Group 7 (Halogens)

Halogens are found in Group 7 of the periodic table.
This group includes fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).
They exist as diatomic molecules, meaning they’re made up of two atoms.
Halogens are non-metals with coloured vapours.
Their reactivity decreases as you move down the group.
The various halogens have distinct physical states at room temperature, with fluorine and chlorine as gases, bromine as a liquid and iodine and astatine as solids.

Halogens decrease in reactivity down the group.
They have increasing melting and boiling points moving down the group.
The various states (gas, liquid, solid) of halogens at room temperature offers a direct reflection of these increasing boiling points.
Halogens generally have a high electron affinity or a strong attraction to electrons.

Halogens have seven electrons in their outer shell, hence their name which means “salt-forming”.
They are extremely reactive, particularly with alkali metals and hydrogen.
In reactions, halogens gain an electron to achieve a stable electron configuration.
These reactions usually lead to the formation of salts.

Halogens are toxic and can be hazardous to health; for precaution, many are stored in sealed containers.
Bromine is especially dangerous; it’s a corrosive, toxic liquid which gives off poisonous fumes.
Iodine is less dangerous, but it sublimates to produce a purple vapour which is harmful in large quantities.
Always ensure good ventilation when working with halogens, and try to avoid inhalation or skin contact.