When a group 7 element takes part in a reaction, its atoms each gain one electron. These atoms form negatively charged ions. The ions have a stable arrangement of electrons, with a complete outer shell.
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.
In group 7, the reactivity of the elements decreases down the group. The table describes what happens 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 non-metals such as hydrogen. When a halogen reacts with hydrogen, the product is a compound called a hydrogen halide. For example, chlorine reacts with hydrogen:
hydrogen + chlorine → hydrogen chloride
H2(g) + Cl2(g) → 2HCl(g)
The table describes what happens when halogens react with hydrogen. It shows that the reactivity of the elements decreases down the group.
|Fluorine||Explodes at room temperature and in the dark, forming hydrogen fluoride|
|Chlorine||Explodes with a flame or in sunlight, forming hydrogen chloride|
|Bromine||Vigorous reaction when warmed with hydrogen, forming hydrogen bromide|
|Iodine||Very slow reaction when heated strongly, forming some hydrogen iodide|
Astatine is 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 small amount of hydrogen astatide should form, which dissolves in water to form an acidic solution.