3a4 Group I and Group VII

If you have 11 electrons to deal with (like sodium): 2,8,1
If you have 19 electrons (like potassium) to deal with: 2,8,8,1
The “1” in the outside shell is common to all of Group I.

The alkali metals (NOT alkaline) are all part of Group I.
They are fairly soft metals (can be cut with a knife)
They get softer as you go down the group.
The melting point decreases as you go down the group.
The reactivity increases as you go down the group.
They all react with water to give hydrogen and the metal hydroxide.

Similarly, if you have 9 electrons to deal with (like fluorine): 2,7
And if you have 17 electrons (like chlorine) to deal with: 2,8,7
The “7” in the outside shell is common to all of Group VII.

The halogens are all part of Group VII.
They are all diatomic molecules (two atoms per molecule)
The melting point increases as you go down the group.
The halogens react with many metals to form a halide salt.
The reactivity decreases as you go down the group.

For both the alkali metals and the halogens you need to be able to describe experiments to demonstrate their reactivity trends.