Begin to explain some trends across a period of the periodic table.

As you move from group 1 across the periodic table to group 7.

1. The types of bonding change. Consider an element within group 1 - Lithium (Li). This exists as a metal, it has metallic bonding. This means there is a positive metal ion surrounded by a 'sea' of delocalised electrons. As lithium is from group 1, it will have a charge of +1. (Side task: consider why this is?) As you move across the period, towards group 7, you will find Oxygen (O). Oxygen exists as a diatomic molecule (you will find two oxygen atoms together O2). Here the bonding is different, there are covalent bonds between the two atoms. Oxygen choses to share electrons to fill its octet rather than donate / accept.