**HIGHER TIER: Any reference to H2O, NH3, CH4, O2, N2 or CO2 bonding is higher tier.**
We can use dot and cross diagrams to show how a pair of electrons forms a covalent bond.
Here is the dot and cross diagram for oxygen (O2), a diatomic molecule. Notice the lone pairs of electrons and the two shared pairs of electrons.
Here are the dot and cross diagrams for some other common molecules.**
There are different kinds of covalent bonds:
The table below shows several molecules with double and triple covalent bonds.