By going through these Maharashtra State Board 12th Science Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 students can recall all the concepts quickly.

Maharashtra State Board 12th Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18

Atomic, physical and chemical properties of group 16,17 and 18 elements-

Group 16 elements-

O to Po:

  • Atomic size, M.P., B.P., Density increase
  • Ionisation enthalpy, electronegativity decrease
  • Hydrides (H2X) : Bond angle, bond energy decrease Reducing power increases
  • Oxides (EO2, EO3) (E = S, Se, Te, Po)
  • Halides (EX6, EX4, EX2) (E = S, Se, Te)
  • Reacts with metals to form compounds

Allotropes :

  • O : O2, O3 (Ozone)
  • S : Rhombic, monoclinic, cyclo-S6
  • Se : red, grey
  • Te : Crystalline, amorphous
  • Po : α, β

Group 17 elements-

F to I (At):

  • Atomic size, Density increase
  • Ionisation enthalpy, electronegativity decrease
  • (Haloacids, HX) : Acidity, reducing character increase Stability decrease
  • Oxides of halogens (Most of them are unstable)
  • Interhalogen compounds
  • Metal halides

Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18

Group 18 elements-

He to Xe (Rn):

  • Atomic size, density, M.P., B.P., increase
  • Ionisation enthalpy, decreases
  • Chemically inert towards hydrogen, oxygen
  • krypton and Xenon form fluorides

Oxoacids of sulphur-
Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 1

Oxoacids of halogens-
Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 2
Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 3

O2 – Preparation –
Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 4

O2 –
2Ca + O2 → 2CaO
C + O2 → CO2
Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 5

Simple oxides-

Acidic (CO2, SO2, etc.)
Basic (CaO, BaO, etc.)
Amphoteric (Al2O3, Zno, etc.)

Ozone –

Oxidising property: (i) PbS(S) + 4O3(g) → PbSO4 + 4O2(g)
(ii) 2KI + H2O +O3 →2KOH + I2 + O2
(iii) NO(g) + O3(g) → NO2(g) + O2(g)
Bleaching property O3 → O + O2
Reducing property : BaO2 + O3 → BaO + 2O2
H2O2 + O3 → H2O + 2O2

Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18

SO2 – preparation

S(S) + O2(g) → SO2(g)
Na2SO3 + H2SO4(aq) → Na2SO4 + H2O(I) + SO2(g)
Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 6

SO2 –

Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 7
2NaoH + SO2 → Na2SO3 + H2O
Na2SO3 + H2O + SO2 → 2NaSO3
2Fe3+ + SO2 + 2H2O → 2Fe2+ + SO4 2- + 4H+

H2SO4 (Manufacture)—Contact process—(Catalyst V2O5)

H2SO4 – 

C + 2H2SO4 → CO2 + 2H2O + 2SO2
S + 2H2SO4 → 3SO2 + 2H2O
Cu + 2H2SO4 → CuSO4 + SO2 + 2H2O
Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 8
NaCl + H2SO4 → NaHSO4 + HCl
KNO3 + H2SO4 → KHSO4 + HNO3
CaF2 + H2SO4 → CaSO4 + 2HF

Chlorine Preparation –

MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O
4NaCl + MnO2 + 4H2SO4 → 4NaHSO4 + MnCl2 + 2H2O + Cl2
Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 9
NaCl ⇌ Na+ + Cl–

Cl2 –

2Al + 3Cl2 → 2AlCl3
P4 + 6Cl2 → 4PCl3
H2 + Cl2 → 2HCl
8NH3 (Excess) + 3Cl2 → 6NH4Cl + N2
2Ca(OH)2 + 2Cl2 → Ca(OCl)2 + CaCl2 + 2H2O
Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 10
2FeSO4 + H2SO4 + Cl2 → Fe2(SO4)3 + 2HCl
Cl2 + H2O → HCl + HOCl

HCl : Preparation –

Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 11

HCl –

HCl(g) + H2O(l) → H3O+ + Cl–(aq)
NH3 + HCl → NH4Cl
Au + 4H+ + NO–3 + 4Cl– → AuCl–4 + NO + 2H2O

Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18

Interhalogen Compounds-

Maharashtra Board Class 12 Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 12

Compounds of Xenon-

Compound Hybridisation Structure
(i) XeF2 sp3d linear
(ii) XeF4 sp3d2 square planar
(iii) XeF6 sp3d3 distorted octahedral
(iv) Xe03 sp3 pyramidal