The transition metals and their compounds have paramagnetic properties. This is due to the reason that ions of transition metals have unpaired electrons in (n-1)d orbitals. As the number of unpaired Sc to Mn, the paramagnetic character increases accodingly. From Mn onwards, this character decreases as electrons get paired up. The paramagnetic behaviour is expressed in terms of magnetic moment which is because of the spin of unpaired electron (n). It is given as Magnetic moment `= sqrt(n(n+2))B.M`
Majority of transition metal compounds are coloured both in solid state as well as in aqueous solution. due to d-d transition in which unpaired electrons from the lower energy d-orbitals are transferred to higher energy d-orbitals. The energy of this transition correspond to the radiation in visibe region. Thus, when white light falls on such a transition metal compound, some light energy corresponding to a particular colour is absorbed and one or more electrons are raised from lower energy set of orbitals to those of higher energy. With the absorption of radiations corresponding to specific colour from the white light, a colour known asd the complementary colour is observed or transmitted.
A compound of metal ion `M^(x+) (z = 24)` has a spin only magnetic moment of `sqrt(15)B.M.` The number of unpaired electrons in the metal ion of the compound are