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प्रश्न
Give reasons for the following:
The transition metals generally form coloured compounds.
Explain giving reasons:
The transition metals generally form coloured compounds.
Compounds of transition metals are generally coloured. Give reason.
Why the transition metals generally form coloured compounds?
Explain giving reasons:
Transition elements usually form coloured ions.
Why are most of the transition metals and their compounds coloured? Explain.
Explain why transition elements usually form coloured ions.
Why are the compounds of transition elements coloured?
Examine the following observation:
Transition elements generally form coloured compounds.
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उत्तर
Most transition metal ions are coloured in solution and solid states. This is due to the partial absorption of visible light. The absorbed light excites the electron from one orbital to another orbital of the same d-subshell. Since the electronic transitions occur in the d-orbitals of metal ions, they are called d-d transitions. These appear coloured due to the d-d transitions that occur in transition metal ions by absorbing visible light.
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संबंधित प्रश्न
In 3d series (Sc to Zn), which element has the lowest enthalpy of atomisation and why?
Explain why Cu+ ion is not stable in aqueous solutions?
What are inner transition elements?
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
The transition metals show _________ character because of the presence of unpaired· electrons and Cu+ is ____________ because of its electronic configuration is [Ar]3d10
The paramagnetic character in the 3d-transition series elements increases up to Mn and then decreases.
Explain why transition elements form alloys.
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: Cations of transition elements occur in various valence states.
Reason: Large number of oxides of transition elements are possible.
Electronic configuration of a transition element X in +3 oxidation state is [Ar]3d5. What is its atomic number?
Transition elements form binary compounds with halogens. Which of the following elements will form \[\ce{MF3}\] type compounds?
(i) \[\ce{Cr}\]
(ii) \[\ce{Co}\]
(iii) \[\ce{Cu}\]
(iv) \[\ce{Ni}\]
Transition elements show high melting points. Why?
When a brown compound of manganese (A) is treated with \[\ce{HCl}\] it gives a gas (B). The gas taken in excess, reacts with \[\ce{NH3}\] to give an explosive compound (C). Identify compounds A, B and C.
Ionisation enthalpies of Ce, Pr and Nd are higher than Th, Pa and U. Why?
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) \[\ce{Ni}\] |
Mention any three processes where transition metals act as catalysts.
On the basis of the figure given below, answer the following questions:
- Why Manganese has lower melting point than Chromium?
- Why do transition metals of 3d series have lower melting points as compared to 4d series?
- In the third transition series, identify and name the metal with the highest melting point.
Photographic film and plates have - au essential ingredient of
Why Zn, Cd and Hg are not called transition metals?
Account for the following:
Sc3+ is colourless whereas Ti3+ is coloured in an aqueous solution.
Why are interstitial compounds well known for transition metals?
