An element X reacts with `H_(2)` gas at `200^(@)C` to form compound Y. when Y is heated to a higher temperature, it decomposes to element X and `H_(2)` gas in the ratio of 559 ml of `H_(2)` (measured at STP) for 1.00 g of X reacted. X also combines with `Cl_(2)` to form a compound Z which contains 63.89 peerrcent mass of chlorine. identify X, Y and Z.
