Overview
This lecture explains why fireworks have different colors, explores atomic models, and describes rules and notation for electron configurations.
Fireworks and Atomic Emission
- Firework colors come from metal salts emitting characteristic colors when heated.
- Each color corresponds to a specific wavelength and energy level; red has the longest wavelength (lowest energy), violet the shortest (highest energy).
Atomic Spectra and Bohr Model
- Heated elements emit light of specific colors due to electron energy transitions.
- A spectroscope reveals line spectra, indicating distinct atomic energy levels.
- Niels Bohr's planetary model suggests electrons orbit the nucleus in defined shells (energy levels), each with fixed energy.
- Electrons can jump to higher energy levels (excited state) and release energy as light when returning to lower (ground) state.
- Bohr’s model accurately describes atoms with one electron (e.g., hydrogen).
Quantum Mechanical Model and Orbitals
- Schrödinger, Heisenberg, and de Broglie developed the quantum mechanical model using probability to locate electrons.
- Electrons do not have definite orbits but likely exist in regions called orbitals.
- Each energy level has sub-levels, and sub-levels have a fixed number of orbitals.
- Orbitals: s (spherical, 2 electrons), p (dumbbell-shaped, 6 electrons), d (four lobes, 10 electrons), f (diffuse, 14 electrons).
Electron Configuration and Filling Rules
- Electron configuration shows the arrangement of electrons in their lowest energy state.
- Notation: e.g., 1s²; '1' = energy level, 's' = orbital type, '2' = electrons in orbital.
- Maximum electrons: s (2), p (6), d (10), f (14).
Rules for Electron Configuration
- Aufbau Principle: Fill lower-energy orbitals before higher ones (order: 1s, 2s, 2p, 3s, etc.).
- Pauli Exclusion Principle: Maximum two electrons per orbital, must have opposite spins.
- Hund's Rule: Electrons fill degenerate (equal energy) orbitals singly with same spin before pairing.
Examples
- Lithium (3 electrons): 1s² 2s¹
- Sodium (11 electrons): 1s² 2s² 2p⁶ 3s¹
- Nitrogen (7 electrons): Electrons in p orbitals spread out before pairing.
Key Terms & Definitions
- Metal Salts — Compounds that emit specific colors when heated in fireworks.
- Spectroscope — Device to analyze light and spectra from elements.
- Orbitals — Regions where electrons are likely to be found.
- Electron Configuration — Notation showing the arrangement of electrons by energy levels and orbitals.
Action Items / Next Steps
- Prepare for the next lesson on ionic and covalent bonds.