The Periodic Table: Group 7

Group 7: The Halogens

Essentials

The halogens are elements located in Group 7 of the Periodic Table. They include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).
They are called halogens, which means ‘salt-formers’, as they react with metals to form salts.
Halogens are non-metals and have seven electrons in their outermost energy level.

Properties of Halogens

Each halogen atom can gain one electron to achieve a full outer shell of electrons, which leads to the formation of a negative ion (anion).
As you move down Group 7, the halogens become less reactive. This is due to the increased distance of the outer shell from the nucleus, making it harder to attract an electron.
Halogens exhibit different physical properties as you move down the group: fluorine and chlorine are gases, bromine is a liquid, and iodine and astatine are solids at room temperature.
The melting and boiling points of the halogens increase as you go down the group.

Chemical Reactions of Halogens

Halogens react with metals to form ionic salts, in which the halogen atoms become anions.
They can also react with hydrogen to form hydrogen halides, which are acidic gases.
A more reactive halogen can displace a less reactive halogen from a solution of its salt. This series of reactions is known as halogen displacement reactions.

Uses of Halogens

Halogens have diverse applications. For example, chlorine is used in water purification, fluorine is used in toothpaste to prevent tooth decay, and iodine is used as an antiseptic.

Halogens and the Environment

Certain compounds of halogens, such as chlorofluorocarbons (CFCs), can have a detrimental impact on the environment, leading to the depletion of the ozone layer.

Health and Safety Considerations

Halogens can be corrosive and toxic. Proper safety measures should be taken when handling halogens to prevent harm.