Atomic emission spectra

1. Definition and Key Concepts

• Atomic emission spectra are produced when a gas is heated or an electric current is passed through it.
• Electrons in atoms absorb energy and move to a higher energy level (excited state), which is unstable.
• When electrons return to their ground state, they emit energy in the form of light (photons).

2. Characteristics of Atomic Emission Spectra

• The wavelength (colour) of emitted light depends on the energy difference between the excited and ground states.
• Only certain frequencies of light are emitted, producing a line spectrum unique to each element.
• Colours outside the visible range, such as ultraviolet and infrared, are not visible.

3. Applications of Atomic Emission Spectra

• Element Identification: Each element has a unique emission spectrum, allowing scientists to identify substances.
  • Sodium $(Na)$ → Yellow light.
  • Barium $(Ba)$ → Green light.
  • Strontium $(Sr)$ → Red light.
• Fireworks: Colours are produced by different metallic salts.
• Astronomy: Scientists use emission spectra to analyse distant stars and planets.

4. Key Takeaways

• Emission spectra are unique "fingerprints" for elements.
• Excited electrons release photons when returning to lower energy levels.
• Used in chemical analysis, fireworks, and astronomy.