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प्रश्न
How would you account for the following?
Zr (Z = 40) and Hf (Z = 72) have almost identical radii.
उत्तर
This is because the atomic radii of 4d and 5d transition elements are nearly same. This similarity in size is consequence of lanthanide contraction. Because of this lanthanide contraction the radii of Hf becomes nearly equal to that of Zr.
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संबंधित प्रश्न
Why +2 oxidation state of manganese is more stable?
Account for the following:
Cu+ ion is unstable in aqueous solution.
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
Give reasons for the following:
The transition metals generally form coloured compounds.
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?
Assertion: \[\ce{Cu}\] cannot liberate hydrogen from acids.
Reason: Because it has positive electrode potential.
Identify the metal and justify your answer.
Carbonyl \[\ce{M(CO)5}\]
Account for the following:
Sc3+ is colourless whereas Ti3+ is coloured in an aqueous solution.
In order to protect iron from corrosion, which one will you prefer as a sacrificial electrode, Ni or Zn? Why? (Given standard electrode potentials of Ni, Fe and Zn are -0.25 V, -0.44 V and -0.76 V respectively.)
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.
