COVALENT COMPOUNDS
The same rule that applies to diatomic elements can also apply to covalent compounds:
e.g. H-Cl (hydrogen chloride)
H
H
Cl
+
Cl
Here we can see that:



Hydrogen has a valency of 1: can form 1 bond
Chlorine has a valency of 1: can form 1 bond
So they will form a single ionic bond.
Another useful example to use is H2O:
H
+
H
+
O
H
O
Here we see that:



Hydrogen has a valency of 1: each can form 1 bond
Oxygen has a valency of 2: can form 2 bonds
So the oxygen makes a single covalent bond to each hydrogen.
H