Final answer:
Upon thermal decomposition, metal hydroxides typically release metal oxides and water, while metal carbonates generally release metal oxides and carbon dioxide gas. Exceptions exist, such as mercury(II) oxide which decomposes into mercury metal and oxygen gas, and alkali metals which form oxides through different methods.
Step-by-step explanation:
Upon thermal decomposition, many metal oxides release different substances depending on the specific metal oxide involved. For instance, metal hydroxides, upon heating, typically decompose to yield metal oxides and water. An example is the decomposition of sodium hydroxide to produce sodium oxide and water.
Similarly, metal carbonates decompose into a metal oxide and carbon dioxide gas; for example, calcium carbonate decomposes to form calcium oxide and carbon dioxide. Exceptions to these general rules include mercury(II) oxide, which decomposes into mercury metal and oxygen gas when heated. It is important also to consider the reactions of alkali metals.
These metals tend to form stable salts that do not decompose easily, leading to the formation of alkali metal oxides through oxidation-reduction reactions when their nitrates or hydroxides are heated with the metals. Additionally, when the metals of groups 1 and 2 are burned in air, they might react with nitrogen and form a mixture of oxides and ionic nitrides, peroxides, or superoxides.