Find the number of metal oxides which are decomposed on normal heating from the given oxides: Na2O, Al2O3, PbO, Ag2O, HgO

Metal oxides which are decomposed on normal heating are those that have low melting points, or, in other words, we can say that the compounds which are less reactive are decomposed on normal heating.2Ag2​O→4Ag+O2​ (at room temperature)HgO decomposes upon heating to give Hg and O2​ (oxygen gas) as follows :2HgO→2Hg+O2​Other oxides require very high temperatures to decompose and they do not decompose at normal temperature.Hence, only 2 metal oxides, from the given set of oxides, decompose on normal heating.