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 27

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IMPORTANT

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There are $14$ elements in actinoid series. Which of the following elements does not belong to this series?

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Important Questions on d- and f-Block Elements

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IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 28

{KMnO}_{4}

acts as an oxidising agent in acidic medium. The number of moles of

{KMnO}_{4}

that will be needed to react with one mole of sulphide ion in acidic solution is

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NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 29

Which of the following are amphoteric oxides:

${Mn}_{2} O_{7}, {CrO}_{3}, {Cr}_{2} O_{3}, CrO, V_{2} O_{5}, V_{2} O_{4}$

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IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 30

Gadolinium belongs to

4 f

series. Its atomic number is

64

. Which of the following is the correct electronic configuration of gadolinium?

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NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 31

Interstitial compounds are formed when small atoms are trapped inside the crystal lattice of metals. Which of the following is not the characteristic property of interstitial compounds?

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NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 32

The magnetic moment is associated with its spin angular momentum and orbital angular momentum. Spin only magnetic moment value of