Absorption and Emission Spectrum

Historical Context

• Discovery: 1860s discovery that each element emits its own colors of light, known as the emission spectrum.
• Isaac Newton's Contribution: Demonstrated that white light can be separated into a rainbow of colors using a prism.

Emission Spectrum

• Definition: Specific colors emitted by an element when energy is applied.
• Characteristics: Each atom emits a unique series of colors.
• Explanation by Bohr: Electrons transitioning between energy levels emit light.

Absorption Spectrum

• Process: Passing light through a gas results in certain colors being absorbed.
• Energy Levels: Colors closer to purple have higher energy; colors near red have lower energy.
• Absorption and Electron Transition: Light of a specific color and energy can cause an electron to jump to a higher energy level.

Electron Energy Transitions

• Energy Absorption:
  • Electrons absorb specific light colors to move to higher energy levels.
  • Example: Blue light contains energy to move electrons between levels.
  • Absorption spectrum shows missing lines where light is absorbed.
• Energy Emission:
  • Electrons release energy as they fall to lower energy levels.
  • Emission spectrum shows the light emitted, indicating the energy change.
  • Particular light colors indicate the energy difference between levels.

Practical Observations

• Ultraviolet Light: Absorbed and not visible on the absorption spectrum.
• Infrared Light: Absorbed with minimal energy, often not visible in spectrum analysis.
• Emission and Absorption Indicators:
  • Absorption spectrum: Black bars where light is absorbed.
  • Emission spectrum: Colored bars indicating light emitted by atom when electrons descend.

Summary

• Energy Absorption: Electron transitions from lower to higher energy levels absorb light, visible as black bars in an absorption spectrum.
• Energy Emission: Electrons falling from higher to lower energy levels emit light, visible in the emission spectrum.