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Question : 24
Total: 26
(a) Account for the following:
(i) Transition metals form large number of complex compounds.
(ii) The lowest oxide of transition metal is basic whereas the highest oxide is amphoteric or acidic.
(iii)E ∘ Mn 3 + ∕ Mn 2 + ( + 1.57 V ) Cr 3 + ∕ Cr 2 +
(b) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.
OR
(a) (i) How is the variability in oxidation states of transition metals different from that of the p-block elements ?
(ii) Out ofCu + Cu 2 +
(iii) Orange colour ofCr 2 O 7 2 −
(b) Chemistry of actinoids is complicated as compared to lanthanoids. Give two reasons.
(i) Transition metals form large number of complex compounds.
(ii) The lowest oxide of transition metal is basic whereas the highest oxide is amphoteric or acidic.
(iii)
(b) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.
OR
(a) (i) How is the variability in oxidation states of transition metals different from that of the p-block elements ?
(ii) Out of
(iii) Orange colour of
(b) Chemistry of actinoids is complicated as compared to lanthanoids. Give two reasons.
Solution:
(a) (i) Transition metals form large number of complexes due to following reasons:
a. Small size of metal ion
b. High charge density
c. Availability of emptyd
(ii) In the lowest oxides of transition metals, the metal atom has low oxidation state. This means some of the valence electrons of metal atom are not involved in the bonding. So, these electrons are not available for donation. Hence, they are basic in nature.
However, in the higher oxides of transition metals, the metal atom has high oxidation state. This means all of the valence electrons of metal atom are involved in the bonding.
So, these electrons are not available for donation. Also, these metal ions have high effective nuclear charge. As a result, they can accept electrons. Hence, they are acidic in nature.
(iii)Mn 2 + d 5 Mn 3 + d 4 d 4 d 5 ∆ G E ∘
WhileCr 3 + d 3 ( t 2 g 3 ) Cr 2 + d 4 ( t 2 3 ) Cr 3 + Cr 2 + E ∘
(b) Similarities between lanthanoid and actinoid:
(i) They have prominent oxidation states of +3 .
(ii) They are electropositive.
(iii) They show magnetic properties
Differences between lanthanoid and actinoid :
(i) Lanthanoids are involved in filling of 4f-orbitals, actinoids are involved in filling of 5 f-orbitals.
(ii) Binding energy of4 f 5 f
OR
(a) (i) Variable oxidation states shown by transition element can differ by one unit while oxidation state shown by nontransition elements differ by two units (sometimes due to inert pair effect).
For example, oxidation state of
S = − 2 , − 4 , − 6
Oxidation state ofCo = + 2 , + 3 , + 4
(ii)Cu + Cu 2 + Cu + Cu 2 + Cu 2 + Cu 2 + Cu +
(iii) The change in colour is due to the formation of chromate ion.
Cr 2 O 7 2 − + H 2 O → 2 Cr 2 O 4 2 − + 2 H +
(b) The reasons for this are as follows :
(i) Actinoids display a large number of oxidation states while lanthanoids primarily show only three oxidation states.
(ii) Actinoids are radioactive in nature.
a. Small size of metal ion
b. High charge density
c. Availability of empty
(ii) In the lowest oxides of transition metals, the metal atom has low oxidation state. This means some of the valence electrons of metal atom are not involved in the bonding. So, these electrons are not available for donation. Hence, they are basic in nature.
However, in the higher oxides of transition metals, the metal atom has high oxidation state. This means all of the valence electrons of metal atom are involved in the bonding.
So, these electrons are not available for donation. Also, these metal ions have high effective nuclear charge. As a result, they can accept electrons. Hence, they are acidic in nature.
(iii)
While
(b) Similarities between lanthanoid and actinoid:
(i) They have prominent oxidation states of +3 .
(ii) They are electropositive.
(iii) They show magnetic properties
Differences between lanthanoid and actinoid :
(i) Lanthanoids are involved in filling of 4f-orbitals, actinoids are involved in filling of 5 f-orbitals.
(ii) Binding energy of
OR
(a) (i) Variable oxidation states shown by transition element can differ by one unit while oxidation state shown by nontransition elements differ by two units (sometimes due to inert pair effect).
For example, oxidation state of
Oxidation state of
(ii)
(iii) The change in colour is due to the formation of chromate ion.
(b) The reasons for this are as follows :
(i) Actinoids display a large number of oxidation states while lanthanoids primarily show only three oxidation states.
(ii) Actinoids are radioactive in nature.
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