Fundamentals of Atomic and Molecular Chemistry

Mar 1, 2025

Lecture Notes on Atomic and Molecular Chemistry

Atomic Structure

  • Atoms: Basic building units of matter.
    • Consist of a core (protons + neutrons) and electrons.
    • Different elements determined by the number of protons.
  • Electron Shells: Electrons exist in shells; valence electrons are in the outermost shell.
  • Periodic Table: Groups and periods reflect the structure of atoms.

Periodic Table:

  • Groups: Columns with same number of valence electrons.
  • Periods: Rows with same number of electron shells.
  • Atomic Properties:
    • Mass increases left to right.
    • Isotopes: Variants with different neutron numbers.

Chemical Bonds

  • Ions: Charged atoms, cations (positive) and anions (negative).
  • Types of Bonds
    • Covalent Bonds: Sharing of electrons between atoms.
    • Ionic Bonds: Transfer of electrons between atoms resulting in oppositely charged ions.
    • Metallic Bonds: Electrons shared across a lattice of metal atoms.
  • Bond Strength: Ranked from Ionic > Covalent > Metallic > Hydrogen > Van der Waals.

Molecular Composition

  • Molecules and Compounds:
    • Molecule: Two or more bonded atoms.
    • Compound: Molecule with at least two different elements.
  • Isomers: Same molecular formula, different structures.

Quantum Mechanics and Electrons

  • Quantum Numbers: Define electron properties and positions (n, l, ml, ms).
  • Subshells and Orbitals: Spatial regions for electron probabilities (s, p, d, f).
  • Aufbau Principle: Order of filling electron shells.

Chemical Reactions

  • Types: Synthesis, decomposition, single replacement, double replacement.
  • Stoichiometry: Ratios of reactants/products based on conservation of mass.
  • Activation Energy: Energy required to initiate reaction, affected by catalysts.

Energy in Reactions

  • Enthalpy: Heat content of a system.
    • Exothermic: Releases heat.
    • Endothermic: Absorbs heat.
  • Gibbs Free Energy: Determines reaction spontaneity.

States of Matter

  • Solids: Fixed structure, particles only vibrate.
  • Liquids: Free-moving particles with fixed volume.
  • Gases: Free-moving particles filling available space.
  • Plasma: Ionized gas at high energy states.

Mixtures

  • Homogeneous Mixtures: Uniform composition, e.g., solutions.
  • Heterogeneous Mixtures: Non-uniform, e.g., suspensions and colloids.

Acids, Bases, and pH

  • Brondsted-Lowry Theory: Acids donate protons, bases accept them.
  • pH Scale: Measures acidity based on hydronium ion concentration.

Redox Reactions

  • Oxidation and Reduction: Transfer of electrons between substances.
  • Oxidation Numbers: Imaginary charges to track electron flow.

Intermolecular Forces

  • Dipoles and Hydrogen Bonds: Affect molecule interactions and states.
  • Van der Waals Forces: Weak, temporary dipoles.

Properties of Water

  • Polarity: Makes water a versatile solvent.
  • Hydrogen Bonds: Contribute to water’s properties.

These notes cover fundamental concepts of atomic structure, chemical reactions, bonds, quantum mechanics, and states of matter which are essential for understanding chemistry.