Advertisements
Advertisements
प्रश्न
Which of the d-block elements may not be regarded as the transition elements?
Advertisements
उत्तर
The electronic configuration of Zn, Cd and Hg is represented by the general formula (n – 1)d10ns2. In these elements, the orbitals are completely filled in the ground (normal) state as well as in ordinary oxidation states, i.e., the subshells are not incomplete in their atomic state or any one of the ionic states. Therefore, they cannot be called transition elements.
संबंधित प्रश्न
Account for the following:
Zn is not considered as a transition element.
In the series Sc (Z = 21) to Zn (Z = 30), the enthalpy of atomization of zinc is the lowest, i.e., 126 kJ mol−1. Why?
What is meant by ‘disproportionation’?
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?
Use Hund’s rule to derive the electronic configuration of Ce3+ ion and calculate its magnetic moment on the basis of ‘spin-only’ formula.
An analysis shows that FeO has a non-stoichiometric composition with formula Fe0.95O. Give reason.
Dissociation of H2S is suppressed in acidic medium.
Which among the following transition metal has the lowest melting point?
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.
Interstitial compounds are formed when small atoms are trapped inside the crystal lattice of metals. Which of the following is not the characteristic property of interstitial compounds?
Transition elements show high melting points. Why?
The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why?
Which of the following is non-metallic?
The orientation of an atomic orbital is governed by
Which one of the following characters tie of the transition metal is associated with higher catalytic activity?
Match List - I with List - II.
| List - I | List - II | ||
| (A) | [Fe(CN)6]3− | (i) | 5.92 BM |
| (B) | [Fe(H2O)6]3+ | (ii) | 0 BM |
| (C) | [Fe(CN)6]4− | (iii) | 4.90 BM |
| (D) | [Fe(H2O)6]2+ | (iv) | 1.73 BM |
Choose the correct answer from the options given below.
Give reasons for the following statement:
Transition metals and most of their compounds show paramagnetic behaviour.
Assertion (A): Transition metals have high enthalpy of atomisation.
Reason (R): Greater number of unpaired electrons in transition metals results in weak metallic bonding.
Account for the following:
Copper has an exceptionally positive `"E"_("M"^(2+)//"M")^0` value.
Explain the magnetic properties of d-block (or transition) elements.
