Advertisements
Advertisements
प्रश्न
Why do transition elements show variable oxidation states ? In 3d series (Sc to Zn), which elements shows the maximum number of oxidation state and why ?
Advertisements
उत्तर
Transition elements have an incomplete set of d-orbitals in their penultimate shell. They have their valence electrons in (n−1)d- and ns-orbitals. Since there is very little energy difference between these orbitals, electrons from both the energy levels can be used for bond formation. As a result, transition elements exhibit variable oxidation states.
Valence shell electronic configuration for Mn (Z = 25): 3d5 4s2
In the 3d series, Mn has the maximum number of unpaired electrons present in the d-subshell (5 electrons). Hence, Mn exhibits the maximum number of oxidation states, ranging from +2 to +7.
APPEARS IN
संबंधित प्रश्न
What are interstitial compounds?
Which is a stronger reducing agent, Cr2+ or Fe2+ and why?
NF3 is possible, but NF5 is not. Why?
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.
Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:
(activation energy, Threshold energy, increased, lowered, partially, full, d-d transition, Benzoic acid, benzaldehyde)
Only those transition metal ions will be coloured which have ______ filled d-orbitals facilitating ______.
The spin magnetic moment of cobalt in the compound Hg [Co(SCN)4] is:-
The complex showing a spin-span magnetic moment of 2.82 B.M. is :-
Complete the following reaction and justify that it is a disproportionation reaction:
\[\ce{3MnO^{2-}4 + 4H^+ -> \underline{}\underline{}\underline{}\underline{} + \underline{}\underline{}\underline{}\underline{} + 2H2O}\]
Give a reason for the following:
Zinc, cadmium and mercury are considered as d-block elements but not regarded as transition elements.
Give a reason for the following:
Transition metals possess a great tendency to form complex compounds.
