Advertisements
Advertisements
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:
Atomic sizes
Advertisements
उत्तर
- Generally, ions or atoms of the same charge in a series show a gradual decrease in radius with increasing atomic number, although this decrease is very small.
- But the size of the atoms of the 4d series is larger than the corresponding elements of the 3d series, while the size of the corresponding elements of the 5d series is almost the same. The reason for this is lanthanoid contraction.
APPEARS IN
संबंधित प्रश्न
Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?
ln which pair highest oxidation states of transition metals are found:
Why +2 oxidation state of manganese is more stable?
Why do the transition elements have higher enthalpies of atomisation?
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
Give reasons: Sc3+ is colourless in aqueous solution whereas Ti3+ is coloured.
Account for the following :
Ti4+ is colourless whereas V4+ is coloured in an aqueous solutions.
In lake test for Al3+ ions, there is the formation of coloured ‘floating lake’. It is due to ______.
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.
The magnetic moment is associated with its spin angular momentum and orbital angular momentum. Spin only magnetic moment value of \[\ce{Cr^{3+}}\] ion is ______.
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.
EΘ of Cu is + 0.34V while that of Zn is – 0.76V. Explain.
When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallised from the solution. When compound (C) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.
A violet compound of manganese (A) decomposes on heating to liberate oxygen and compounds (B) and (C) of manganese are formed. Compound (C) reacts with KOH in the presence of potassium nitrate to give compound (B). On heating compound (C) with conc. \[\ce{H2SO4}\] and \[\ce{NaCl}\], chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.
Which of the following ions will exhibit colour in aqueous solution?
Which of the following ions has the maximum magnetic moment?
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.
Which of the following ions has the electronic configuration 3d6?
(Atomic number: Mn = 25, Co = 27, Ni = 28)
Explain the use of different transition metals as catalysts.
