Elements X and Y are both in period three. If the chloride of X is added to water, it reacts, and a solution with $\text{pH }2$ is formed. If the chloride of Y is added to water, it dissolves, and a solution with $\text{pH }7$ is formed. Which statement accounts for these observations?
- ABoth chlorides hydrolyse in water.
- BX is phosphorus and Y is aluminium.
- CX is silicon and Y is sodium.
- DX is sodium and Y is phosphorus.