Question

Identify the current trend given below: (Atomic No)
a) $ {\Delta ^ \circ }{\text{ of }}{\left[ {Cr{{\left( {{H_2}O} \right)}_6}} \right]^{2 + }} > {\left[ {Mo{{\left( {{H_2}O} \right)}_6}} \right]^{2 + }}{\text{ and }}{\Delta ^ \circ }{\text{ of }}{\left[ {Ti{{\left( {{H_2}O} \right)}_6}} \right]^{3 + }} > {\left[ {Ti{{\left( {{H_2}O} \right)}_6}} \right]^{2 + }}{\text{ }} $
b) $ {\Delta ^ \circ }{\text{ of }}{\left[ {Cr{{\left( {{H_2}O} \right)}_6}} \right]^{2 + }} > {\left[ {Mo{{\left( {{H_2}O} \right)}_6}} \right]^{2 + }}{\text{ and }}{\Delta ^ \circ }{\text{ of }}{\left[ {Ti{{\left( {{H_2}O} \right)}_6}} \right]^{3 + }} < {\left[ {Ti{{\left( {{H_2}O} \right)}_6}} \right]^{2 + }}{\text{ }} $

Answer 1

Hint: Crystal field theory is a model for bonding interaction Between ligand ands and transition metals. This theory was developed by considering energy changes of the following five degenerate articles.

Complete Step by step solution:
As the ligand will be closer to some of d orbitals a loss and farther away from others, this leads to degeneracy. The splitting of orbitals is affected by the following factors.
They include:
The nature of metal ions and it's oxidation are the arrangements of ligands around the metal ion.
The coordination number of metal ion for example tetrahedral
The nature of ligaments.
The most common type of complex is octahedral in which six ligands surround metal ions.
In $ \left[ {Cr({H_2}{0_6})} \right] $ ,chromium is surrounded by 6.H20 ligands and it is an octahedral complex.
In $ \left[ {Mo{{({H_2}O)}_6}} \right] $ the metal ion is Mo and it is also surrounded by 6 water molecules.
Crystal field energy is inversely proportional to size Hence crystal field energy of chromium is smaller in size. In $ {\left[ {Ti{{({H_2}0)}_6}} \right]^{^{3 + }}} $ oxidative state or charge on it is $ + 3 $ and in $ {\left[ {Ti{{({H_2}0)}_4}} \right]^{ + 2}} $ is $ + 2 $
Crystal field energy is directly proportional to charge hence $ {\left[ {Ti{{({H_2}0)}_6}} \right]^{^{3 + }}} $ with $ + 3 $ oxidation state has more energy.

Note:
Crystal field theory is also known as ligand field theory.
Ligands in coordination chemistry is a molecule which combines with the central atom to form a coordinate bond. When ligands bond with a metal they usually donate electrons. The bond formed by the metal and ligand can be covalent or ionic, example water, ammonia, cyanide.