Chapter-8 The d-and f-Block Elements

A violet compound of manganese (A) decomposes on heating to liberate oxygen
and compounds (B) and (C) of manganese are formed. Compound (C) reacts
with KOH in the presence of potassium nitrate to give compound (B). On
heating compound (C) with conc. H2SO4 and NaCl, chlorine gas is liberated
and a compound (D) of manganese along with other products is formed.
Identify compounds A to D and also explain the reactions involved.

A violet compound of manganese (A) decomposes on heating to liberate oxygen
and compounds (B) and (C) of manganese are formed. Compound (C) reacts
with KOH in the presence of potassium nitrate to give compound (B). On
heating compound (C) with conc. H2SO4 and NaCl, chlorine gas is liberated
and a compound (D) of manganese along with other products is formed.
Identify compounds A to D and also explain the reactions involved.

(a) Transition metals can act as catalysts because these can change their
oxidation state. How does Fe(III) catalyse the reaction between iodide
and persulphate ions?
(b) Mention any three processes where transition metals act as catalysts.

Mention the type of compounds formed when small atoms like H, C and N get
trapped inside the crystal lattice of transition metals. Also give physical and
chemical characteristics of these compounds.

When an oxide of manganese (A) is fused with KOH in the presence of an
oxidising agent and dissolved in water, it gives a dark green solution of
compound (B). Compound (B) disproportionates in neutral or acidic solution
to give purple compound (C). An alkaline solution of compound (C) oxidises
potassium iodide solution to a compound (D) and compound (A) is also formed.
Identify compounds A to D and also explain the reactions involved.

When a chromite ore (A) is fused with sodium carbonate in free excess of air
and the product is dissolved in water, a yellow solution of compound (B) is
obtained. After treatment of this yellow solution with sulphuric acid,
compound (C) can be crystallised from the solution. When compound (C) is
treated with KCl, orange crystals of compound (D) crystallise out. Identify A
to D and also explain the reactions.

When a chromite ore (A) is fused with sodium carbonate in free excess of air
and the product is dissolved in water, a yellow solution of compound (B) is
obtained. After treatment of this yellow solution with sulphuric acid,

Match the statements given in Column I with the oxidation states given in
Column II.
Column I                                                                    Column II
(i) Oxidation state of Mn in MnO2 is                                (a) + 2
(ii) Most stable oxidation state of Mn is                            (b) + 3
(iii) Most stable oxidation state of                                   (c) + 4
Mn in oxides is                                                            (d) + 5
(iv) Characteristic oxidation                                            (e) + 7
state of lanthanoids is

Match the properties given in Column I with the metals given in Column II.
Column I (Property)                                              Column II (Metal)
(i) An element which can show                                (a) Mn
+8 oxidation state
(ii) 3d block element that can show                          (b) Cr
upto +7 oxidation state                                          (c) Os
(iii) 3d block element with highest                            (d) Fe
melting point

Match the compounds/elements given in Column I with uses given in Column II.
Column I (Compound/element)                                              Column II (Use)
(i) Lanthanoid oxide                                                   (a) Production of iron alloy
(ii) Lanthanoid                                                           (b) Television screen
(iii) Misch metal                                                         (c) Petroleum cracking
(iv) Magnesium based alloy is constituent of                     (d) Lanthanoid metal + iron

(v) Mixed oxides of   lanthanoids are employed                 (e) Bullets
                                                                               (f) In X-ray screen

Reactivity of transition elements decreases almost regularly from Sc to Cu.
Explain.

While filling up of electrons in the atomic orbitals, the 4s orbital is filled
before the 3d orbital but reverse happens during the ionisation of the atom.
Explain why?

The halides of transition elements become more covalent with increasing
oxidation state of the metal. Why?

EV of Cu is + 0.34V while that of Zn is – 0.76V. Explain.

The second and third rows of transition elements resemble each other much
more than they resemble the first row. Explain why?

Although +3 oxidation states is the characteristic oxidation state of lanthanoids
but cerium shows +4 oxidation state also. Why?

Although Zr belongs to 4d and Hf belongs to 5d transition series but it is
quite difficult to separate them. Why?

Ionisation enthalpies of Ce, Pr and Nd are higher than Th, Pa and U. Why?

Although fluorine is more electronegative than oxygen, but the ability of oxygen
to stabilise higher oxidation states exceeds that of fluorine. Why?

When a brown compound of manganese (A) is treated with HCl it gives a gas
(B). The gas taken in excess, reacts with NH3 to give an explosive compound
(C). Identify compounds A, B and C.

When a brown compound of manganese (A) is treated with HCl it gives a gas
(B). The gas taken in excess, reacts with NH3 to give an explosive compound
(C). Identify compounds A, B and C.

When Cu2+ ion is treated with KI, a white precipitate is formed. Explain the
reaction with the help of chemical equation.

Transition elements show high melting points. Why?

Why first ionisation enthalpy of Cr is lower than that of Zn ?

Why EV values for Mn, Ni and Zn are more negative than expected?

Why does copper not replace hydrogen from acids?

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

Explain why transition elements have many irregularities in their electronic configurations? 

What are different oxidation states exhibited by Lanthanides?

How is the variability in oxidation states of transition metals different from that of the non‐

transition metals? Illustrate with examples

Why do transition elements show variable oxidation states?

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

To what extend do the electronic configuration decide the stability of oxidation state in the first series of the transition elements? Illustrate your answer with an example.

What is meant by disproportionation Give two examples.? 

Which metal in the first series of transition metals exhibits +1 oxidation state most frequently and why?

What are inner transition elements?

The paramagnetic character in 3d‐transition series elements increases upto Mn and then

decreases. Explain why?

Comment  on  the  statement  that  elements  of  the  first  transition  series  possess  many properties different from those of heavier transition metal

What  are  interstitial  compounds?  Why  are  such    compounds  well  known  for  transition metal?

a) Describe the general trends in the following properties of the first series of the transition elements:‐

(i) Stability of +2‐oxidation state

(ii) Formation of oxometal ions

(b) Write steps involved in the preparation of KMnO4 from K2MnO4

a) Write the steps involve in the preparation of K2Cr2O7 from chromite ore. (b) What is the effect of pH on dichromate ion solution?

(a) What is lanthanide contraction? What effect does it have on the chemistry of the elements, which follow lanthanoids?

(b) The chemistry of actinoid elements is not so much smooth as that of lanthanoids. Justify these statements by giving some examples from the oxidation state of these elements.

Give  examples  and  suggest  reasons  for  the  following  features  of  the  transition  metal chemistry:

(i) The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.

(ii)    A transition metal exhibits highest oxidation state in oxides and fluorides.

(iii)  Of the d4 species, Cr2+ is strongly reducing while manganese(III)is strongly oxidizing.

Fe2+/Fe           ‐0.4V                                           Fe3+/Fe2+                                     +0.8V Use this data to comment upon :‐

(i)the stability of Fe3+ in acid solution as compared to Cr3+ or Mn3+ and

(ii)the ease with which iron can be oxidized as compared to a similar process for either chromium or manganese metal.

Account for the following statements:

(i)Cobalt (II) is stable in aqueous solution but in the presence of strong ligands and air, it can be oxidized to Co (III).

(ii)The d1 configuration is very unstable in ions.

(iii)One among the lanthanides, Ce (III) can be easily oxidized to Ce (IV).

Compare the chemistry of actinides with that of the lanthanoids with special reference to: (i) electronic configuration                                  (iii) oxidation state

(ii) atomic and ionic sizes and                             (iv) chemical reactivity

a)  What  is  actinides  contraction?  What  effect  does  it  have  on  the  chemistry  of  the elements, which follow actinides?

(b) Name an important alloy, which contains some of the lanthanide metals. Mention its uses.

(ii) The enthalpies of atomisation of the transition metals are high. (iii) The transition metals generally form coloured compounds.

(iv) Transition metals and their many compounds act as good catalyst. (v)Transition metals have a strong tendency to form complexes.

Give reasons for the following:‐

(i) Fe has higher melting point than Cu.

(ii) [Ti (H2O)6]3+ is coloured while [Sc(H20)6] is colourless.

(iii)The 4d and 5d series of transition metals have more frequent metal‐metal bonding in

their compound than do the 3d metals.

(iv)Transition metals some time exhibit very low oxidation state such as +1and 0. (v)Hg is not considered a transition metal.

(a) write electronic configuration of element having atomic number 101. (b) Which element show maximum oxidation state in 3d transition series?

(c) What is mischmetal?

(d) Explain why Cu+  ion is not stable in aqueous solution?

(e) Name the transition metal which is well known to exhibit +4 oxidation state? 

Give reasons for the following:‐

(i) Transition metals have high enthalpy of hydration. (ii) Zn, Cd and Hg are not regarded as transition metal.

(iii) d block elements exhibit a large number of oxidation state than f block elements.

(iv)The second and third members in each group of transition element have similar atomic radii.

(v) K2 [PtCl6] is well known compound whereas the corresponding Ni compound is not known.

What can be inferred from the magnetic moment values of the following complex species?

Example Magnetic Moment (BM)

K₄[Mn(CN)₆] 2.2

[Fe(H₂O)₆]²⁺ 5.3

K₂[MnCl₄] 5.9

Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements.

Write down the number of 3d electrons in each of the following ions:

Ti²⁺, V²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Fe³⁺, CO²⁺, Ni²⁺ and Cu²⁺.

Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).

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 configurations,

(ii) oxidation states,

(iii) ionisation enthalpies, and

(iv) atomic sizes.

Write the electronic configurations of the elements with the atomic numbers 61, 91, 101, and 109.

Compare the chemistry of the actinoids with that of lanthanoids with reference to:

(i) electronic configuration

(ii) oxidation states and

(iii) chemical reactivity.

Name the members of the lanthanoid series which exhibit +4 oxidation state and those which exhibit +2 oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.

Use Hund's rule to derive the electronic configuration of Ce³⁺ ion and calculate its magnetic moment on the basis of 'spin-only' formula.

Which is the last element in the series of the actinoids? Write the electronic configuration of this element. Comment on the possible oxidation state of this element.

The chemistry of the actinoid elements is not so smooth as that of the Lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.

What are inner transition elements? Decide which of the following atomic numbers are the atomic numbers of the inner transition elements: 29, 59, 74, 95, 102, 104.

What are alloys? Name an important alloy which contains some of thelanthanoid metals. Mention its uses.

Indicate the steps in the preparation of:

(i) K2Cr2O7 from chromite ore.

(ii) KMnO4 from pyrolusite ore.

Give examples and suggest reasons for the following features of the transition metal chemistry:

(i)The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.

(ii)A transition metal exhibits highest oxidation state in oxides and fluorides.

(iii) The highest oxidation state is exhibited in oxoanions of a metal.

Calculate the number of unpaired electrons in the following gaseous ions: Mn³⁺, Cr³⁺, V³⁺ and Ti³⁺. Which one of these is the most stable in aqueous solution?

Which metal in the first series of transition metals exhibits +1 oxidationstate most frequently and why?

What is meant by 'disproportionation'? Give two examples of disproportionation reaction in aqueous solution.

How would you account for the following:

(i) Of the d⁴species, Cr²⁺is strongly reducing while manganese(III) is strongly oxidising.

(ii) Cobalt(II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidised.

(iii) The d¹configuration is very unstable in ions.

Compare the chemistry of actinoids with that of the lanthanoids with specialreference to:

(i) electronic configuration (iii) oxidation state

(ii) atomic and ionic sizes and (iv) chemical reactivity.

Compare the stability of +2 oxidation state for the elements of the first transition series.

Predict which of the following will be coloured in aqueous solution? Ti³⁺, V³⁺,

Cu⁺, Sc³⁺, Mn²⁺, Fe³⁺ and Co²⁺. Give reasons for each.

For M²⁺/M and M³⁺/M²⁺ systems, the  values for some metals are as follows:

Cr²⁺/Cr -0.9V

Cr³/Cr²⁺ -0.4 V

Mn²⁺/Mn -1.2V

Mn³⁺/Mn²⁺ +1.5 V

Fe²⁺/Fe -0.4V

Fe³⁺/Fe²⁺ +0.8 V

Use this data to comment upon:

(i) The stability of Fe³⁺in acid solution as compared to that of Cr³⁺or Mn³⁺ and

(ii) The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.

Describe the preparation of potassium permanganate. How does the acidifiedpermanganate solution react with (i) iron(II) ions (ii) SO₂and (iii) oxalic acid?

Write the ionic equations for the reactions.

Describe the oxidising action of potassium dichromate and write the ionicequations for its reaction with:

(i) iodide (ii) iron(II) solution and (iii) H₂S

Describe the preparation of potassium dichromate from iron chromite ore.

What is the effect of increasing pH on a solution of potassium dichromate?

How is the variability in oxidation states of transition metals different from

that of the non-transition metals? Illustrate with examples.

What are interstitial compounds? Why are such compounds well known for

transition metals?

Explain giving reasons:

(i) Transition metals and many of their compounds show paramagnetic

behaviour.

(ii) The enthalpies of atomisation of the transition metals are high.

(iii) The transition metals generally form coloured compounds.

(iv) Transition metals and their many compounds act as good catalyst.

What are the different oxidation states exhibited by the lanthanoids?

In what way is the electronic configuration of the transition elements different

from that of the non-transition elements?

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?

What is lanthanoid contraction? What are the consequences of lanthanoid

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.

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, 3d⁸and 3d⁴?

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.

Explain briefly how +2 state becomes more and more stable in the first half

of the first row transition elements with increasing atomic number?

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

Write down the electronic configuration of:

(i) Cr³⁺+ (iii) Cu⁺ (v) Co²+ (vii) Mn²⁺

(ii) Pm³⁺ (iv) Ce⁴⁺ (vi) Lu²⁺ (viii) Th⁴⁺

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

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

Calculate the 'spin only' magnetic moment of M²⁺_(aq) ion (Z = 27).

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

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

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

The E^θ(M²⁺/M) value for copper is positive (+0.34V). What is possibly the reason for this? (Hint: consider its high Δ_aH^θ and low Δ_hydH^θ)

Which of the 3d series of the transition metals exhibits the largest number of oxidation states and why?

Silver atom has completely filled d orbitals (4d¹⁰) in its ground state. How can you say that it is a transition element?