Chapter 8: The D-block and F-block Elements

Ans: (B) 26

Positive oxidation states indicate the loss of electrons from the atom. If X is in +3 oxidation state, then three electrons have been removed from it. Find the atomic number of the parent atom, we will add three in the given electronic number. i.e.

${{\text{X}}^{{\text{3 + }}}}{\text{(Z = 23)  =  }}\left[ {{\text{Ar}}} \right]{\text{ 3}}{{\text{d}}^{\text{5}}}$

${\text{X  =  23  +  3  =  26}}$ 

Ans: (A) \[Cu\left( {II} \right)\] is more stable .

Electronic configuration of \[{\text{Cu}}\]is \[\left[ {{\text{Ar}}} \right]{\text{ 3}}{{\text{d}}^{{\text{10}}}}{\text{ 4}}{{\text{s}}^{\text{1}}}\]

\[{\text{Cu}}\left( {\text{I}} \right)\] - \[\left[ {{\text{Ar}}} \right]{\text{ 3}}{{\text{d}}^{{\text{10}}}}{\text{ 4}}{{\text{s}}^0}\]

\[{\text{Cu}}\left( {{\text{II}}} \right)\]- \[\left[ {{\text{Ar}}} \right]{\text{ 3}}{{\text{d}}^9}{\text{ 4}}{{\text{s}}^0}\]

Despite the fact that\[{\text{Cu}}\left( {\text{I}} \right)\]  has fully filled 3d-orbital but \[{\text{Cu}}\left( {{\text{II}}} \right)\] is more stable than \[{\text{Cu}}\left( {\text{I}} \right)\] due to the greater effective nuclear charge of \[{\text{Cu}}\left( {{\text{II}}} \right)\] as nucleus has to hold 17 electrons rather than 18 electrons like in \[{\text{Cu}}\left( {\text{I}} \right)\].

Ans: (D) Cu

Density is mass by volume. As we move from left to right for a long period, the atomic radii decrease. Hence, volume decreases. Also, an increase in atomic masses is observed. 

So overall the density increases out of the above option from iron to copper, copper will have the highest density.

Ans: (B) $Cu{F_2} $

$\left( {\text{A}} \right){\text{ A}}{{\text{g}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}{\text{ (A}}{{\text{g}}^{\text{ + }}}) \to {\text{ 5}}{{\text{d}}^{{\text{10}}}}{\text{ 6}}{{\text{s}}^{\text{0}}}$

$\left( {\text{B}} \right){\text{ Cu}}{{\text{F}}_{\text{2}}}{\text{  (C}}{{\text{u}}^{{\text{2 + }}}}) \to {\text{ 3}}{{\text{d}}^9}{\text{ 4}}{{\text{s}}^{\text{0}}}$

$\left( {\text{C}} \right){\text{ Zn}}{{\text{F}}_{\text{2}}}{\text{ (Z}}{{\text{n}}^{{\text{2 + }}}}{\text{)}} \to {\text{ 3}}{{\text{d}}^{{\text{10}}}}{\text{ 4}}{{\text{s}}^{\text{0}}}$

$\left( {\text{D}} \right){\text{ C}}{{\text{u}}_{\text{2}}}{\text{C}}{{\text{l}}_{\text{2}}}{\text{ (C}}{{\text{u}}^{\text{ + }}}) \to {\text{ 3}}{{\text{d}}^{{\text{10}}}}{\text{ 6}}{{\text{s}}^{\text{0}}}$

Unpaired electrons present in any compound impart colour to the salt of transition metal. Only \[{\text{Cu}}{{\text{F}}_{\text{2}}}\] has unpaired electrons in its \[{\text{3d}}\]orbital that’s why it is white coloured in its solid-state while rest of the salts are colourless.

Ans: (A)  $M{n_2}{O_7} $

${\text{2KMn}}{{\text{O}}_{\text{4}}}{\text{  +  2}}{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}{\text{(conc}}{\text{.) }} \to {\text{ M}}{{\text{n}}_{\text{2}}}{{\text{O}}_{\text{7}}}{\text{    +    2KHS}}{{\text{O}}_{\text{4}}}{\text{  +  }}{{\text{H}}_{\text{2}}}{\text{O}}$

Manganese heptoxide is an acid anhydride of permanganic acid \[\left( {{\text{ HMn}}{{\text{O}}_{\text{4}}}} \right)\]. It is a dangerous oxidiser, volatile and highly reactive liquid.

Ans: (B) $3{d^5} $

Magnetic moment of an electron/dipole moment is caused by its intrinsic properties of spin and electric charge. It depends upon the number of unpaired electrons in its valence shell. The more the number of unpaired electrons, the greater will be the value of magnetic moment.

${\text{3}}{{\text{d}}^{\text{7}}}{\text{  =  3 unpaired electrons }}$

${\text{3}}{{\text{d}}^{\text{5}}}{\text{  =  5 unpaired electrons}}$

${\text{3}}{{\text{d}}^{\text{8}}}{\text{  =  2 unpaired electrons }}$

${\text{3}}{{\text{d}}^{\text{2}}}{\text{  =   2 unpaired electrons}}$ 

Out of all, \[{\text{3}}{{\text{d}}^{\text{5}}}\] has five unpaired electrons that is maximum and hence it has the highest magnetic moment.

Ans: (B) +3

Out of all +3 is the most common oxidation state for all the lanthanide elements.

Ans: (A)i,ii

Disproportionation/redox reaction is a reaction in which one compound is oxidised as well as reduced at the same time.

$\left( {\text{A}} \right){\text{ C}}{{\text{u}}^{\text{ + }}}{\text{ }} \to {\text{ C}}{{\text{u}}^{{\text{2 + }}}}{\text{  +    Cu }}$

${\text{        ( + 1)       ( + 2)        (0) }}$

$\left( {\text{B}} \right){\text{ 3Mn}}{{\text{O}}^{{\text{4--}}}}{\text{  +  4}}{{\text{H}}^{\text{ + }}}{\text{ }} \to {\text{ 2Mn}}{{\text{O}}_{\text{4}}}^{\text{--}}{\text{  +  Mn}}{{\text{O}}_{\text{2}}}{\text{  +  2}}{{\text{H}}_{\text{2}}}{\text{O }}$

${\text{         ( + 6)                          ( + 7)           ( + 4)}}$ 

Ans: (D)\[M{n^{2 + }}\] acts as auto catalyst

\[{\text{M}}{{\text{n}}^{{\text{2 + }}}}\] formed in the reaction acts as an autocatalyst. Auto catalyst is a compound that is one of the products that are formed in the reaction itself catalyses the reaction.

Reaction: \[{\text{2Mn}}{{\text{O}}^{{\text{4 - }}}}{\text{  +  16}}{{\text{H}}^{\text{ + }}}{\text{ +  5}}{{\text{C}}_{\text{2}}}{{\text{O}}_{\text{4}}}^{{\text{2 - }}} \to {\text{ 2M}}{{\text{n}}^{{\text{2 + }}}}{\text{  +  10C}}{{\text{O}}_{\text{2}}}{\text{  +  8H2O}}\]

Ans: (C) $Tm $

In the periodic table, actinides lie from atomic number 90 to 103. 

Thulium is not an actinide; it is a lanthanide.