Write down the electronic configuration of Co 2 +

Co 2 + is formed by the loss of two electrons from the 4 s orbital of the cobalt atom. It has now a total of 25 electrons. Therefore, the electronic configuration can be given as 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 7 or Ar 3 d 7 .

Name the members of the lanthanoid series which exhibit + 4 oxidation state and those which exhibit + 2 oxidation states. Try to correlate this type of behaviour with the electronic configuration of these elements.

The lanthanoids that exhibit + 4 oxidation state are cerium, terbium, promethium and neodymium. Cerium and terbium shows + 4 oxidation. This can be explained in the terms of extra stability of half filled and completely filled 4 f sub-shell respectively in their + 4 oxidation state. Promethium and neodymium shows + 4 oxidation stable because both these tetra positive ions are excess of one or two electrons respectively from the necessary 4 f -sub-shell stable configuration. The lanthanoids that exhibit + 2 oxidation states are europium, ytterbium, samarium and thulium. The + 2 oxidation state of europium and ytterbium can be explained in terms of the extra stability of half filled and completely filled 4 f -sub-shell. Similarly, the + 2 oxidation states of samarium and thulium is because these ions are short of one electron from the necessary half filled and completely filled stable configurations.

E M B I B E

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 20

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12th West Bengal Board

IMPORTANT

Earn 100

Metallic radii of some transition elements are given below Which of these elements will have the highest density?

Element $Fe$ $Co$ $Ni$ $Cu$

Metallic radii/ $pm$ $126$ $125$ $125$ $128$

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Important Questions on d- and f-Block Elements

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12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 21

Generally transition elements form coloured salts due to the presence of unpaired electrons. Which of the following compounds will be coloured in the solid state?

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IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 22

On addition of small amount of

{KMnO}_{4}

to concentrated

H_{2} {SO}_{4}

, a green oily compound is obtained which is highly explosive in nature. Identify the compound from the following.

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12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 23

The magnetic nature of elements depends on the presence of unpaired electrons. Identify the configuration of transition element which shows the highest magnetic moment.

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IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 24

Which of the listed oxidation states is common for all lanthanoids?

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12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 25

Which of the following reactions are disproportionation reactions?

${Cu}^{+} ⟶ {Cu}^{2 +} + Cu$

$3 {MnO}_{4}^{2 -} + 4 H^{+} ⟶ 2 {MnO}_{4}^{-} + {MnO}_{2} + 2 H_{2} O$