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When the alkali metals react with the different halogens (Group 7 of the periodic table), the group of compounds formed are known as the alkali metals halides. Due to the fact that there are a number of different halogens that can react with the alkali metals, you must be prepared to change the halide involved depending on the question being asked.

All alkali metal halides are white solids.

Note that all the halogens are toxic, and so these reactions should be carried out in a fume cupboard.

Lithium

2Li(s) + X₂(g) → 2LiX(s)

Where X is Cl or Br or I

Note that all the reactions of lithium with halogens produce a crimson flame.

Sodium

2Na(s) + X₂(g) → 2NaX(s)

Where X is Cl or Br or I

Note that all the reactions of sodium with halogens produce a yellow flame.

Potassium

2K(s) + X₂(g) → 2KX(s)

Where X is Cl or Br or I

Note that all the reactions of potassium with halogens produce a lilac flame.