Group 7 - chemical properties
atomThe smallest part of an element that can exist. of group 7The vertical column of non-metal elements next to group 0 in the periodic table, also called the halogens. elementA substance made of one type of atom only. all have seven electronSubatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. in their outer shell. This means that the halogenAn element placed in group 7 of the periodic table, which starts with fluorine and ends with astatine. The name 'halogen' means 'salt-producing' because halogens produce a range of salts when they react with metals. all have similar chemical reactionA change in which atoms are rearranged and joined together differently to form new substances. They often involve energy changes..
When a group 7 element takes part in a reaction, its atoms each gain one electron. These atoms form negatively charged ionElectrically charged particle, formed when an atom or molecule gains or loses electrons.. The ions have a stable arrangement of electrons, with a complete outer shell.
Reactions with metals
The halogens react with metals to produce saltThe substance formed when the hydrogen ion in an acid is replaced by a metal ion.. The salts are made up of ions, which are held together by ionic bondingIonic bonding forms between two atoms when an electron is transferred from one atom to the other, forming a positive-negative ion pair.. For example, chlorine reacts with sodium:
sodium + chlorine 鈫 sodium chloride
2Na(s) + Cl2(g) 鈫 2NaCl(s)
Sodium and chlorine react vigorously when heated, giving an orange flame and clouds of white sodium chloride.
In group 7, the reactivityA measure of how vigorously a substance will react. The more reactive it is, the greater its reactivity and the more vigorous its reactions will be. of the elements decreases down the group. The table describes what happens when halogens react with iron wool.
| Halogen | Reaction |
| 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 |
| Halogen | Fluorine |
|---|---|
| Reaction | Cold iron wool burns to produce white iron(III) fluoride |
| Halogen | Chlorine |
|---|---|
| Reaction | Hot iron wool burns vigorously to produce orange-brown iron(III) chloride |
| Halogen | Bromine |
|---|---|
| Reaction | Hot iron wool burns quickly to produce red-brown iron(III) bromide |
| Halogen | Iodine |
|---|---|
| Reaction | Hot iron wool reacts slowly in iodine vapour to produce grey iron(II) iodide |
Question
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) 鈫 2FeCl3(s)
Reactions with non-metals
The halogens react with non-metals such as hydrogen. When a halogen reacts with hydrogen, the product is a compoundA substance formed by the chemical union of two or more elements. called a hydrogen halide. For example, chlorine reacts with hydrogen:
hydrogen + chlorine 鈫 hydrogen chloride
H2(g) + Cl2(g) 鈫 2HCl(g)
The hydrogen halides are gases at room temperature. They dissolveWhen a substance breaks up and mixes completely with a solvent to produce a solution. in water to produce acidicHaving a pH lower than 7. solutionMixture formed by a solute and a solvent.. Hydrogen chloride dissolves in water to produce hydrochloric acid, HCl(aq).
The table describes what happens when halogens react with hydrogen. It shows that the reactivity of the elements decreases down the group.
| Halogen | Reaction |
| 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 |
| Halogen | Fluorine |
|---|---|
| Reaction | Explodes at room temperature and in the dark, forming hydrogen fluoride |
| Halogen | Chlorine |
|---|---|
| Reaction | Explodes with a flame or in sunlight, forming hydrogen chloride |
| Halogen | Bromine |
|---|---|
| Reaction | Vigorous reaction when warmed with hydrogen, forming hydrogen bromide |
| Halogen | Iodine |
|---|---|
| Reaction | Very slow reaction when heated strongly, forming some hydrogen iodide |
Question
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.