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Pro 🔒~15 min

Molecular Structure & Chemical Bonding

VSEPR theory and molecular geometry in 3D

How it works

Chemical bonding determines molecular geometry, polarity, and reactivity. Covalent bonds form when atoms share electrons; the electronegativity difference determines polarity (nonpolar < 0.5, polar 0.5-1.7, ionic > 1.7). VSEPR theory predicts 3D geometry: electron pairs (bonding + lone) arrange to minimize repulsion. Lone pairs repel more strongly than bonding pairs, compressing bond angles. Linear (180°): CO₂, BeCl₂. Trigonal planar (120°): BF₃. Tetrahedral (109.5°): CH₄. Bent (104.5°): H₂O (2 lone pairs). Trigonal pyramidal (107°): NH₃ (1 lone pair). Octahedral (90°): SF₆. Net molecular dipole moment = vector sum of all bond dipoles.

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Step-by-step

  1. Select a molecule from the dropdown.
  2. The 3D model builds automatically showing atoms, bonds, and lone pairs.
  3. Rotate with mouse to inspect all angles.
  4. Toggle dipole arrows to see individual bond dipoles and the net molecular dipole.
  5. Switch to spacefill mode to see van der Waals radii.

Key formulas

  • VSEPR: electron pairs repel→geometry minimizes repulsion\text{VSEPR: electron pairs repel} \to \text{geometry minimizes repulsion}Valence Shell Electron Pair Repulsion theory
  • H2O: bent (104.5°), NH3: trigonal pyramidal (107°)\text{H}_2\text{O: bent (104.5°), NH}_3\text{: trigonal pyramidal (107°)}Lone pairs compress bond angles below ideal
  • μ⃗=q⋅d(dipole moment: charge×distance)\vec{\mu} = q \cdot d \quad (\text{dipole moment: charge} \times \text{distance})Dipole moment — measure of bond polarity

Frequently asked questions

Water has 2 bonding pairs and 2 lone pairs. What geometry does VSEPR predict, and what is the bond angle?
4 electron pairs → tetrahedral electron geometry. But 2 lone pairs → bent molecular geometry. Bond angle ≈ 104.5° (less than 109.5° due to lone pair compression).
Why is CO₂ nonpolar even though C=O bonds are polar?
CO₂ is linear (180°). The two C=O bond dipoles point in exactly opposite directions → they cancel → net dipole = 0.
What is the electron geometry and molecular geometry of NH₃?
N has 3 bonding pairs + 1 lone pair = 4 electron pairs → tetrahedral electron geometry. Molecular geometry = trigonal pyramidal (ignore lone pair).
SF₆ has 6 bonding pairs around S. What geometry does it adopt and what are the bond angles?
6 electron pairs → octahedral geometry, all bond angles 90°. No lone pairs, so molecular geometry = octahedral.