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प्रश्न
Reactivity of transition elements decreases almost regularly from Sc to Cu. Explain.
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उत्तर
Reactivity of an element is dependent on the value of ionization enthalpy. In moving from Sc, the first element to Cu, the ionization enthalpy increases regularly. Therefore, the reactivity decreases as we move from Sc to Cu.
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संबंधित प्रश्न
Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?
Why are Mn2+ compounds more stable than Fe2+ towards oxidation to their +3 state?
How is the variability in oxidation states of transition metals different from that of the non-transition metals? Illustrate with examples.
Calculate the number of unpaired electrons in the following gaseous ions:
Mn3+, Cr3+, V3+ and Ti3+. Which one of these is the most stable in an aqueous solution?
What are alloys?
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
How would you account for the following?
Zr (Z = 40) and Hf (Z = 72) have almost identical radii.
Account for the following :
Ti4+ is colourless whereas V4+ is coloured in an aqueous solutions.
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.
Which of the following will not act as oxidising agents?
(i) \[\ce{CrO3}\]
(ii) \[\ce{MoO3}\]
(iii) \[\ce{WO3}\]
(iv) \[\ce{CrO^{2-}4}\]
Match the solutions given in Column I and the colours given in Column II.
| Column I (Aqueous solution of salt) |
Column II (Colour) |
| (i) \[\ce{FeSO2.7H2O}\] | (a) Green |
| (ii) \[\ce{NiCl2.4H2O}\] | (b) Light pink |
| (iii) \[\ce{MnCl2.4H2O}\] | (c) Blue |
| (iv) \[\ce{CoC12,6H2O}\] | (d) Pale green |
| (v) \[\ce{Cu2 Cl2}\] | (e) Pink |
| (f) Colourless |
Match the properties given in Column I with the metals given in Column II.
| Column I (Property) | Column II (Metal) | |
| (i) | Element with highest second ionisation enthalpy |
(a) \[\ce{Co}\] |
| (ii) | Element with highest third ionisation enthalpy |
(b) \[\ce{Cr}\] |
| (iii) | \[\ce{M}\] in \[\ce{M(CO)6}\] is | (c) \[\ce{Cu}\] |
| (iv) | Element with highest heat of atomisation |
(d) \[\ce{Zn}\] |
| (e) \[\ce{Ni}\] |
Catalytic hydrogenation of benzene gives
Why is the `"E"_(("V"^(3+)//"V"^(2+)))^"o"` value for vanadium comparatively low?
Why Zn, Cd and Hg are not called transition metals?
The given graph shows the trends in melting points of transition metals:
Explain the reason why Cr has the highest melting point and manganese (Mn) has a lower melting point.
Write the ionic equation for reaction of KI with acidified KMnO4.
Explain the magnetic properties of d-block (or transition) elements.
Explain the use of different transition metals as catalysts.
