Flame tests for metal ions

Identify sodium, potassium, lithium and copper compounds by the colour they give to a flame.

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Objectives

  • Carry out a flame test safely.
  • Match flame colours to metal ions.

Theory

When metal ions are heated strongly, electrons are promoted to higher energy levels. As they fall back they emit light of characteristic wavelengths, giving each metal its own flame colour.

Procedure

  1. Put on your safety goggles and lab coat.
  2. Place a Bunsen burner on the bench and light it.
  3. Put a little sodium chloride in a test tube and carry out a flame test.
  4. Repeat with potassium chloride in a clean tube.
  5. Repeat with lithium chloride.
  6. Repeat with copper(II) chloride.

Precautions

  • Tie back long hair.
  • Clean the wire loop between samples.
Subject
Chemistry
Grade
10–12
Chapter
Qualitative Analysis (Nepal National Curriculum (CDC), grade 11)
Difficulty
Medium
Duration
15 min
Safety level
Medium
Version
1.0

Apparatus

  • Bunsen burner with tripod
  • Test tube

Chemicals

  • Sodium chloride NaCl
  • Potassium chloride KCl
  • Lithium chloride LiCl Harmful
  • Copper(II) chloride CuCl₂ Harmful

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