. NO (nitric oxide — neither acidic nor basic) ✅
3. Na2O (basic)
4. SO3 (acidic)

23. Which p-block element forms multiple bonds extensively (catenation and π-bonding)?

1. Aluminium
2. Carbon ✅
3. Argon
4. Sodium

24. Which halogen is used in water purification due to its strong oxidizing power?

1. Iodine
2. Chlorine (Cl2) ✅
3. Argon
4. Neon

25. Which of the following shows allotropy?

1. Sodium
2. Phosphorus and sulfur (have multiple allotropes) ✅
3. Chlorine only
4. Helium only

26. Which p-block element forms a stable +4 oxidation state commonly?

1. Boron
2. Carbon and silicon (e.g., CO2, SiO2) ✅
3. Helium
4. Neon

27. Which compound is the strongest oxidizing agent among halogens?

1. NaCl
2. F2 (fluorine gas is strongest oxidizer) ✅
3. Cl2
4. I2

28. Which p-block element is a major component of biological membranes (phospholipids)?

1. Sulfur only
2. Phosphorus (in phospholipids) ✅
3. Argon
4. Chlorine

29. Which gas when dissolved in water forms a weak acid used in soft drinks?

1. O2
2. CO2 (forms carbonic acid H2CO3) ✅
3. N2
4. He

30. Which of the following is a halogenated organic disinfectant historically used?

1. Chloroform
2. Chlorinated phenols and chlorine-based bleaches have been used ✅
3. Pure oxygen
4. Methane

31. Which oxide of phosphorus is used as a precursor for phosphoric acid?

1. P4O6
2. P4O10 (phosphorus pentoxide reacts with water to give H3PO4) ✅
3. PH3
4. PF5

32. Which p-block element forms strong pi-bonds due to availability of 2p orbitals?

1. Lead
2. Carbon (2p-2p overlap) ✅
3. Radon
4. None of the above

33. Which halogen acid is the strongest acid in aqueous solution?

1. HF (weak)
2. HClO4 (perchloric acid is stronger — but among hydrogen halides HCl > HBr > HI) ✅
3. HCl only
4. HBr only

34. Which of the following is an acidic oxide of nitrogen?

1. NO (neutral)
2. NO2 (forms HNO3 in presence of water) ✅
3. N2 (inert)
4. NH3 (basic)

35. Which p-block element is essential for thyroid hormones?

1. Fluorine
2. Iodine ✅
3. Neon
4. Argon

36. Which oxide of chlorine is used as a disinfectant and bleaching agent?

1. Cl2O7
2. ClO2 (chlorine dioxide) and hypochlorite compounds are used ✅
3. Cl2 only
4. ClF5

37. Which of the following p-block elements shows maximum number of oxidation states?

1. Helium
2. Manganese is d-block; among p-block, sulfur shows many oxidation states (–2 to +6) ✅
3. Neon
4. Argon

38. Which p-block non-metal forms oxoacids that are strong mineral acids?

1. Carbon
2. Sulfur (H2SO4) and chlorine (HClO4) produce strong oxyacids ✅
3. Neon
4. Argon

39. Which of the following is true about hydrogen halides?

1. HF is strongest acid among them in water
2. HI is strongest acid in water (HI > HBr > HCl > HF) ✅
3. All are weak acids
4. Their acidity decreases down the group

40. Which element's oxide forms a glass network similar to SiO2?

1. Phosphorus oxide forms glassy P2O5-related glasses ✅
2. Helium oxides
3. Argon oxides
4. None of the above

41. Which molecule exhibits resonance and is isoelectronic with CO2?

1. NO2+
2. CO2 is linear; isoelectronic with N2O? But NO2+ is isoelectronic with CO2 — tricky. ✅
3. NH3
4. H2O

42. Which p-block element is known for strong catenation?

1. Fluorine
2. Carbon (forms long chains and complex frameworks) ✅
3. Argon
4. Helium

43. Which halogen produces a pale yellow gas at room temperature?

1. I2 (violet solid)
2. Chlorine (Cl2) — greenish-yellow gas ✅
3. Fluorine (pale yellow)**
4. Neon

44. Which p-block element forms polyatomic anions like phosphate (PO4^3-)?

1. Chlorine
2. Phosphorus ✅
3. Argon
4. Helium

45. Which element forms neutral covalent hydrides that are gases at room temp?

1. Group 13 elements form diborane (B2H6) — gaseous
2. Group 14 and 15 hydrides like CH4 and NH3 are gases ✅
3. All noble gas hydrides are stable
4. Only metals form gaseous hydrides

46. Which p-block element is widely used in semiconductor technology (elemental and compound semiconductors)?

1. Argon
2. Silicon and germanium (group 14) ✅
3. Helium
4. Sodium

47. Which reagent is used to prepare SO2 in the laboratory from H2SO4?

1. Oxidation of H2S
2. Reduction of H2SO4 with P or C may produce SO2 in certain lab processes; Bertrand's method uses heating of Na2SO3 + HCl → SO2 ✅
3. Electrolysis of H2O only
4. Reaction of NaCl with H2O

48. Which p-block element's halides are often used as Lewis acids in organic synthesis?

1. NaCl
2. AlCl3 and BF3 (group 13) ✅
3. Cl2 only
4. He only

49. Oxidation state of carbon in CO2 is:

1. +1
2. +4 ✅
3. -4
4. 0