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प्रश्न
Compare the stability of +2 oxidation state for the elements of the first transition series.
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 above table, it is evident that the maximum number of oxidation states is shown by Mn, varying from +2 to +7. The number of oxidation states increases on moving 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 on moving 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 ionization enthalpies increases with increasing atomic number. Hence, the standard reducing potential (EΘ) 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.
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संबंधित प्रश्न
The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co
Answer the following: Which element shows only +3 oxidation state?
Why do the transition elements have higher enthalpies of atomisation?
What are the transition elements? Write two characteristics of the transition elements.
Which of the 3d series of the transition metals exhibits the largest number of oxidation states and why?
What are the characteristics of the transition elements and why are they called transition elements?
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 point:
Electronic configurations
Write the factors which are related to the colour of transition metal ions.
How would you account for the following?
Zr (Z = 40) and Hf (Z = 72) have almost identical radii.
Give reasons: Sc3+ is colourless in aqueous solution whereas Ti3+ is coloured.
Read the passage given below and answer the following question:
The transition metals when exposed to oxygen at low and intermediate temperatures form thin, protective oxide films of up to some thousands of Angstroms in thickness. Transition metal oxides lie between the extremes of ionic and covalent binary compounds formed by elements from the left or right side of the periodic table. They range from metallic to semiconducting and deviate by both large and small degrees from stoichiometry. Since electron bonding levels are involved, the cations exist in various valence states and hence give rise to a large number of oxides. The crystal structures are often classified by considering a cubic or hexagonal close-packed lattice of one set of ions with the other set of ions filling the octahedral or tetrahedral interstices. The actual oxide structures, however, generally show departures from such regular arrays due in part to distortions caused by packing of ions of different size and to ligand field effects. These distortions depend not only on the number of d-electrons but also on the valence and the position of the transition metal in a period or group.
In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.
Assertion: Cations of transition elements occur in various valence states.
Reason: Large number of oxides of transition elements are possible.
Electronic configuration of a transition element X in +3 oxidation state is [Ar]3d5. What is its atomic number?
Transition elements show magnetic moment due to spin and orbital motion of electrons. Which of the following metallic ions have almost same spin only magnetic moment?
(i) \[\ce{Co^{2+}}\]
(ii) \[\ce{Cr^{2+}}\]
(iii) \[\ce{Mn^{2+}}\]
(iv) \[\ce{Cr^{3+}}\]
Assertion: Separation of \[\ce{Zr}\] and \[\ce{Hf}\] is difficult.
Reason: Because \[\ce{Zr}\] and \[\ce{Hf}\] lie in the same group of the periodic table.
Identify the metal and justify your answer.
Carbonyl \[\ce{M(CO)5}\]
Why are fluorides of transition metals more stable in their higher oxidation state as compared to the lower oxidation state?
On strong heating AgNO3, the gases evolved are:-
The number of terminal oxygen atoms present in the product B obtained from the following reactions is:
\[\ce{FeCr2O4 + Na2CO3 + O2 -> A + Fe2O3 + CO2}\]
\[\ce{A + H^+ -> B + H2O + Na^+}\]
A pair of coloured ions is ______.
The compounds of \[\ce{Ti^4+}\] ions are colourless due to ______.
