Chemistry Class 12 NCERT Solutions: Chapter 8 The d and f Block Elements Part 1

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d and f block elements

D and F Block Elements

d and f block elements

Q: 1. Write down the electronic configuration of:

(i)

(ii)

(iii)

(iv)

(v)

(vi)

(vii)

(viii)

Answer:

(i)

Or,

(ii)

Or,

(iii)

Or,

(iv)

Or,

(v)

Or,

(vi)

Or,

(vii)

Or, [Ar]18 3d5

(viii)

Or,

Q: 2. Why are compounds more stable than towards oxidation to their state?

Answer:

Electronic configuration of

Electronic configuration of

It is known that half-filled and fully7filled orbitals are more stable. Therefore, state has a stable configuration. This is the reason shows resistance to oxidation to configuration and by losing one electron, its configuration changes to a more stable configuration. Therefore, easily gets oxidized to oxidation state.

Q: 3. Explain briefly how state becomes more and more stable in the first half of the first row transition elements with increasing atomic number?

Answer:

The oxidation states displayed by the first half of the first row of transition metals are given in the table below.

Q_3_Oxidation Sate
Q_3_Oxidation Sate

Sc

Ti

V

Cr

Mn

+2

+2

+2

+2

+3

+3

+3

+3

+3

Oxidation state

+4

+4

+4

+4

+5

+5

+6

+6

+7

It can be easily observed that except , all others metals display oxidation state. Also, on moving from to , the atomic number increases from . This means the number of electrons in the also increases from .

oxidation state is attained by the loss of the two electrons by these metals. Since the number of electrons in state also increases from to , the stability of state increases (as orbital is becoming more and more half-filled). electrons (that is half7filled shell, which is highly stable).

Q: 4. 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 examples.

Answer:

The elements in the first half of the transition series exhibit many oxidation states with exhibiting maximum number of oxidation states . The stability of oxidation state increases with the increase in atomic number. This happens as more electrons are getting filled in the orbital. However, does not show oxidation state. Its electronic configuration is . It loses all the three electrons to form oxidation state of is very stable as by losing all three electrons, it attains stable noble gas configuration, are very stable for the same reason. For oxidation state is very stable as after losing two electrons, its is exactly half7filled, .

Q: 5. What may be the stable oxidation state of the transition element with the following electron configurations in the ground state of their atoms and ?

Answer:

Q_5_The Stable Oxidation State of the Transition Element
Q_5_The Stable Oxidation State of the Transition Element

Electronic configuration in ground state

Stable Oxidation states

(i)

(Vanadium)

+2, +3, +4 and +5

(ii)

(Chromium)

+3, +4, +6

(iii)

(Manganese)

+2, +4, +6, +7

(iv)

(Cobalt)

(v)

There is no configuration in ground state