13 - Electronic structure of Atoms

Electronic Structure of Atoms

Wave Properties of Light

  • Light behaves like a wave, similar to ripples in water.

  • Wavelength (λ): The length of a wave, measured in meters.

  • Frequency (f): Number of cycles per second, measured in Hertz (Hz).

    • 1 Hz = 1 cycle/second

  • Relationship: As wavelength increases, frequency decreases, and vice versa.

Speed of Light

  • Speed of Light: Approximately 3.0 x 10^8 meters/second.

  • Relationship: Wavelength (λ) x Frequency (f) = Speed of Light (c).

    • If one variable increases, the other decreases to maintain the constant speed of light.

Electromagnetic Radiation

  • Electromagnetic radiation describes light as a wave.

  • Higher frequency radiation (e.g., x-rays and gamma rays) has higher energy and can be harmful.

  • Lower frequency radiation (e.g., radio waves) has lower energy.

Black Body Experiment

  • Conducted by Max Planck, demonstrating quantized energy levels.

  • More frequency was expected to mean more intensity, leading to a continuous increase in energy, but it instead peaked and dropped off.

  • Energy levels are quantized—no transitions exist between levels.

Photoelectric Effect

  • Light can behave as both a wave and a particle (photons).

  • Experiment showed that increasing light frequency, not intensity, releases electrons with constant kinetic energy.

  • Relevant Formula: E = h*f, where E is energy, h is Planck's constant, and f is frequency.

  • Indicates that light travels in discrete packets of energy (photons).

Atomic Spectrum

  • Different elements emit light at certain frequencies, not continuously.

  • Bohr's Model: Electrons in atoms exist in quantized energy levels and can only jump between these levels (emission and absorption).

Key Relationships

  • As wavelength increases, frequency decreases.

  • As frequency increases, energy increases.

  • Electrons move between quantized energy levels by absorbing or emitting energy:

    • Emission: Electron drops to a lower energy level, emitting energy.

    • Absorption: Electron gains energy and jumps to a higher level.