Group 7A elements, also known as halogens, include fluorine (F), chlorine (Cl), and bromine (Br). Halogens have their own unique properties:
- They have seven valence electrons in their outermost shell.
- They are highly reactive, particularly with alkali metals and alkaline earth metals.
- They exist in different states: fluorine and chlorine as gases, bromine as a liquid, and iodine as a solid.
Halogens need one more electron to complete their valence shell to become stable. When they gain an electron, they form -1 ions. For example:
- Fluorine (F) gains one electron to form F鈦
- Chlorine (Cl) gains one electron to form Cl鈦
- Bromine (Br) gains one electron to form Br鈦
These gained electrons make the ions negatively charged, or anions. The reactivity of halogens decreases as you move down the group. This means fluorine (F) is more reactive than chlorine (Cl), which is more reactive than bromine (Br).