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प्रश्न
How would you account for the irregular variation of ionization enthalpies (first and second) in the first series of the transition elements?
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उत्तर
- Ionization enthalpies are found to increase in the given series due to a continuous filling of the inner d-orbitals. The irregular variations of ionization enthalpies can be attributed to the extra stability of configurations such as d0, d5 and d10. Since these states are exceptionally stable, their ionization enthalpies are very high.
- In terms of first ionization energy, Cr has a low ionization energy. This is because after losing one electron, it attains the stable configuration (3d5). On the other hand, Zn has exceptionally high first ionization energy, as an electron has to be removed from stable and fully-filled orbitals (3d10 4s2).
- The second ionization energies are higher than the first since it becomes difficult to remove an electron when an electron has already been removed. Also, elements like Cr and Cu have exceptionally high second ionization energies, as after losing the first electron, they have attained the stable configuration (Cr+: 3d5 and Cu+: 3d10). Hence, removing one more electron from this stable configuration will require a lot of energy.
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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: Write the element which shows maximum number of oxidation states. Give reason.
In 3d series (Sc to Zn), which element has the lowest enthalpy of atomisation and why?
Account for the following:
Zn is not considered as a transition element.
Out of Mn3+ and Cr3+, which is more paramagnetic and why ?
(Atomic nos. : Mn = 25, Cr = 24)
What are the characteristics of the transition elements and why are they called transition elements?
Account for the following :
Ti4+ is colourless whereas V4+ is coloured in an aqueous solutions.
Explain why Mn2+ is more stable than Fe2+ towards oxidation to +3 state. (At. no. of Mn = 25, Fe = 26)
Maximum oxidation state is shown by ____________.
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: Crystal structure of oxides of transition metals often show defects.
Reason: Ligand field effect cause distortions in crystal structures.
Why does copper not replace hydrogen from acids?
Explain why does colour of KMnO4 disappear when oxalic acid is added to its solution in acidic medium.
The halides of transition elements become more covalent with increasing oxidation state of the metal. Why?
Assertion (A): Cu cannot liberate hydrogen from acids.
Reason (R): Because it has positive electrode potential.
Account for the following:
In case of transition elements, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number.
Catalytic hydrogenation of benzene gives
Sodium this sulphate is used in photography because of its:-
Which of the following maxm magnetic moment?
Account for the following:
Transition metals form alloys.
A pair of coloured ions is ______.
The E° value for the Mn2+/Mn2+ couple is more positive than that of Cr3+/Cr2+ or Fe3+/Fe2+ due to the change of:
