Y and Z are both elements in Period 3. If the chloride of Y is put into water, it reacts to form a solution with pH $2$. If the chloride of Z is put into water, it dissolves and gives a solution with pH $7$. Which statement accounts for these observations?
- ABoth chlorides hydrolyse in water.
- BY is magnesium and Z is sodium.
- CY is phosphorus and Z is aluminium.
- DY is silicon and Z is sodium.