3. Mg → MgO → Mg(NO₃)₂ → Mg(OH)₂

\(2Mg+O_2\rightarrow2MgO\)

\(MgO+2HNO_3\rightarrow Mg(NO_3)_2+H_2O\)

\(Mg(NO_3)_2+2NaOH\rightarrow Mg(OH)_2\downarrow+2NaNO_3\)

Ответ: Mg → MgO → Mg(NO₃)₂ → Mg(OH)₂.