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प्रश्न
Why do transition elements show variable oxidation states ? In 3d series (Sc to Zn), which elements shows the maximum number of oxidation state and why ?
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उत्तर
Transition elements have an incomplete set of d-orbitals in their penultimate shell. They have their valence electrons in (n−1)d- and ns-orbitals. Since there is very little energy difference between these orbitals, electrons from both the energy levels can be used for bond formation. As a result, transition elements exhibit variable oxidation states.
Valence shell electronic configuration for Mn (Z = 25): 3d5 4s2
In the 3d series, Mn has the maximum number of unpaired electrons present in the d-subshell (5 electrons). Hence, Mn exhibits the maximum number of oxidation states, ranging from +2 to +7.
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संबंधित प्रश्न
In 3d series (Sc to Zn), which element has the lowest enthalpy of atomisation and why?
Out of Mn3+ and Cr3+, which is more paramagnetic and why ?
(Atomic nos. : Mn = 25, Cr = 24)
Calculate the ‘spin only’ magnetic moment of \[\ce{M^{2+}_{( aq)}}\] ion (Z = 27).
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: Transition metals form protective oxide films.
Reason: Oxides of transition metals are always stoichiometric.
Electronic configuration of a transition element X in +3 oxidation state is [Ar]3d5. What is its atomic number?
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.
Photographic film and plates have - au essential ingredient of
Why is the `"E"_(("V"^(3+)//"V"^(2+)))^"o"` value for vanadium comparatively low?
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.
Decide which of the following atomic numbers are the atomic numbers of the inner transition elements:
29, 59, 74, 95, 102, 104
