Why Sc can't form MO oxides

Transition metals are elements which have incompletely filled d orbitals. Thus Sc is considered as transition element. As the ions the most common as well as stable oxidation state of  is Scandium (3+).Thus, Sc₂O₃ is the only known oxide.This is due to the presence of empty s and d orbital in this oxidation state with noble gas configuration. Hence monoxide of Sc is not known due to absence of existence of +2 oxidation of Sc.

Note : Electronic configuration of the Sc³⁺ ion, namely [Ar]3d⁰.This electronic configuration is a noble gas configuration which is more stable than +2 oxidation state of Sc.