Chemical bonding

Chemical Bond-

  1. Generally, Chemical bond is said to be formed when minimum energy lowering of 10 kcal/mol is involved when two atoms come closer from infinity.
  2. Except for inert gases, no other element exists as independent atoms under
    ordinary condition.
  3. Hbond possesses a bond energy in the range of 2-10 kcal/mol hence a H-bond is weaker than a chemical bond.
  4. Kossel-Lewis approach (Octet Rule) and its limitations.
  5. C, N, O, F, s-block metals, noble gases (rare gases or zero-valent gases except Xe) obey octet rule in most cases.
  6. The maximum covalency of second-period elements is “four”.
  7. Types of Chemical Bonds-
  8. Ionic Bond – Criterion- Characteristics- Electrovalency- Lattice Energy- Born Haber Cycle- 
  9. Water has maximum dielectric constant (80), (CH3OH- 35), (Acetone- 21), (C2H5OH-27), (Ether-4.1), (Benzene- 2.3) -H2O > CH3OH > CH3CH2OH > CH3COCH3 > CH3OCH3 > C6H6. Ionic compounds are more soluble in the solvents, having high dielectric constant.
  10. H2SO4 and H2O2 have high dielectric constant but these are not a good solvent due to its oxidizing nature.
  11. Covalent Bond- Bond parameters (bond energy, bond length, bond angle)- Lewis dot structures.
  12. If the electronegativities of two bonded atoms differ, then the bond length is smaller than the sum of their covalent radii. dA – B < rA + rB. See here.
  13. Bond length: C-C 154 pm, C=C 134 pm, C#C 120 pm
  14. Bond dissociation energies- factors affecting- examples
  15. Fajan Rule (Covalent character in ionic compounds) – See here -pseudo-noble gas configuration- charge density or ionic potential or polarising power- polarisability- applications Check
  16. Check also
  17. SnO2 is white whereas SnS2 is Yellow.
  18. Diagonal relationship:- Since the value of ionic potential for Be2+ is almost of the same order as that of diagonally situated Al3+. Hence have many similar properties. Similarly, value for Li+ is equal to Mg+2, so have a diagonal relationship.
  19. The high value of ionic potential shows the tendency of forming complex compounds. s-block metals (larger size) doesn’t have the tendency to form complex compounds.
    Exceptions – Li, Be, Mg (small size).
  20. Order of solubility of LiX in water is LiF < LiCl < LiBr < LiI.  In LiI covalent nature is more according to Fajan’s rule but HE > LE, therefore, LiI is more soluble in water.
  21. Order of solubility of MSO4 will be – BeSO4 > MgSO4 > CaSO4 > SrSO4 > BaSO4 (Exception of Fajan’s rule).
  22. Solubility decreases in a period (as ionic nature decreases and covalent nature increases) : NaCl > MgCl2 > AlCl3
  23. For an ionic compound to be soluble in water – Hydration energy > Lattice energy.
  24. Lattice energies calculated for ionic compounds typically fall in the range of 600–4000 kJ/mol (some even higher), covalent bond dissociation energies are typically between 150–400 kJ/mol for single bonds.
  25. H-H bond energy is about 432 kJ/mol and the corresponding bond length is 74 pm (hence covalent radius of a hydrogen atom is 37 pm).
  26. Coordinate bonding (dative bonds) – Complex formation- Lewis acid/ Lewis base interaction –See Here
  27. Check
  28. Variable valency
  29. Hybridization-Check  See Here
  30. Valence bond theory- VSEPR theory
  31. Order of strength of Co – axial overlapping – p – p > s – p > s – s (if n is same)
  32. As the value of n increases, bond strength decreases.- 1s – 2p > 2s – 2p > 3s – 3p
  33. Overlapping of s – s, s – pz, pz – pz (axial) atomic orbitals having unpaired electrons of opposite spin leads to formation of Sigma bond.
  34. Delta bond: It is a special type of lateral overlapping in which all four lobes of d-orbital overlap laterally with another similar d-orbital produce delta bond.
  35. The directional property of different hybrid orbitals will be in following order.
    sp < sp2 < sp3 < sp3d < sp3d2 < sp3d3
  36. sp3d involve dz2.
  37. sp3d2 involve dx2–y2 and dz2.
  38. sp3d3 hybridisation involve dxy, dx2-y2 & dz2 orbitals. See here
  39. Comparison between sp. sp2 and sp3 orbitals-
  40. Bond length decreases in the order sp3 – sp3 > sp2 – sp2 > sp – sp
  41. Bond energy: –C(sp3) – H <  -C(sp2) – H < – C(sp) – H
  42. Formal Charge: See Here
  43. Resonance: See Here
  44. Bond Order: See Here
  45. How can we find the bond order of chlorate ion? See Here
  46. Dipole moment: 1D = 3.336 × 10^(–30) C-m
  47. Order of dipole moment: CH3Cl > CHCl3 > CH2Cl2 > CCl4 = CH4
  48. Between H2O and HF, which has more dipole moments, and why? See Here
  49. How do I compare the dipole moment of R3P=OR3P=O & R3N+−O−R3N+−O− ? See Here
  50. (CO3)2-, and (NO3)- are non-polar.
  51. Molecular orbital theory: See Here
  52. s-p mixing: See here
  53. Back bonding: See here. 
  54. Check
  55. Also this
  56. Further
  57. 3C-4e bond: See Here
  58. Bridge Bond: See here
  59. H-bonding- Viscosity & surface tension of the molecules increases.
  60. Ice is lighter than water because in ice, H2O molecules are extending their H-bonds to full length and six water molecules produce a cage-like structure which is porous in nature leading to smaller mass and larger volume, thus lowering the density.
  61. KHF2 is a red-orange colored solid. KHF2 exists whereas KHCl2, KHBr2, KHI2 do not.See Here
  62. The strength of H-bond :
    F-H ………….. F bond dissociation energy = 41.8 kJ/mol
    O-H ………….. O bond dissociation energy = 29.3 kJ/mol
    N-H ………….. N bond dissociation energy = 12.6 kJ/mol
  63. Which is more water soluble, p hydroxybenzoic acid or o hydroxybenzoic acid? Why? answer
  64. Isomorphism: Different ionic compounds, having same configuration/geometry of ions are isomorphs of each other and phenomenon is known as isomorphism e.g., (a) NaF, MgO (b) ZnSO4 · 7H2O, FeSO4 · 7H2O. (c) All alums M2’SO · M2″(SO4)3 · 24H2O.
  65. d-p “pi” bond: See Here
  66. Isovalent hybridisation: See Here
  67. Why is it that the O-O bond in O2F2 is shorter than that in H2O2? Answer
  68. What is bond order of answer answer 
  69.  Structures: Al2Cl6, 
  70. H3O+
  71. SiO2
  72. Why is Li a very good reducing agent among alkali metals? See Here
  73. The ease of adsoption of the hydrated alkali metal ions on an ion ion exchange resin follow which order a) Li+ b) k+ c) Na+ d) Rb+? See here
  74. How does solubility depend on lattice and hydration energy? See Here
  75. Check
  76. What are three resonance structures of N2O? answer
  77. How can you find the resonance structure for (N3)-? answer
  78. How can I compare stability of :CF2 &:CCl2? See Here
  79. How CAN I COMPARE ACID NATURE of CHCl3 & CHF3? See Here
  80. What is hybridisation of benzene ring having one triple bond and 2 double bond? See here
  81. What are resonance structures of cyanide ion? answer
  82. Why is LiF not soluble in water? answer
  83. What will the hybridisation of NO2? answer
  84. Why is P-O bond stronger than P-Br? See Here
  85. Be(OH)2 is almost insoluble in water while Ba(OH)2 is soluble. Why? answer
  86. With which neutral molecule Clo_ is isoelectronic? answer
  87. What is the most polar bond, CH3Cl, CH3NH2, CH3OH or CH3SH? See Here
  88. Why is the order of the melting point H2O > HF > NH3? answer
  89. What are the various resonating structures of butatriene? answer
  90. See here
  91. Exceptions: Check
  92. BOOKS: See Here

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