The halogens react with metals to produce salts (the word 'halogen' means 'salt former'). For example, chlorine reacts with sodium:
Sodium + chlorine → sodium chloride
2Na(s) + Cl2(g) → 2NaCl(s)
Sodium and chlorine react vigorously when heated, giving an orange flame and clouds of white sodium chloride.
The halogens become less reactive going down group 7. The table describes what is seen when halogens react with iron wool.
|Fluorine||Cold iron wool burns to produce white iron(III) fluoride|
|Chlorine||Hot iron wool burns vigorously to produce orange-brown iron(III) chloride|
|Bromine||Hot iron wool burns quickly to produce red-brown iron(III) bromide|
|Iodine||Hot iron wool reacts slowly in iodine vapour to produce grey iron(II) iodide|
Write a balanced equation for the reaction of iron with chlorine to produce solid iron(III) chloride, FeCl3. Include state symbols.
2Fe(s) + 3Cl2(g) → 2FeCl3(s)
The halogens react with hydrogen to produce compounds called hydrogen halides. For example, chlorine reacts with hydrogen:
Hydrogen + chlorine → hydrogen chloride
H2(g) + Cl2(g) → 2HCl(g)
The table describes what is seen when halogens react with hydrogen.
|Fluorine||Explodes in the cold and dark, forming hydrogen fluoride|
|Chlorine||Explodes with a flame or in sunlight, forming hydrogen chloride|
|Bromine||Vigorous reaction with burning hydrogen, forming hydrogen bromide|
|Iodine||Very slow reaction when heated strongly, forming some hydrogen iodide|
Astatine is placed below iodine in group 7. Use the information to predict the reaction of astatine with hydrogen.
Astatine should react very slowly with hydrogen, even when heated. A little hydrogen astatide should form, which should dissolve in water to form an acidic solution.
Damp litmus paper is bleached white when it is placed in chlorine. If damp blue litmus paper is used, the paper turns red then white.