The d and f Block Elements

 $\left[Co{\left(H_{2}O\right)}_6\right]C{l}_2\Rightarrow C{o}^{2+}\Rightarrow 3d^7\Rightarrow {t_{2g}}^{5}e{g}^2$

Number of unpaired electrons = 3

$\left[Cr{\left(H_{2}O\right)}_6\right]C{l}_3\Rightarrow C{r}^{3+}\Rightarrow 3d^3\Rightarrow {t_{2g}}^{3}e{g}^0$

Number of unpaired electrons = 3

$\stackrel{+4}{Mn{F}_4}$ $\stackrel{+3}{Mn{F}_3}$

E.C = [Ar] 3d³                    [Ar]3d⁴

$\begin{array}{cc}\hfill \stackrel{+2}{Mn{F}_2}\hfill & \hfill \left[Ar\right]3d^5\hfill \end{array}\left[\begin{array}{l}{E}_{M{n}^{3+}|M{n}^{2+}}^0=1.57V\\ E_{M{n}^{4+}|M{n}^{2+}}^0=1.27V\end{array}\right]$

 $\stackrel{+7}{M}n{O}_4^{-}+8H^{+}+5e\to \stackrel{+2}{M}{n}^{2+}+4H_{2}O$ change in oxidation number of Mn = 7 – 2 = 5

Kindly go through the solution 
$2Mn{O}_4^{-}+5H_2{O}_2+6H^{+}\to 2M{n}^{2+}+8H_{2}O+5O_2$

 No. of electron = 62 – 2 = 60

$68^{E{r}^{+3}}$ No. of electron = 68 – 3 = 65

$70^{Y{b}^{+2}}$ No. of electron = 70 – 2 = 68

$71^{Lu+3}$ No. of electron = 71 – 3 = 68

$65^{T{b}^{+4}}$ No. of electron = 65 – 4 = 61

$63^{E{u}^{+2}}$ No. of electron = 63 – 2 = 61

$65^{T{b}^{+2}}$ No. of electron = 65 – 2 = 63

$69^{T{m}^{+4}}$ No. of electron = 69 – 4 = 65

Valence shell electronic configuration of Eu in +2 O.S is,

$E{u}^{2+}=6s^{0}4f^7$                

It has half filled f-sub shell and stable.

Following is the reaction of KMnO4 in basic medium with thiosulphate anion.

$\stackrel{+7}{8Mn{O}_4^{-}}+3S_2{O}_3^{--}+H_{2}O\to \stackrel{+4}{8Mn{O}_{2|}}+6S{O}_4^{--}+2O{H}^{-}$

Change = 7 – 4 = 3

  $S{c}^{3+}-3d^0$ electron in last subshell

$Z{n}^{2+}-3d^{10}$ electron in last subshell

$T{i}^{4+}-3d^0$ electron in last subshell

$C{u}^{2+}-3d^9$ electron in last subshell

$V^{2+}-3d^3$ electron in last subshell

$T{i}^{3+}-3d^1$ electron in last subshell

$M{n}^{2+}-3d^5$ electron in last subshell

Sol. (i) Foam - Froth (e)

(ii) Gel - Jellies (c)
(iii) Aerosol - smoke (a)
(iv) Emulsion - milk (f)