Lesson 5: Chemical Bonding & Molecular Geometry
Atoms bond together to form compounds. The type of bond depends on whether electrons are transferred (ionic) or shared (covalent). The arrangement of those bonds determines the shape of the molecule — and shape determines nearly everything about how a molecule behaves.
Key Concepts
Ionic Bonds
Form between a metal and a nonmetal. The metal loses electrons (becomes a cation, +) and the nonmetal gains them (becomes an anion, −). Electrostatic attraction holds them together. Example: NaCl (table salt).
Covalent Bonds
Form between two nonmetals. Electrons are shared between atoms. Single bond = 1 shared pair. Double bond = 2 shared pairs. Triple bond = 3 shared pairs. Example: H₂O, CO₂, N₂.
Electronegativity
The tendency of an atom to pull electrons toward itself. If two atoms have very different electronegativities → ionic bond. Similar electronegativities → covalent bond. Slightly different → polar covalent (unequal sharing).
Lewis Dot Structures
Show valence electrons as dots around an element symbol. Each atom tries to achieve a full outer shell (8 electrons = octet rule). Shared pairs become bonds; unshared pairs are lone pairs.
VSEPR & Molecular Shape
Electron pairs repel each other and spread out as far as possible. This gives molecules their 3-D shapes: linear (CO₂), bent (H₂O), tetrahedral (CH₄), trigonal planar (BF₃).
🔬 Virtual Lab: Bond Type Identifier
Drag the electronegativity slider for each atom. The bond type updates in real time based on the electronegativity difference.
✅ Check Your Understanding
1. What type of bond forms between sodium (EN=0.9) and chlorine (EN=3.2)?
2. In a polar covalent bond, electrons are:
3. Water (H₂O) has a bent shape because of: