Study Notes on Atomic Structure and Bonding
Atomic Structure Fundamentals
- Atom is comprised of electrons, protons, and neutrons.
- Atomic number (Z): number of protons = number of electrons in neutral atom.
- Atomic mass (A): mass of protons + mass of neutrons.
- Isotopes: same element with different atomic masses.
- Atomic weight: weighted average of atomic masses of isotopes.
Key Concepts in Atomic Structure
- Bohr Model: Electrons occupy discrete orbitals with quantized energy levels.
- Quantum Numbers: Define electron states based on energy levels and orbital types.
Electron Configurations
- Electrons occupy lowest available energy states (Valence electrons are key for bonding).
- Stable configurations have filled s and p subshells (e.g., Noble gases).
- Chemical properties driven by valence electron configurations.
Bonding Forces
- Attractive and repulsive forces govern atomic interactions.
- At equilibrium, attractive and repulsive forces balance.
- Bonding energy and thermal properties (Tm, E) depend on bond type.
Types of Bonding
Ionic Bonding
- Occurs between cations (+) and anions (−) through electron transfer.
- Non-directional and high bonding energy.
- Example: NaCl (sodium chloride).
Covalent Bonding
- Electrons shared between atoms of similar electronegativity.
- Directional bonds affecting molecular properties.
- Example: CH₄ (methane).
- Delocalized electron clouds shield positive ion cores; non-directional.
- Common in metals and alloys.
Secondary Bonding (Van Der Waals)
- Interaction between dipoles (permanent and induced).
- Weaker than primary bonds, but important in molecular compounds (e.g., hydrogen bonding).