Is it possible for two different compounds to be made from the exact same two elements? why or why not? with a limited number of elements (less than 120 are known), does this mean we also have a small number of compounds or do we have a large number of compounds in this world?

Yes, it is possible to combine the same two elements to form two different compounds. An example is carbon dioxide CO2 and carbon monoxide CO. This is because two elements can form different types of bond and end up with different compounds.

There is a limited number of elements but a large number of compounds because of the above reason.

We have a large number of compounds in this world so that implies it is possible for two different compounds to be made from the exact same two elements. Hydrocarbons are compounds made of Hydrogen and Carbon only and there are many different hydrocarbons; such as methane (CH4) and ethane (C2H6).

the formula would be mgso4

mgso[subscript]4