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प्रश्न
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:
Oxidation states
उत्तर १
Elements in the same horizontal group generally show the same number of oxidation states. The number of oxidation states shown by elements in the middle of each series is maximum, while those at the end are minimum.
उत्तर २
Elements have varying oxidation states in both series. The highest oxidation state corresponds to the total amount of electrons in ‘s’ and ‘d’ orbitals. The 5d transition series shows fewer oxidation states than the 4d series. In 3d series, +2 and +3 oxidation states are common, resulting in stable complexes. In other series, OsO4 and PtF6 are stable at higher oxidation states.
संबंधित प्रश्न
Why +2 oxidation state of manganese is more stable?
Account for the following:
Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows oxidation state of +4.
How would you account for the following?
Zr (Z = 40) and Hf (Z = 72) have almost identical radii.
Dissociation of H2S is suppressed in acidic medium.
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.
Electronic configuration of a transition element X in +3 oxidation state is [Ar]3d5. What is its atomic number?
Explain why does colour of \[\ce{KMNO4}\] disappear when oxalic acid is added to its solution in acidic medium.
Catalytic hydrogenation of benzene gives
Consider the following standard electrode potential values:
\[\ce{Fe^{3+}_{ (aq)} + e^- -> Fe^{2+}_{ (aq)}}\], E0 = +0.77 V
\[\ce{MnO^{-4}_{ (aq)} + 8H^+ + 5e^- -> Mn^{2+}_{ (aq)} + 4H2O_{(l)}}\], E0 = +1.51 V
What is the cell potential for the redox reaction?
A pair of coloured ions is ______.
