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प्रश्न
Compare the stability of +2 oxidation state for the elements of the first transition series.
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उत्तर १
| Sc | +3 | ||||||
| Ti | +1 | +2 | +3 | +4 | |||
| V | +1 | +2 | +3 | +4 | +5 | ||
| Cr | +1 | +2 | +3 | +4 | +5 | +6 | |
| Mn | +1 | +2 | +3 | +4 | +5 | +6 | +7 |
| Fe | +1 | +2 | +3 | +4 | +5 | +6 | |
| Co | +1 | +2 | +3 | +4 | +5 | ||
| Ni | +1 | +2 | +3 | +4 | |||
| Cu | +1 | +2 | +3 | ||||
| Zn | +2 |
From the table above, it is evident that Mn exhibits oxidation states ranging from +2 to +7. The number of oxidation states increases as one moves from Sc to Mn. On moving from Mn to Zn, the number of oxidation states decreases due to a decrease in the number of available unpaired electrons. The relative stability of the +2 oxidation state increases as one moves from top to bottom. This is because, on moving from top to bottom, it becomes more and more difficult to remove the third electron from the d-orbital.
उत्तर २
Firstly, in the first half of the transition series, the sum of the first- and second-ionisation enthalpies increases with atomic number. Hence, the standard reducing potential (E°) is low and negative. Hence, the tendency to form M2+ ions decreases. Hence, the +2 oxidation state is more stable in the first half. The greater stability of the +2 oxidation state is due to half-filled d-subshells (d5) in Mn2+, fully filled d-subshells (d10) in Zn2+, and high negative hydration enthalpy in nickel.
संबंधित प्रश्न
The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co
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Give reasons:
Transition metals show variable oxidation states.
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(Atomic nos. : Mn = 25, Cr = 24)
Why are Mn2+ compounds more stable than Fe2+ towards oxidation to their +3 state?
What is meant by ‘disproportionation’?
Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements.
Account for the following :
Ti4+ is colourless whereas V4+ is coloured in an aqueous solutions.
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\[\ce{KMnO4}\] acts as an oxidising agent in acidic medium. The number of moles of \[\ce{KMnO4}\] that will be needed to react with one mole of sulphide ions in acidic solution is ______.
Out of \[\ce{Cu2Cl2}\] and \[\ce{CuCl2}\], which is more stable and why?
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Reason (R): Because it has positive electrode potential.
Catalytic hydrogenation of benzene gives
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[Ti(H2O)]3+ is coloured while [Sc(H2O)6]3+ is colourless.
Account for the following:
Ce4+ is a strong oxidising agent.
Give a reason for the following:
Transition metals possess a great tendency to form complex compounds.
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Based on this information, answer the following question:
- Deduce the structural formula of the complex compound.
- Write the IUPAC name of the complex compound.
- Draw the geometrical isomers of the complex compound.
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Oxidation states
