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Questions
Transition elements show high melting points. Why?
Explain giving reasons:
Transition elements have higher melting and boiling points.
Why do transition elements have much higher melting points?
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Solution 1
The high melting points of transition metals are attributed to the involvement of greater number of electrons in the interatomic metallic bonding from (n – 1) d-orbitals in addition to ns electrons.
Solution 2
- Transition elements have higher melting and boiling points because their atoms are held together by strong metallic bonds.
- These metallic bonds have significant covalent character due to the presence of unpaired d-electrons that overlap between atoms.
- More unpaired d-electrons mean more covalent bonding and stronger metallic bonds, which require more energy to break.
- The close-packed structures of transition metals also contribute to the strong bonding and thus high melting and boiling points.
- Melting and boiling points generally increase up to the middle of the series because the number of unpaired d-electrons also increases up to that point.
RELATED QUESTIONS
Account for the following:
Cr2+ is a strong reducing agent.
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`MnO_4^(-) + H_2O + I^(-) ->`
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Reason (R): Because it has positive electrode potential.
Sodium this sulphate is used in photography because of its:-
The number of terminal oxygen atoms present in the product B obtained from the following reactions is:
\[\ce{FeCr2O4 + Na2CO3 + O2 -> A + Fe2O3 + CO2}\]
\[\ce{A + H^+ -> B + H2O + Na^+}\]
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Reason (R): The ability of oxygen to form multiple bonds to metals.
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\[\ce{Fe^{3+}_{ (aq)} + e^- -> Fe^{2+}_{ (aq)}}\], E0 = +0.77 V
\[\ce{MnO^{-4}_{ (aq)} + 8H^+ + 5e^- -> Mn^{2+}_{ (aq)} + 4H2O_{(l)}}\], E0 = +1.51 V
What is the cell potential for the redox reaction?
Write the number of unpaired electrons in Cr3+.
(Atomic number of Cr = 24)
Write the ionic equation for reaction of KI with acidified KMnO4.
A pair of coloured ions is ______.
Explain the use of different transition metals as catalysts.
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with H2S.
For M2+/M and M3+/M2+systems, the EΘ values for some metals are as follows:
| Cr2+/Cr | −0.9 V |
| Mn2+/Mn | −1.2 V |
| Fe2+/Fe | −0.4 V |
| Cr3/Cr2+ | −0.4 V |
| Mn3+/Mn2+ | +1.5 V |
| Fe3+/Fe2+ | +0.8 V |
Use this data to comment upon:
The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
