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 10

HARD

12th West Bengal Board

IMPORTANT

Earn 100

What is the oxidation state of $Ni$ in $Ni {(CO)}_{4} ?$

Important Questions on d- and f-Block Elements

HARD

12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 11

Give plausible reason for the fact that the first ionization enthalpies of the

5 d

-transition metals are higher than those of the

3 d

and

Ni {(CO)}_{4}

transition metals.

MEDIUM

12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 11

Explain how the colour of a solution of

K_{2} {Cr}_{2} O_{7}

depends on the

pH

of a solution?

EASY

12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 11

Write a balanced equation for the reaction of

K_{2} {Cr}_{2} O_{7}

with ferrous sulphate in the presence of dil.

H_{2} {SO}_{4}

.

EASY

12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 12

Explain why transition metals form:

alloys with other transition metals easily.

EASY

12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 12

Explain why transition metals form:

compounds in different oxidation states.

MEDIUM

12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 12

What are interstitial compounds? Explain them with reference to transition metals and mention their two important properties.

HARD

12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 13

Represent by ionic equation, the oxidising action of ${MnO}_{4}^{-}$ both in acidic and alkaline media. Write the balanced chemical equation of ${SO}_{2}$ and ${MnO}_{4}^{-}$ in acidic medium.

HARD

12th West Bengal Board

IMPORTANT

NEW SYSTEMATIC MODERN CHEMISTRY>Chapter 8 - d- and f-Block Elements>REVIEW EXERCISES>Q 13

Decide giving reasons which one of the following exhibits the property indicated:

(i) ${Sc}^{3 +}$ and ${Cr}^{3 +}$ Exhibits paramagnetism.

(ii) $V or Mn$ Exhibit number of oxidation states (at. no. $Sc = 21, V = 23, Cr = 24, Mn = 25$ )