Why do the metal oxide having more oxidation number more acidic
Why do the metal oxide having more oxidation number more acidic
Generally, a compound of any element with higher oxidation state is more acidic than the compound of that element with lower oxidation state, viz., Fe3+ salts are more acidic than Fe2+, on the same line we may say that; oxide in the higher oxidation state of the element is more acidic than of a lower oxidation state. This is because, as the oxidation state increase the carge density of that atom also increases, consequently such atom strongly pulls the electron density towards itself from other specie that comes closer or in contact with it!
Now, question arises why pulling the electron density towards itself by the atom increase the acidity of that atom? Let us try to understand this by taking an example of reaction of such atom (in high and low oxidation state) with water. Fe2+ as well as Fe3+ in water forms hydrated ions viz., [Fe(H2O)6]2+ and [Fe(H2O)6]3+ respectively, these hydrated ions suffers hydrolysis of which former suffers less hydrolysis than later, as former is less acidic than later. Now, both the cations Fe2+ and Fe3+ are coordinated to six water molecules (ligands) but as the relative charge density of Fe3+ is more (higher charge and smaller size) than that of Fe2+ (lower charge and bigger size) the lone-pair of water molecules coordinated to Fe3+ will get more strongly pulled towards the metal ion, remember, that, it is the oxygen and not hydrogen of water molecule that is coordinated with the metal, so, this will cause a net drift of electron density from hydrogen to oxygen (of water molecule) making hydrogen atoms of coordinated molecule more positively charged, consequently, these hydrogen atoms may leave as H+ ions and thus can act as acid!
Generally, a compound of any element with higher oxidation state is more acidic than the compound of that element with lower oxidation state, viz., Fe3+ salts are more acidic than Fe2+, on the same line we may say that; oxide in the higher oxidation state of the element is more acidic than of a lower oxidation state. This is because, as the oxidation state increase the carge density of that atom also increases, consequently such atom strongly pulls the electron density towards itself from other specie that comes closer or in contact with it!
Now, question arises why pulling the electron density towards itself by the atom increase the acidity of that atom? Let us try to understand this by taking an example of reaction of such atom (in high and low oxidation state) with water. Fe2+ as well as Fe3+ in water forms hydrated ions viz., [Fe(H2O)6]2+ and [Fe(H2O)6]3+ respectively, these hydrated ions suffers hydrolysis of which former suffers less hydrolysis than later, as former is less acidic than later. Now, both the cations Fe2+ and Fe3+ are coordinated to six water molecules (ligands) but as the relative charge density of Fe3+ is more (higher charge and smaller size) than that of Fe2+ (lower charge and bigger size) the lone-pair of water molecules coordinated to Fe3+ will get more strongly pulled towards the metal ion, remember, that, it is the oxygen and not hydrogen of water molecule that is coordinated with the metal, so, this will cause a net drift of electron density from hydrogen to oxygen (of water molecule) making hydrogen atoms of coordinated molecule more positively charged, consequently, these hydrogen atoms may leave as H+ ions and thus can act as acid!
