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The D-And-f-Block Elements

Question
CBSEENCH12007142
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Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following points:
(i) electronic configuration (ii) oxidation states (iii) ionisation enthalpies and (iv) atomic sizes.

Solution

(i) Electronic configuration:

(ii) Oxidation states:

Sc Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

  

+2 (+2) +3 +3 +4

+2

+3

+4

+5

+2

+3

(+4)

(+5)

+6

+2

(+3)

+4

(+5)

(+6)

+7

(+1)

+2

(+4)

(+5)

(+6)

(+1)

+2

(+3)

(+4)

+ 1

+2

(+3)

(+4)

+ 1

+2

(+3)

(+1)

+2

  

(iii) Ionization enthalpies

In each of the three transition series, the first ionisation enthalpy increases from left to right. However, there are some exceptions. The first ionisation enthalpies of the third transition series are higher than those of the first and second transition series. This occurs due to the poor shielding effect of 4felectrons in the third transition series.

Certain elements in the second transition series have higher first ionisation enthalpies than elements corresponding to the same vertical column in the first transition series. There are also elements in the 2ndtransition series whose first ionisation enthalpies are lower than those of the elements corresponding to the same vertical column in the 1sttransition series.

 

Element

Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

IE, (kJ mol–1)

631

656

650

652

717

762

758

736

745

906


(iv) Atomic Sizes

Atomic size generally decreases from left to right across a period. Now, among the three transition series, atomic sizes of the elements in the second transition series are greater than those of the elements corresponding to the same vertical column in the first transition series. However, the atomic sizes of the elements in the third transition series are virtually the same as those of the corresponding members in the second transition series. This is due to lanthanoid contraction.

Element

Sc

Tc

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

Atomic sizes (pm)

144

132

122

117

117

117

116

115

117

125

 

Some More Questions From The d-And-f-Block Elements Chapter

The E° (M2+/M) value for copper is positive (+ 0.34 V). What is possibility the reason for this? 

How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements?

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Which is a stronger reducing agent Cr2+ or Fe2+ and why?

Explain why Cu+ ion is not stable in aqueous solutions?

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not?

The outer electronic configuration of copper is 3d10 4s1, yet it is considered transition element. Why?

Why the melting points of transition elements are high?

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