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The d-And-f-Block Elements

Short Answer Type

121.

What is the effect of increasing pH in K₂Cr₂O₇, solution?

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122.

Within a periodic group of transition elements the possibility of exhibiting maximum oxidation state increases with atomic number. Why?

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123. Write down the electronic configuration of:
(i) Cr³⁺ (ii) Cu⁺ (iii) Co²⁺(iv) Mn²⁺ (v) Pm³⁺(vi) Ce⁴⁺ (vii) Lu²⁺ (viii) Th⁴⁺

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124. Why are Mn²⁺ compounds more stable than Fe²⁺ towards oxidation to their +3 state?

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Long Answer Type

125. Explain briefly how +2 state becomes more and more stable in the first half of the first row transition elements with increasing atomic number?

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126. To what extent do the electronic configurations decide the stability of oxidation states in the first series of the transition elements? Illustrate your answer with example.

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Short Answer Type

127. What may be the stable oxidation state of the transition element with the following d electron configurations in the ground state of their atoms: 3d³, 3d⁵, 3d⁸ and 3d⁴?

The stable oxidation state of transition element with the d electron configuration in ground state of atoms are as follows:

S. No. d-electron

configuration

Symbol of element

Stable oxidation states

3d³

3d⁴

3d⁵

3d⁸

Vanadium[V](4s²3d³)

Chromium Cr(4s²3d⁴)

Manganes Mn(4s²3d⁵)

Nickel Ni(4s²3d⁸)

+2, +3, +5

+2, +3, +6

+2,+7

+2,+4

It should be noted that lower stable oxidation state generally leads to ionic bond and higher oxidation state corresponds to covalent bond.

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128. Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.

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Long Answer Type

129. What is lanthanoid contraction? What are the consequences of lanthanoid contraction?

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130. What are the characteristics of the transition elements and why are they called transition elements? Which of the d-block elements may not be regarded as the transition elements?

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