Chemistry Formulas for Chemical Bonding
1. Necessary condition for an ionic solid to be dissolved in water
Hydration Energy > Lattice Energy
2. Order of melting and boiling points of certain compounds
NaF > NaCl > NaBr > NaI; MgO > CaO > BaO
3. No Bond is 100% Ionic
4. Force of attraction between two oppositely charged ions in vacuum (air) as per Coulombs Law
F = q1q2/r2
5. Order of the Lattice Energy of some compounds
· LiX > NaX > KX > RbX > CsX (where X = F, Cl, Br, I)
· MgO > CaO > SrO > BaO
· MgCO3 > CaCO3 > SrCO3> BaCO3
· BaSO4 > SrSO4 > CaSO4> MgSO4
· Mg(OH)2 > Ca(OH)2 > Sr(OH)2 > Ba(OH)2
· Bivalent Ions-Bivalent Ions > Univalent Ions-Bivalent Ions or Bivalent Ions-Univalent Ions > Univalent Ions- Univalent Ions
6. Example of some compounds which contains more than one type of bond
· NaOH, KOH, Na2CO3 (Ionic Bond, Covalent Bond)
· CO, NH3.BF3, [Co(NH3)3Cl3] (Dative Bond, Covalent Bond)
· NH4Cl, CuSO4, K4[Fe(CN)6], [Cu(NH3)4]SO4 (Dative Bond, Ionic Bond, Covalent Bond)
· CuSO4.5H2O (Hydrogen Bond, Dative Bond, Ionic Bond, Covalent Bond)
7. Double bond or triple bond is always shorter than corresponding single bond
8. As S-Orbital is smaller than P-Orbital so bond length decrease with increase in S-character
SP3 C-H = 1.093 Å (as in Alkanes)
SP2 C-H = 1.087 Å (as in Alkenes)
SP C-H = 1.057 Å (as in Alkynes)
9. Bond length increases if size of bonded atom is increases with given atom
HI > HBr > HCl > HF
10. Bond distance is directly proportional to Atomic size
11. Order of bond strength (or bond energy) of different hydrogen halides
H-F > H-Cl > H-Br > H-I
12. Bond energy is directly proportional to bond order
Triple Bond > Double Bond > Single Bond
13. Formula of Dipole Moment
Dipole moment (µ) = Electronic Charge (e) x Distance (d)
14. Unit of Dipole Moment
Debye (D)
1D = 1 x 10-18e.s.u. cm
SI unit of Dipole Moment is = Coulomb-Meter (C-m)
1D = 3.336 x 10-30 C-m
15. Dipole Moment of some substances
Substance with Formula | Dipole Moment (D) |
HF | 1.91 |
H2O | 1.84 |
SO2 | 1.60 |
NH3 | 1.46 |
NF3 | 0.24 |
CH3Cl | 1.86 |
HCl | 1.03 |
H2S | 1.10 |
HBr | 0.78 |
HI | 0.38 |
16. Formula to calculate percentage ionic character of covalent bond
% Ionic Character = (Observed dipole moment x 100)/Dipole moment for 100% ionic bond
17. Order of polarizing power of cations
Li+ > Na+ > K+ > Rb+> Cs+
Be2+ > Mg2+ > Ca2+ > Sr2+> Ba2+
Al3+ > Mg2+ > Na+
18. Order of polarizing power of anions
N3- > O2- > F-
P3- > S2- > Cl-
19. Chemistry Formula of Bond Order
Bond Order = [Nb-Na]/2
Where,
Na = Number of electrons in antibonding molecular orbitals
Nb = Number of electrons in bonding molecular orbitals
20. Some molecules with their bond order, bond length and bond dissociation energy
Molecule | Bond Order | Bond Length (pm) | Bond Dissociation Energy (kJ/mol) |
F2 | 1 | 142 | 158 |
O2 | 2 | 121 | 498 |
N2 | 3 | 110 | 945 |
21. Bond Order in compounds which exhibits Resonance
Bond Order = (Total No. of bonds between two atoms)/(Total No. of resonating structures)