Halogens - Properties
Chemistry: Edexcel IGCSE, topic 8.1.5
Halogens (Group 7) - Properties
Elements in group 7 in the periodic table are called halogens. They 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 go down the group, the halogens become less reactive. This is because:
- The atoms gain more electron shells.
- The outer electron shell is further from the nucleus.
- The attraction between the nucleus and the electron (to be gained from another element) decreases.
- The outer electron shell is further from the nucleus.
Test yourself on Halogens - Properties
How are halogens structured in their elemental form?
Why do halogens become less reactive as you go down the group?