An unidentified metal M reacts with an unidentified halogen X to form a compound MX2. When heated, the compound decomposes by the reaction: When 1.12 g of MX2 is heated, 0.720 g of MX is obtained, along with 56.0 mL of X2 gas. Under the conditions used, 1.00 mol of the gas has a volume of 22.41 L. (a) What is the atomic weight and identity of the halogen X?