KEAM 2011 Physics and Chemistry Paper

O2 molecule is paramagnetic and the presence of two unpaired electrons in the

*

π

(2px) or

*

π

(2py) molecular orbitals accounts for its paramagnetic nature. Similary in CrO2,Fe3O4 and ZnFe2O4, the d -orbitals of transition elements are not ful-filled and have unpaired electrons and hence, are paramagnetic. Whereas, H2O is diamagnetic because of the presence of all paired electrons and hence repelled by magnetic field.