The flame colours of metal ions are due to

The flame colours of metal ions are due to
  1. Frenkel defect
  2. Schottky defect
  3. metal deficiency defect
  4. metal excess defect.

Solution

This defect arises when a compound has excess metal ion. If a negative ion is absent from its lattice site leaving a hole occupied by electron. The holes occupied by electrons are called F- centres. Greater the number of F-centres greater is the intensity of colour.

Asked in: NEET 2012 (Screening)

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