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प्रश्न
Why Zn, Cd and Hg are not called transition metals?
Account for the following:
Zn, Cd and Hg are not called transition elements.
Explain giving reason:
Zn, Cd and Hg are not regarded as transition elements.
Why are Zn, Cd and Hg not regarded as transition elements?
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उत्तर १
The orbitals of elements such as Zn, Cd and Hg are totally occupied when they are in their ground state as well as their general oxidation state. As a result, these elements are not considered transition elements.
उत्तर २
- Zn, Cd, and Hg have completely filled d-orbitals in their atoms and common ions (Zn2+, Cd2+, Hg2+).
- Their electronic configurations show no partly filled d-orbitals.
- Transition elements are defined as d-block elements having partly filled d-orbitals in their atoms or common ions.
- Since Zn, Cd, and Hg lack partly filled d-orbitals, they do not meet the definition of transition elements.
- Hence, Zn, Cd, and Hg are not regarded as transition elements.
Notes
Students can refer to the provided solutions based on their preferred marks.
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संबंधित प्रश्न
Why do interstitial compounds have higher melting points than corresponding pure metals?
Which of the following cations are coloured in aqueous solutions and why ?
Sc3+, V3+, Ti4+, Mn2+ (At. Nos. Sc = 21, V = 23, Ti = 22, Mn = 25)
For M2+/M and M3+/M2+ systems, the E° 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:
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- the ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
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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.
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.
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\[\ce{FeCr2O4 + Na2CO3 + O2 -> A + Fe2O3 + CO2}\]
\[\ce{A + H^+ -> B + H2O + Na^+}\]
