p-Block Elements (Class XII Chemistry)

Inert pair effect: Inertness of s subshell electrons (i.e. ns2) towards bond formation. As we move down the group, the lower oxidation state gets stabilised.

Q. Which of the two is more stable? SbCl₅ or SbCl₃

Q. Why is Bi (V) a stronger oxidant than Sb (V)?     (2009 set 1)

Q. The stability of + 5 oxidation state decreases down the group in group 15 of the periodic table. (2010 Set 3)

Q. Tendency to form pentahalides decreases down the group in  group 15 of the periodic table (2010 Set 3)

Disproportionation: Element in a particular oxidation state undergoes self-oxidation and self-reduction.

Q. Can HNO₃ and H₃PO₄ undergo disproportionation reaction?

Q. Does hydrolysis of XeF₆ lead to disproportionation reaction?

Non-metallic hydrides-Bond dissociation enthalpy and basicity of hydrides decreases down the group, Reducing character of hydrides increases down the group, Smaller size and inavailability of d-orbitals affect basic strength

Q. Ammonia is a stronger base than phosphine. (2008 Set 1)

Q. The acidic strength decreases in the order HCl > H₂S > PH₃ (2010 Set 3)

Q. Which is the stronger acid in aqueous solution? HF or HCl

Q. Ammonia has higher boiling point than phosphine. Explain

Q. Bond angle in phosphine is lesser than ammonia. Explain

Q. H₂O is liquid but H₂S is gas. Explain

Q. Oxygen is a gas but sulphur is a solid? ( 2012 Set 3)

Q. All the bonds in SF₄ are not equivivalent. (2012 Set 3)

Colour of halogen compounds-Halogen absorbs radiations in visible region which excites electrons to higher energy region, so the amount of energy required for excitation is different for each halogen.

Q. The halogens are coloured, why? (2012 Set 3)

Non-metallic halides-Hexa halides of elements are stable owing to sterically protected six halide atoms, Covalent character-Polarising power: Charge/ radius ionic character is opposite of covalent character

Q. NF3 is an exothermic compound but NCl3 is endothermic compound. (2012 Set 3)

Q. Why are pentahalides more covalent than trihalides?

Q. SF₆ is kinetically an inert substance. (2011 Set 1)

Q. Solid phosphorus pentachloride behaves as an ionic compound. (2010 Set 3)

Q. SF4 is easily hydrolysed whereas SF6 is not easily hydrolysed. (2009 Set 1)

Catenation: This self-linking property is due to higher bond strength

Q. Sulphur has greater tendency for catenation than oxygen. (2011 Set 3, 2012 Set 3)

Q. Catenation tendency is weaker in nitrogen than phosphorus. Explain (2012 Set 3)

Q. The tendency of catenation decreases down the group. Explain

Interhalogen compounds: Two or more different halogen atoms reacting with each other to form compounds.

Q. Interhalogen compounds are strong oxidising agents. (2007, Set 1)

Q. In general interhalogen compounds are more recative than halogens. Why?

Q. Why ICl is more reactive than I₂? (NCERT, Intext 7.31, 2012 Set 3)

Q. ClF3 molecule has a T-shaped structure and not a trigonal planar one. (2010, Set 3)

Structures of Oxoacids: phosphorus (2007), sulphur (2007),

Structures of Fluoride: sulphur (2008), xenon (2008, 2009), bromine (2009)

Interhalogen compounds (2007)

Basicity of group 15 elements (2008, 2009)

1. Structures of PCl₅, H2SO₃, H₂SO₄, H₂S₂O₈, H₂S₂O₇, HOCl, HClO₂, HClO₃, HClO_4, N₂O_5, XeOF4
2. Complete the following reaction:
   • P₄ + NaOH + H₂O →
   • P₄ + SO₂Cl₂ →
   • POCl₃ + H2O→
   • KMnO₄ + HCl →
   • NaOH + Cl₂ →
   • Cu + HNO₃ (dil) →
   • XeF₄ + O₂F₂ →
3. Conceptual questions:

• NF₃ is an exothermic compound whereas NCl₃ is not.
• NH₃ is a stronger base than PH₃. Why?
• Arrange the following in order of the indicated property:
  • F₂, Cl₂, Br₂, I₂ in increasing order of bond dissociation enthalpy
  • HF, HCl, HBr, HI in increasing order of acidic strength
  • NH₃, PH₃, AsH₃, SbH₃, BiH₃ in increasing order of basic strength
• What are interhalogen compounds?

Wishing you all the very best for exams.

Team MeritNation