Chemical Bonding & Stoichiometry Cheat Sheet

Key Definitions

• Chemical Bonding: Attraction between atoms to form molecules.

• Molecular Geometry: 3D arrangement of atoms in a molecule.

• Polarity: Distribution of electrical charge over atoms in a molecule.

• Intermolecular Forces: Forces between molecules (e.g., hydrogen bonding).

• Acids and Bases:

• Acid: Proton donor (H⁺).

• Base: Proton acceptor.

• Stoichiometry: Relationship between quantities of reactants and products.

Important Concepts

Chemical Bonding

• Ionic Bonds: Transfer of electrons between metals & nonmetals.

• Covalent Bonds: Sharing of electrons between nonmetals.

Molecular Geometry

• VSEPR Theory: Shapes determined by electron pair repulsion.

• Common Shapes: Linear, trigonal planar, tetrahedral.

Polarity

• Polar Molecules: Unequal sharing of electrons (e.g., H₂O).

• Nonpolar Molecules: Equal sharing of electrons (e.g., O₂).

Intermolecular Forces

• Types:

• London Dispersion

• Dipole-Dipole

• Hydrogen Bonding

Stoichiometry Laws

• Lavoisier: Mass is conserved in chemical reactions. ✅

• Proust: Compounds have fixed proportions by mass. ✅

Key Formulas

• Moles: Amount of substance (6.022 x 10²³ particles).

• Mass %: (mass of solute / total mass) x 100 ✅

Common Mistakes to Avoid

Common Mistake: Confusing empirical and molecular formulas; empirical is the simplest ratio, while molecular reflects actual numbers of atoms.

Memory Tricks

Tip: "VSEPR" — Valence Shell Electron Pair Repulsion for predicting molecular shapes.

Key Diagrams

Molecular Shapes:
      H
      |
  H - C - H
      |
      H
Linear: A-B-C
Trigonal Planar: A
                / \
               B   C
Tetrahedral:    A
              / | \
             B  C  D

Stoichiometric Calculations

• Balancing Equations: Ensure mass conservation.

• Excess Reactant: Reactant that remains after the reaction. ⚠️

• Purity: (actual yield / theoretical yield) x 100 ✅

• Yield: Measure of efficiency of a reaction.

Tip: Always check units in stoichiometric calculations to ensure consistency.