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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:
Electronic configurations
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उत्तर
The electronic configurations of the elements of the same group are generally similar.
The first transition series shows two exceptions:
Cr = 3d5 4s1 and Cu = 3d10 4s1
The second series shows more exceptions:
Mo (42) = 4d5 5s1, Tc (43) = 4d6 5s1, Ru (44) = 4d7 5s1, Rh (45) = 4d8 5s1, Pd (46) = 4d10 5s0, Ag (47) = 4d10 5s1
Similarly, the third series shows exceptions:
W (74) = 5d4 6s1, Pt (78) = 5d9 6s1, and Au (79) = 5d10 6s1
The first transition series gradually fills 3d-orbitals, whereas the second and third transition series gradually fill 4d-orbitals and 5d-orbitals, respectively. Therefore, in many cases in the horizontal series, the electronic configurations of the three series are not the same.
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संबंधित प्रश्न
Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?
Give reasons:
Transition metals show variable oxidation states.
Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?
Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements.
Give reasons Iron has the higher enthalpy of atomization than that of copper.
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.
Out of \[\ce{Cu2Cl2}\] and \[\ce{CuCl2}\], which is more stable and why?
Although fluorine is more electronegative than oxygen, but the ability of oxygen to stabilise higher oxidation states exceeds that of fluorine. Why?
Although \[\ce{Cr^3+}\] and \[\ce{Co^2+}\] ions have same number of unpaired electrons but the magnetic moment of \[\ce{Cr^3+}\] is 3.87 B.M. and that of \[\ce{Co^2+}\] is 4.87 B.M. Why?
The halides of transition elements become more covalent with increasing oxidation state of the metal. Why?
While filling up of electrons in the atomic orbitals, the 4s orbital is filled before the 3d orbital but reverse happens during the ionisation of the atom. Explain why?
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.
On strong heating AgNO3, the gases evolved are:-
Which of the following ions has the maximum magnetic moment?
Account for the following:
Transition metals form alloys.
Which of the following ions has the electronic configuration 3d6?
(Atomic number: Mn = 25, Co = 27, Ni = 28)
Consider the following standard electrode potential values:
\[\ce{Sn^{2+}_{ (aq)} + 2e^- -> Sn_{(s)}}\]; E0 = −0.14 V
\[\ce{Fe^{3+}_{ (aq)} + e^- -> Fe^{2+}_{ (aq)}}\]; E0 = +0.77 V
What is the cell reaction and potential for the spontaneous reaction that occurs?
Explain the use of different transition metals as catalysts.
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:
Atomic sizes
