question_answer

Which of the following statements is INCORRECT?

A) \[{{K}_{2}}[NiC{{l}_{4}}]\]exists while \[{{K}_{2}}[PtC{{l}_{4}}]\] is unknown.

B) \[{{K}_{2}}[NiC{{l}_{6}}]\] exists while \[{{K}_{2}}[PtC{{l}_{6}}]\] is unknown.

C)  \[I{{E}_{3}}\]of \[Mn\] is higher than that of\[Fe\].

D)  Transition metal Scandium \[(Sc,\,Z=21)\] does not show variable oxidation state.

Correct Answer: B

Solution :

[b] (1) CORRECT statement:-It is reverse. IE explains about relative stabilities of various oxidation state. For example \[N{{i}^{2+}}\] compounds are more stable than \[P{{t}^{2+}}\]compounds, e.g.,            

		\[I{{E}_{1}}+I{{E}_{2}}(kJ\,mo{{l}^{-1}})\]
\[Ni\]	\[2.49\]	Smaller the \[(I{{E}_{1}}+I{{E}_{2}})\]of the metal more stable is its compound. \[\therefore \] Stability \[N{{i}^{2+}}>P{{t}^{2+}}\]
\[Pt\]

Due to imperfect shielding effect of 4/-orbitals. This shielding effect increases the attraction between nucleus and outermost electron and hence \[(I{{E}_{1}}+I{{E}_{2}})\] of Pt is more. (2) \[(I{{E}_{1}}+I{{E}_{2}}+I{{E}_{3}}+I{{E}_{4}})\]is lower for Pt. High \[(I{{E}_{3}}+I{{E}_{4}})\] value for \[Ni\]is due to very small size of\[N{{i}^{3+}}\] and \[N{{i}^{4+}}\] in comparison to \[P{{t}^{3+}}\] and \[P{{t}^{4+}}\] Hence stability of \[P{{t}^{4+}}>N{{i}^{4+}}\]

	\[I{{E}_{3}}+I{{E}_{4}}\] \[(kJmo{{l}^{-1}})\]	\[I{{E}_{1}}+I{{E}_{2}}+I{{E}_{3}}+I{{E}_{4}}\] \[(kJ\,mo{{l}^{-1}})\]
\[Ni\]	\[8.80\]	\[11.29\]
\[Pt\]	\[6.70\]	\[9.36\]

(3) \[Mn(Z=25):3{{d}^{5}}4{{s}^{2}};\] \[Fe(Z=26):3{{d}^{6}}4{{s}^{2}}\] \[M{{n}^{2+}}:3{{d}^{5}}\]                   \[F{{e}^{2+}}:3{{d}^{6}}\] After the removal of second electron, \[M{{n}^{2+}}\] and \[F{{e}^{2+}}\]acquire a configuration of \[3{{d}^{6}}\] and \[3{{d}^{5}}\]respectively. Thus to remove an electron from \[3{{d}^{5}}\]if is more difficult than from \[3{{d}^{6}}\].Hence \[I{{E}_{3}}\]of \[Mn>I{{E}_{3}}\] of\[Fe\]. 4. Scandium (Sc) \[(Z=21);\] \[3{{d}^{1}}4{{s}^{2}}\] \[S{{c}^{2+}}:3{{d}^{1}}\Rightarrow \] Highly unstable, does not exist. \[S{{c}^{3+}}:3{{d}^{0}}\Rightarrow \]Noble gas configuration, stable and exis: Therefore \[Sc\]shows only \[+3\] Oxidation state