Chemical Bonding and Molecular Structure: One-Page Formula Sheet

Chemical Bonding and Molecular Structure — formula sheet

Formulas

• Steric number = σ bonds + lone pairs on central atom
• Bond order = (N_b − N_a)/2
• Dipole moment μ = q × d
• % ionic character ≈ μ_observed / μ_ionic × 100

Key ideas

• Hybridisation from steric number: 2 sp, 3 sp², 4 sp³, 5 sp³d, 6 sp³d²
• Lone pairs distort ideal bond angles
• MOT bond order = (bonding − antibonding)/2
• O₂ is paramagnetic (two unpaired electrons)

Traps to avoid

• Confusing shape with geometry when lone pairs exist
• Wrong MOT order for B₂, C₂, N₂ vs O₂, F₂
• Ignoring resonance when comparing bond lengths

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