Halogens
Chemistry: AQA GCSE Higher, topic 1.1.23
Halogens (Group 7) - Properties
Elements in group 7 in the periodic table are called halogens. Halogens have 7 electrons in their outer shell. They are very reactive because they easily accept an electron into this outer shell. They have similar properties and react in similar ways.
7 outer electrons
- Halogens are in group 7 and so have 7 electrons in their outer shell.
- When they react, they gain 1 electron to get a full outer shell.
- By gaining 1 electron, they form a negative ion.
Diatomic molecules
- In their elemental form, halogens share electrons to make diatomic molecules (molecules made of pairs of atoms).
Salts
- When a metal atom transfers its outer electron to a non-metal atom (like a group 7 atom), salts are formed.
- The result is a compound where all the ions have a full outer shell.
Reactivity
- As you move down the group, the halogens decrease in reactivity. This is because:
- The atoms gain more electron shells.
- So, the distance between the outer electron shell and the nucleus increases.
- So, the attraction between the nucleus and the electron (to be gained from another element) decreases.
- So, the distance between the outer electron shell and the nucleus increases.
Test yourself on Halogens
How are halogens structured in their elemental form?
Why do halogens become less reactive as you go down the group?
Why do all halogens have similar chemical properties?
What happens when a metal atom reacts with a halogen atom to form a salt?
Why does a halogen ion have an overall negative charge?