Question

Answer the following question: Among the divalent cations in the first series of transition elements, manganese exhibits the maximum paramagnetism.

Answer 1

Hint: The paramagnetic species are those that have unpaired electrons. The paramagnetic character is directly proportional to the number of unpaired electrons. Thus, higher is the number of unpaired electrons, higher will be the paramagnetic character.

Complete step by step solution:
First, let us see what is paramagnetism.
The paramagnetism may be defined as the presence of unpaired electrons in the atoms of the element. As these unpaired electrons can be excited and even emitted, thus the paramagnetic species are coloured in nature.
The transition elements include all the d - block elements.
The paramagnetic character is directly proportional to the number of unpaired electrons.
If we see the first transition series, it involves the filling of 3d orbitals. Initially, all the electrons remain unpaired and when all the orbitals are filled with a single electron each, then the pairing starts. The filling can be written as
Sc (21) = $3{d^1}4{s^2}$
Ti (22) = $3{d^2}4{s^2}$
V (23) = $3{d^3}4{s^2}$
Cr (24) = $3{d^5}4{s^1}$
Mn (25) = $3{d^5}4{s^2}$
Iron (26) = $3{d^6}4{s^2}$
Further, the word divalent cations mean that the elements have donated two electrons. The first series of transition elements include the metals that can easily donate the electrons and become stable.
After the donation of two electrons, the electronic configurations are-
Sc (21) = $3{d^1}4{s^0}$
Ti (22) = $3{d^2}4{s^0}$
V (23) = $3{d^3}4{s^0}$
Cr (24) = $3{d^4}4{s^0}$
Mn (25) = $3{d^5}4{s^0}$
Iron (26) = $3{d^6}4{s^0}$
So, on observing the electronic configurations, we see that after Mn, the pairing of electrons starts. Thus, the number of unpaired electrons will start decreasing. And after the donation of two electrons, the Mn has the highest number of unpaired electrons. So, the Mn will have the highest paramagnetic character.

Note: The species that have all the atoms paired up are called diamagnetic species. These are usually colourless in nature. The d- block elements are called transition elements because these show a transition of various characters from metal-containing s - block to non-metal containing p - block. There is a gradual change. So the term transition is employed.