D Block Elements 3 Flashcards
KMnO4 is diamagnetic
There are no unpaired electrons
In the series Sc(Z = 21) to Zn (Z = 30), the enthalpy of atomisation of zinc is the lowest.
zinc (3d104s2 configuration), electrons from the 3d-orbitals are not involved in the formation of metallic bonds since all the orbitals are completely filled. There for Zn has weak metallic bond and low enthalpy of atomization.
Which element of the 3d series of the transition metals exhibits the largest number of oxidation states and why?
Manganese (Z = 25) shows maximum number of oxidation states. 3d54s2 configuration has maximum number of unpaired electrons.
Why is the highest oxidation state of a metal exhibited by its fluoride and oxide only?
Due to small size and very high electronegativity fluorine and
oxygen .
Which is a stronger reducing agent Cr2+ or Fe2+ and why?
Thus, Cr2+ is a stronger reducing agent than Fe2+ because it more readily oxidizes to Cr3+, which has a stable half-filled electron configuration
Explain why Cu+ ion is not stable in aqueous solutions?
Hydration enthalpy of of Cu2+(aq) is much higher than that of Cu+(aq) and hence it compensates for the 2nd IE of Cu.
Cu+ ions are unstable in aqueous solution and undergo
disproportionation as follows :
2 Cu+ —–> Cu2+ + Cu
Why are Mn2+ compounds more stable than Fe2+ towards oxidation to their+3 state?
Electronic configuration of Mn2+ is 3d5. This is a half-filled configuration and hence stable. Electronic configuration of Fe2+is 3d6. It can lose one electron easily
to achieve a stable configuration 3d5
.
Explain briefly how+2 state becomes more and more stable in the first half of the first row transition elements with increasing
atomic number?
After losing 2 electrons from s-orbitals, the 3d-orbital gets gradually occupied with increase in atomic number. Since the number of unpaired electrons in 3d orbital increases, the stability of the cations
(M2+) increases from Sc2+ to Mn2+.
Predict which of the following will be coloured in aqueous solution?
Ti3+, V3+, Cu+, Sc3+, Mn2+, Fe3+, Co2+.
Those ions which have incomplete d-orbitals will be colored. The ions with either empty or filled d-orbitals are colourless.
The coloured ions among the given list are :
Ti3+(3d1), V3+(3d2), Mn2+(3d5), Fe3+(3d5), Co2+ (3d7) Sc3+ (3d°) and Cu+ (3d10) ions are colourless.
Cobalt (II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidised
Co (III) has .greater tendency to form coordination complexes than Co (II) due to higher charge and smaller size. Hence, in the presence of ligands, Co (II) changes to Co (III), i.e., is easily oxidized.
Which metal in the first transition metal series exhibits +1 oxidation state most frequently and why?
Cu with configuration [Ar] 4s13d10 exhibits +1 oxidation state and forms Cu+ ion because it acquires a stable configuration of d orbitals (3d10).
Why are Mn2+ compounds more stable than Fe2+ towards oxidation to their +3 state?
Electronic configuration of Mn2+ is [Ar] 18 3d5 Mn in (+2) state has a half-filled stable configuration.
Fe2+ : [Ar] 18 3d6 has partially filled subshells, and can undergo oxidation easily to form stable 3d5 configuration.
Compare the chemistry of actinoids with that of lanthanoids with special reference to Electronic configuration:
The general electronic configuration of lanthanoids is 4f1-14 5d0-1 6s2
.
The general electronic configuration of actinoids is 5f1-14 6d0-1 7s2
Compare the chemistry of actinoids with that of lanthanoids with special reference to Oxidation state:
Lanthanoids show only less number of oxidation states, +2,+3, +4 due to large energy gap between 4f, 5d and 6s subshells. Actinoids show large number of oxidation states because of small energy gap between 5f, 6d and 7s subshells.
Compare the chemistry of actinoids with that of lanthanoids with special reference to Atomic and ionic size:
Actinoid contraction is greater than
lanthanoid contraction due to poor shielding effect of 5f electrons compared to 4f electrons.
