Question
Given below are two statements:
Statement-I : Among $Zn,Mn,Sc$ and Cu , the energy required to remove the third valence electron is highest for Zn and lowest for Sc .
Statement-II : The correct order of the following complexes in terms of CFSE is
$\left\lbrack Co\left( H_{2}O \right)_{6} \right\rbrack^{2 +} < \left\lbrack Co\left( H_{2}O \right)_{6} \right\rbrack^{3 +} < \left\lbrack Co(en)_{3} \right\rbrack^{3 +}$.
In the light of the above statements, choose the correct answer from the options given below :
Options
Solution
Sol. [Key Concept: 3rd IE is highest for Zn and lowest for Sc; CFSE rises with ligand strength and metal charge.]
Statement I
Sc 2393 (IE $(kJ/mol)$),
Mn 3260 (IE $(kJ/mol)$),
Cu 3556 (IE $(kJ/mol)$),
Zn 3837 (IE $(kJ/mol)$),
$Sc < Mn < Cu < Zn\left( 3^{\text{rd}\text{~}} \right.\ $ IE $)$
Statement II
CFSE ⇒ SFL > WFL
$$\left( en > H_{2}O \right)$$
CFSE $\propto$ Charge on metal
$${Co}^{+ 2} < {Co}^{+ 3}$$
$$\left\lbrack Co\left( H_{2}O \right)_{6} \right\rbrack^{2 +} < \left\lbrack Co\left( H_{2}O \right)_{6} \right\rbrack^{3 +} < \left\lbrack Co(en)_{3} \right\rbrack^{3 +} $$
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