Question

Total number of unpaired electrons in ${Co^{3+}}$ ( $Atomic\,number = 27$ ):

Answer 1

To calculate the number of unpaired electrons of the given ion, we have to write and check the electronic configuration of this atom. Cobalt is a transition metal of the $3d -$ series. It is a silver-grey metal that is found in the earth’s crust.

Complete Step-by-step Answer:
Elements from $Sc(scandium)$ to $Zn(zinc)$ come in the $3d -$ series of the D block elements. These elements can be found from the ${3^{rd}}$ group to the ${12^{th}}$ group of the modern periodic table. Now we will write the electronic configuration of this element. The transition metals have a d-subshell that is partially filled with electrons. The compounds and ions of the d-block are colored due to the $d - d$ transition shown by electrons. Many types of ligands bind themselves with these elements and form a coordination compound. These elements have great use as catalysts in several reactions and mechanisms. They also exhibit a wide range of oxidation states and due to this, they form stable complexes.
Now we will calculate the number of unpaired electrons in $C{o^{3 + }}$ ion with the help of electronic configuration of cobalt. Its atomic number is $27$ . Its electronic configuration will be $[Ar]\,3{d^7}\,4{s^2}$ . It has $7$ electrons in its d-orbital. After forming $C{o^{3 + }}$ ion it will lose $3$ electrons, two will be from $s - orbital$ and $$ 1 $$ will be from the $d$ orbital. Now, their arrangement will be like $\matrix { \uparrow \downarrow } \& { \uparrow } \& {\uparrow } \& { \uparrow \,\,\,\, \uparrow }$ . Hence it will have $4$ unpaired electrons. Therefore we can say that the total number of unpaired electrons in $C{o^{3 + }}$ is $4$ .

Note:
Elements of the $3d -$ series show great properties of metals like ductility, malleability, and lustre. They also show high melting and boiling points. Due to their small size, they have high ionization enthalpies.