This tutorial visualizes key ideas in chemical bonding: how electron domains determine molecular geometry (VSEPR), how atomic orbitals combine into hybrid orbitals, and how ionic vs covalent bonding differ.

Module 1: VSEPR Theory & Molecular Geometry

VSEPR (Valence Shell Electron Pair Repulsion) states that electron domains — bonding pairs (atoms) and lone pairs — repel each other and arrange to minimize repulsion, giving predictable geometry. Notation AX_nE_m: A = central atom, X = bonding pairs, E = lone pairs.

Module 2 (Hybridization): Carbon can be sp³ (tetrahedral, e.g. methane), sp² (trigonal, e.g. ethene with a π bond), or sp (linear, e.g. ethyne with two π bonds). Overlap of hybrid orbitals gives σ bonds; unhybridized p orbitals overlap laterally to form π bonds.

Module 3 (Ionic vs Covalent): In covalent bonding, electrons are shared (e.g. a figure-eight molecular orbital). In ionic bonding, electrons transfer from one atom to another; the resulting ions form a lattice. Lattice energy U (Coulomb’s law) measures the strength of that ionic structure:

Simulation

The interactive simulator is below. Use the controls to explore the concepts described above.

Usage

Module 1 – VSEPR Sandbox: Use Bonding pairs (+/−) and Lone pairs (+/−) to set the number of electron domains (total 2–6). Choose a Preset (e.g. CH₄, H₂O, CO₂) or build custom geometry. The 3D molecule updates immediately: central atom (silver), bonding partners (light blue), bonds (white cylinders; double/triple shown), lone pairs (translucent green lobes). The panel shows AXE notation, geometry name, and ideal bond angles. Toggle Show bond angles and Show polarity vector (red arrow = net dipole direction for asymmetric molecules).

Module 2 – Hybridization & Orbital Overlap: Select Hybridization (sp³, sp², or sp) and an example molecule. The 3D view shows hybrid lobes (yellow) and unhybridized p orbitals (red/blue phases). Use the Orbital opacity slider to adjust transparency. Click Form Bond to show the σ bond (yellow pill between atoms) and π bonds (purple) for sp²/sp. The detail panel explains the hybridization type.

Module 3 – Ionic vs Covalent & Lattice Energy: Choose a Preset (H₂, HCl, NaCl, NaF, MgO) or use Custom. Electronegativity diff and Internuclear distance sliders control the two-atom view: atom sizes reflect the preset (e.g. H smaller than Cl); the bond is a capsule of shared electron density (yellow → red-orange as polarity increases). When EN diff ≥ 1.7 the bond is ionic: cloud hides, cation (silver) shrinks, anion (green) grows. Bond type and Lattice energy U (k|q₁q₂|/r) are shown. For ionic presets, Generate Crystal Lattice toggles a 4×4×4 rock-salt lattice; changing the sliders updates the lattice in real time (spacing from internuclear distance).

3D view (all modules): Drag to rotate, scroll to zoom. Iso, Front, Top, Side set camera views; Z+ / Z− zoom; arrow buttons pan.

Polarity vector (Module 1)

The polarity vector (red arrow) is the vector sum of bond directions from the central atom. Symmetric geometries (CO₂, CH₄, SF₆) cancel to zero; bent (H₂O) or pyramidal (NH₃) show a net direction. This is a geometry-only model (no electronegativity).

VSEPR examples (Module 1)

Limitations

• VSEPR is qualitative: it predicts idealized shapes and approximate angles but not exact bond angles, which depend on electronegativity, atom size, and multiple-bond effects.
• Geometry-only polarity: the polarity vector sums bond directions, not real dipole moments — it ignores electronegativity differences and lone-pair contributions.
• Simplified lattice energy: U ≈ k|q1q2|/r is a single ion-pair Coulomb estimate; real lattice energy uses the full Madelung sum and Born repulsion (Born–Landé equation).
• Localized-bond picture: hybridization and σ/π bonds are a teaching model; it does not compute true molecular orbitals, resonance, or delocalization.