ABSTRACT
When considering basic properties of the oxides we must stress the fact that oxygen atoms, when linked with two single covalent bonds or with one double bond, still possess two unshared electron pairs enabling them to act as donors, i. e., to exercise the function of a base. The electron-donating ability of oxygen obviously increases with increasing negative charge, but Sanderson points out that the donating ability of oxygen is stronger when the oxygen atom is attached by single rather than multiple bonds. He believes that this effect is the result of a greater localization of unshared electron pairs in the former case than in the latter. This explanation would be equivalent to the assumption that the localization is greater when unbonding electron pairs occupy sp3 hybrid orbitals than when they occupy sp2 hybrids. This explanation seems rather doubtful from the point of view of quantum chemistry as the spn hybrids are considered to exhibit higher bonding ability (and hence the higher concentration of electron density) when the participation of s orbitals is higher [12]. As shown by the data in Table 1.3, oxygen atoms in oxides which are known to be very strongly basic, such as the oxides of alkali metals, bear the highest negative partial charge. The amphoteric oxides BeO, A1203, and H20 occupy a central position in the series of oxides ordered according to the decreasing negative charge on oxygen. The donating ability of oxygen and the tendency of the other atom to accept an electron pair are comparable in these compounds and, depending on conditions, the compounds may act either as a weak base or a weak acid.
