4.1.2.6 Group 7

Fl

Highly reactive poisonous yellow gas

Cl

Less reactive

Poisonous green gas

Br

Red, brown

Volatile, poisonous liquid

I

Dark grey solid

Can form poisonous purple vapours

Electronic structure of halogens

Seven electrons in outer energy level

Exist as diatomic molecule.

Do this by sharing electrons

Can form covalent bonds to form simple molecular structures

Trends of group 7

* melting and boiling point increase going down group
* Size increases going down group 7
* reactivity decreases

why reactivity decreases going down group 1

Because as you go down the group,

There is a greater distance between the outer energy level and the nucleus

therefore shielding by internal electrons

So the electrostatic force get weaker

making it harder for and electron to be gained

halogen and non-metals

Form a single covalent compound when they react with nonmetals

Halogen atoms can share electrons by a covalent bonding with other nonmetals, so it achieves a full outer shell

The compounds that form when halogens react with nonmetals, or have simple molecular structures

halogens and metals

They gain an electron from the metal atom (go from halogens → halides)

Displacement reactions

More reactive halogen taking place of a less reactive halogen from an aqueous solution of its salt

why elements get less reactive going down group 7

greater distance between the outer energy level and the nucleus

the outer energy level is shielded from the positive charge of the nucleus by internal electrons

so its harder to attract an electron to its outer energy level