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Elements of group 1 give colour in Bunsen Burner due to:
1. Low ionisation potential
2. Low melting point
3. Softness
4. One electron in outermost orbit

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Correct Answer - Option 1 : Low ionisation potential

Concept:

  • Alkali metals lie on the extreme left of the periodic table in Group 1.
  • They have low ionization potential as they have loosely bound electrons.
  • Alkali metals are extremely soft and can be cut with a knife.
  • Alkali metals are highly reactive and some of them react violently in water.
  • Sodium metal is stored in kerosene and potassium and lithium are stored wrapped in Paraffin wax.
  • Most of them are ionic in nature.

Explanation:

  • Flame test:
    • Alkali metals solution when placed in the oxidizing flame of the burner gives a characteristic colored flame.
    • Alkali metals have low ionization enthalpy and the heat supplied provides them with sufficient energy which makes the outermost electron transition to higher energy levels.
    • As higher energy levels are not stable, the electron in excited states falls back to ground levels, which emits radiation of characteristic color.
    • Thus each ion gives a unique color.
    • Li gives a Magenta color flameNa gives a golden-yellow flame, Potassium gives a lilac flame and Cesium gives purple flame.
    • The flames are used to detect the presence of Metals in a salt sample.
    • Metals with high ionization potential do not respond to this test.

Hence, the color given by alkali metals in Bunsen Burner is due to their Low Ionisation potential.

  • Other metals that give these tests are Calcium, Barium, Strontium, etc.
  • Each flame has a unique color and is used to identify the presence of the metals.

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