Question

Explain the given reasons:
(a)- Transition metals and many of their compounds show paramagnetic behavior.
(b)- The enthalpies of the atomization of the transition metals are high.
(c)- The transition metals generally form colored compounds.
(d)- Transition metals and their many compounds act as a good catalyst.

Answer 1

Hint: If unpaired electrons are present in the compound then it shows paramagnetic behavior. Colored ions are formed due to the presence of unfilled d-subshell. The presence of unpaired electrons in the incomplete d-subshell helps to act as a good catalyst.

Complete answer:
(a)- Transition metals and many of their compounds show paramagnetic behavior.
Paramagnetism is a property which is shown by the elements having unpaired electrons. In the case of transition metals, as they contain unpaired electrons in the (n-1) d-orbitals, most of the transition metal ions and their compounds are paramagnetic. As the number of unpaired electrons increases from one to five, the paramagnetic character increases.
(b)- The enthalpies of the atomization of the transition metals are high.
There are a large number of valence electrons and have a high effective nuclear charge in the transition metals. Due to which they form a strong metallic bond and these bonds have high enthalpies of atomization.
(c)- The transition metals generally form colored compounds.
Color is due to the presence of incomplete d-subshell. Further, when the anion or the ligands approach the transition metal ions, their d-orbitals do not remain degenerated. They split into two sets, one consisting of lower energy orbitals (\[{{\text{t}}_{\text{2g}}}\text{which includes }{{\text{d}}_{\text{xy}}}\text{,}{{\text{d}}_{\text{yz}}}\text{,and }{{\text{d}}_{\text{zx}}}\]) and the other consisting of higher energy orbitals (\[{{e}_{\text{g}}}\text{which includes }{{\text{d}}_{{{\text{x}}^{2}}-{{y}^{2}}}}\text{,and }{{\text{d}}_{{{\text{z}}^{2}}}}\]). This is called crystal field splitting.

Thus, the electron can jump from lower energy d-orbital to higher energy d-orbital. The required amount of energy to do this is obtained by absorption of light of a particular wavelength in the region of visible light. The transition metal ion has the property to absorb such radiations from the visible light and appears colored due to the emission of the remainder as colored light.
(d)- Transition metals and their many compounds act as a good catalyst.
The catalytic property of transition metals is due to the presence of unpaired electrons in their incomplete d-orbitals and hence possesses the capacity to absorb and re-emit a wide range of energies. It is also due to the varying oxidation state of transition metal ions.

Note: Transition metal ions are colored in both solid and aqueous state. The elements from transition metals that are used as catalysts are vanadium, platinum, iron, cobalt, nickel, etc.