Final answer:
In the formula XSO3, 'X' could be either Calcium (Ca) or Barium (Ba) as both these elements have a charge of +2, which can neutralize the -2 charge from SO3.
Step-by-step explanation:
In the given formula XSO3, the 'X' represents an unidentified element that makes a compound with sulphite (SO3). Each element in the Periodic table has a specific valency, which is the combining capacity of an element. Sulfites (SO3) have a charge of -2. Thus, 'X' can be any element that has a +2 charge to neutralize the -2 charge from SO3. From given options, both Calcium (Ca) and Barium (Ba) have a charge of +2. So, 'X' in the given formula could be either Calcium (Ca) or Barium (Ba).
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