Why is Cu+ diamagnetic while Cu2+ is paramagnetic?

by BY P GHOSH on September 22, 2020 in INORGANIC

Why is Cu+ diamagnetic while Cu2+ is paramagnetic?

The diamagnetic and paramagnetic character of a substance depends on the number of odd electron present in that substance. The diamagnetic and paramagnetic character of Cu+ and Cu+ are discussed below.

Now, depending upon the hybridization, there are two types of possible structure of Cu+ and Cu2+ ion are formed with co-ordinationnumber 4.

If the complex ion involves ‘sp3’ hybridization, it would have tetrahedral structure. Again, if the complex involves ‘dsp2’ hybridization, it would have square planar structure.

According to Hund’s rule the outer electronic configuration of Cu+ ion is [Ar] 3d¹⁰ that is Cu⁺ ion is 3d¹⁰ systems. That is, 3d orbital of Cu+ ion is completely fulfilled but outer 4s orbital is vacant.

Why is Cu+ diamagnetic while Cu2+ is paramagnetic?

Hence according to valence bond theory the outer ‘4s’ orbital of cu+ ion is combined with the vacant three 4p orbital and form energetically equivalent four hybridized orbitals.

They are called sp3 hybridized orbitals. Now, four similar or dissimilar ligands are attached with these four hybridized orbitals through the formation of four co-ordinate bond.

As a result, Cu+ ion forms tetrahedral molecule involving ‘sp3’ hybridization. The outer electronic configuration of Cu⁺ion and its hybridization are shown below.

From the above electronic configuration of Cu+ ion, it has been found that it has no unpaired electrons. Since the Cu+ ion has no unpaired electrons, hence it is diamagnetic.

On the other hand, Cu²⁺ions are 3d⁹ system. According to Hund’s rule, the outer electronic configuration of Cu²⁺ion is [Ar] 3d⁹system.

From the above electronic configuration of Cu²⁺ion, it has been found that four d-orbitals of 3d-subshell is occupied by paired electrons and rest of the 3d-orbital contained single electron.

Now in the excited state the single electron of 3d_x2-y2 orbital absorbs energy and shifted to vacant 4Pz orbital. As a result of this, the inner 3d_x2-y2 orbital become vacant.

Under this condition, the vacant orbital of inner 3d-orbital is attached with the outer one 4s and 4p-orbitals, resulting in the formation of four energetically equivalent orbitals involving dsp2 hybridization.

Now, these four energetically equivalent vacant orbitals are chemically attached with four ligands through the formation of ligand-metal co-ordinate bond involving square planar structure molecule.

Under this condition, Cu²⁺ion have one unpaired 4Pz electron. Hence Cu²⁺ion show paramagnetic properties.

The outer electronic configuration of Cu²⁺ion and its hybridization are shown below.