Chemistry · Inorganic Chemistry

Chemical Bonding and Molecular Structure formulas for JEE

Every Chemical Bonding and Molecular Structure formula you need for JEE, grouped by concept.

FormulasRevision notes
19 formulas5 concepts
01Covalent Bonding and Lewis Structures02Ionic Bonding03Bond Parameters and Polarity04Valence Bond Theory and Hybridization05Molecular Orbital Theory
01

Covalent Bonding and Lewis Structures

1 formula

Formal Charge

F.C.=V−L−12SF.C. = V - L - \frac{1}{2}S

Formal charge on an atom in a Lewis structure. V = Valence electrons, L = Lone pair (non-bonding) electrons, S = Shared (bonding) electrons.

applies whenApplicable for assigning charges in Lewis structures to find the most stable resonance form.
formal chargelewis structureoctet rule
02

Ionic Bonding

2 formulas

Born-Landé Equation

U=−NAMz+z−e24πϵ0r0(1−1n)U = -\frac{N_A M z^+ z^- e^2}{4\pi\epsilon_0 r_0} \left(1 - \frac{1}{n}\right)

Calculates the theoretical lattice energy of an ionic crystal considering electrostatic attractions and Born repulsions.

applies whenStandard ionic crystals.
lattice energyionic crystaljee-advanced

Lattice Formation Equation

M+(g)+X−(g)→MX(s)M^+(g) + X^-(g) \rightarrow MX(s)

Equation representing the release of lattice enthalpy during the formation of an ionic solid from its gaseous constituent ions.

lattice enthalpyionic bond
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03

Bond Parameters and Polarity

8 formulas

Average Bond Enthalpy

Average Bond Enthalpy=∑ΔaHNumber of bonds broken\text{Average Bond Enthalpy} = \frac{\sum \Delta_a H}{\text{Number of bonds broken}}

Calculated for polyatomic molecules where identical bonds have different dissociation enthalpies due to changing chemical environments.

applies whenPolyatomic molecules like H2O, CH4.
bond enthalpypolyatomic

Bond Length (Covalent Radii)

R=rA+rBR = r_A + r_B

The equilibrium internuclear distance R between two bonded atoms, approximately the sum of their covalent radii.

applies whenSingle covalent bond between atoms A and B.
bond lengthcovalent radius

Debye Conversion Factor

1 D=3.33564×10−30 C m1 \text{ D} = 3.33564 \times 10^{-30} \text{ C m}

Conversion factor connecting Debye units to the SI unit of Coulomb-meters.

dipole momentunits

Dipole Moment (Scalar)

μ=Q×r\mu = Q \times r

The product of the magnitude of separated charge Q and the distance r between the centers of positive and negative charges.

applies whenPolar covalent molecules.
dipole momentpolarityscalar

Dipole Moment (Vector)

μ⃗=q×r⃗\vec{\mu} = q \times \vec{r}

Vector representation of the dipole moment.

applies whenPolar covalent molecules.
dipole momentpolarityvector

Hannay-Smith Equation

% Ionic Character=16∣χA−χB∣+3.5(χA−χB)2\% \text{ Ionic Character} = 16|\chi_A - \chi_B| + 3.5(\chi_A - \chi_B)^2

Estimates the percentage of ionic character in a bond based on the electronegativity difference of the two atoms.

applies whenEstimations using Pauling electronegativities.
ionic characterelectronegativityjee-advanced

Percentage Ionic Character (Dipole)

% Ionic Character=(μobsμcal)×100\% \text{ Ionic Character} = \left(\frac{\mu_{obs}}{\mu_{cal}}\right) \times 100

Calculates the ionic character of a polar covalent bond by comparing the observed dipole moment to the theoretical moment of a 100% ionic bond.

ionic characterdipolejee-advanced

Resultant Dipole Moment

μnet=μ12+μ22+2μ1μ2cos⁡θ\mu_{net} = \sqrt{\mu_1^2 + \mu_2^2 + 2\mu_1\mu_2\cos\theta}

Vector sum of two bond dipoles oriented at an angle theta to each other.

applies whenPolyatomic molecules.
dipole momentvectorjee-advanced
04

Valence Bond Theory and Hybridization

2 formulas

Bond Angle in sp^n Hybridization

cos⁡θ=−1n\cos\theta = -\frac{1}{n}

Relates the bond angle theta between equivalent hybrid orbitals to the hybridization index n.

applies whenEquivalent sp^n hybrid orbitals (no lone pair distortions).
hybridizationbond anglejee-advanced

Steric Number for Hybridization

H=12(V+M−C+A)H = \frac{1}{2}(V + M - C + A)

Determines the number of hybrid orbitals. V=Valence e-, M=Monovalent atoms, C=Cationic charge, A=Anionic charge.

applies whenCentral atom bonding.
hybridizationvseprjee-advanced
05

Molecular Orbital Theory

6 formulas

Antibonding Molecular Orbital

σ∗=ψA−ψB\sigma^* = \psi_A - \psi_B

Wave function of an antibonding MO formed by destructive interference, resulting in a nodal plane between nuclei.

motantibonding orbital

Bonding Molecular Orbital

σ=ψA+ψB\sigma = \psi_A + \psi_B

Wave function of a bonding MO formed by constructive interference, resulting in higher electron density between nuclei.

motbonding orbital

Bond Order

B.O.=12(Nb−Na)\text{B.O.} = \frac{1}{2}(N_b - N_a)

Calculates the number of covalent bonds. Nb is the number of bonding electrons, Na is the number of antibonding electrons.

applies whenMolecular Orbital Theory.
motbond order

LCAO Wave Function

ψMO=ψA±ψB\psi_{MO} = \psi_A \pm \psi_B

Linear combination of atomic orbitals describing the overall molecular orbital wave function.

applies whenAtomic orbitals must have comparable energies and proper symmetry.
motwave functionlcao

MO Energy Sequence (B2, C2, N2)

σ1s<σ∗1s<σ2s<σ∗2s<(π2px=π2py)<σ2pz<(π∗2px=π∗2py)<σ∗2pz\sigma 1s < \sigma^* 1s < \sigma 2s < \sigma^* 2s < (\pi 2p_x = \pi 2p_y) < \sigma 2p_z < (\pi^* 2p_x = \pi^* 2p_y) < \sigma^* 2p_z

Energy filling order for B2, C2, and N2 where sp mixing pushes the sigma 2pz orbital higher in energy than the pi 2px/2py orbitals.

applies whenMolecules exhibiting significant 2s-2p orbital mixing.
motenergy levelssp mixing

MO Energy Sequence (O2, F2)

σ1s<σ∗1s<σ2s<σ∗2s<σ2pz<(π2px=π2py)<(π∗2px=π∗2py)<σ∗2pz\sigma 1s < \sigma^* 1s < \sigma 2s < \sigma^* 2s < \sigma 2p_z < (\pi 2p_x = \pi 2p_y) < (\pi^* 2p_x = \pi^* 2p_y) < \sigma^* 2p_z

Standard energy filling order for molecular orbitals in homonuclear diatomic molecules O2 and F2.

applies whenMolecules without significant 2s-2p mixing.
motenergy levelsaufbau
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