The basic character of the transition metal monoxides follows the...

As we move from left side to right side in the first transition series atomic number of elements increases and no. of electrons also increases. Size of elements on moving left to right decreases because effective nuclear charge of nucleus on the outermost shell electron increases. It means electronegativity of atoms increases from left to right, then the power of donation of electrons decreases which means the basicity of that element decreases. Caution Students get confused on the order of size of elements in the series, because order of size of elements is not regular in the periods and groups. In periods of increasing atomic number size decreases and on the groups with the increase of atomic number size also increases.