Quantum Theory and Electron Configurations

Quantum Theory Overview

• Quantum Theory explains behavior at the atomic and subatomic levels.

• Includes concepts like electron configurations and periodicity.

Light and Energy

• Light is a form of energy with oscillating electric and magnetic fields.

• Wavelength ($\lambda$) is the distance between adjacent points (measured in nm).

• Frequency ($
  u$) is the number of wavelengths passing a point per second (Hz).

• Speed of light ($c$) = $3.00 \times 10^8$ m/s.

Wave-Particle Duality

• Light exhibits wave behavior (diffraction, interference) and particle behavior (photoelectric effect).

• Photoelectric Effect: Electrons ejected when light hits metal, with energy dependent on frequency.

Energy Quantization

• Energy (E) of photons is quantized, given by Planck's equation: $E = h
  u$ or $E = \frac{hc}{\lambda}$.

• Planck's constant ($h$) = $6.626 \times 10^{-34}$ J·s.

Bohr Model of Atom

• Electrons occupy specific energy levels; energy levels quantified by $E = -\frac{R_H}{n^2}$.

• Transitions between energy levels result in photon emission/absorption.

Electron Configuration

• Electrons described using quantum numbers: principal ($n$), angular momentum ($l$), magnetic ($ml$), and spin ($ms$).

• Pauli Exclusion Principle: No two electrons can have the same four quantum numbers.

• Aufbau Principle: Electrons occupy the lowest energy orbitals first.

Periodic Properties

• Atomic Radius: Decreases across a period, increases down a group.

• Ionization Energy: Increases across a period, decreases down a group.

• Electron Affinity: Energy change when an electron is added to an atom; trend becomes more negative across periods.

Skills Summary

• Relate wavelength and frequency.

• Calculate photon energy.

• Apply quantum number rules.

• Determine atomic configurations using Aufbau and Hund's rules with periodic trends.