Lecture Notes: Hydrogen Emission Spectrum

Introduction to Light and Spectra

• Light and Prisms
  • White light through a prism is refracted, producing a continuous spectrum.
  • The visible spectrum is the part that can be seen with the eyes.
  • A continuous spectrum includes all frequencies of visible light.

Hydrogen Emission Spectrum

• Experiment with Hydrogen Gas Lamp
  • Light from a hydrogen gas lamp, when passed through a prism, shows a line spectrum.
  • Line spectrum: contains only specific frequencies of light.
  • Important terminology: use "frequency" rather than "color" in exams.
  • Hydrogen emission spectrum: line spectrum produced by energized hydrogen gas.

Atomic Structure and Energy Levels

• Hydrogen Atom Model

  • Simple model: nucleus in the center, rings as energy levels.
  • Hydrogen atom has one electron in the ground state (lowest energy level).

• Electron Excitation and Emission

  • Electrons absorb specific frequencies of energy to jump to higher energy levels (excited state).
  • The exact energy difference between levels is required for this transition.
  • Upon returning to a lower energy level, the electron releases the same amount of energy.

Bohr Model and Energy Transitions

• Each frequency/line in the emission spectrum corresponds to an electron's transition between energy levels.

  • Visible spectrum lines result from drops to the second energy level (n=2).

• Specific Transitions in Hydrogen Emission Spectrum

  • Red Line: Transition from 3rd to 2nd energy level.
  • Green Line: Transition from 4th to 2nd energy level.
  • Blue Line: Transition from 5th to 2nd energy level.
  • Violet Line: Transition from 6th to 2nd energy level.

• Energy Level Convergence

  • As energy levels increase, they converge or get closer together.
  • Indicates energy level convergence as they extend outwards in an atom.

Other Spectral Emissions

• UV Spectrum

  • Emissions from drops to the first energy level release much energy, appearing in the UV spectrum.

• Infrared Spectrum

  • Drops to the third energy level release less energy, appearing in the infrared spectrum.

Key Summary Points

1. Emission spectra are produced by electrons releasing energy when dropping to lower energy levels.
2. Hydrogen emission spectrum indicates discrete energy levels that converge at higher energies.
3. Visible spectrum lines result from electron transitions to n=2.
   • Drops to n=1 are in the UV spectrum.
   • Drops to n=3 are in the infrared spectrum.