Question

(i) Why do transition elements show variable oxidation states?
(ii) Name the element showing maximum number of oxidation states among the first series of transition metals from $Sc(Z=21)$ to $Zn(Z=30)$.
(iii) Name the element which shows only $+3$ oxidation state.
(iv) What is lanthanoid contraction? Name an important alloy which contains some of the lanthanoid metals.

Answer 1

1.Transition elements show variable state oxidation in their compounds because there is a very small energy difference in between (n-1)d and ns orbitals. As a result, electrons of (n-1)d orbitals as well as ns-orbitals take part in bond formation.

2. Mn(Z-25) has the maximum number of unpaired electrons present in the d-subshell so it shows maximum oxidation states(+7)

3. Sc only exhibits a +3 oxidation state in these series.

4.The lanthanide contraction, i.e. the reduction in size of the $L{n}^{3+}$ ion from $L{a}^{3+}$(103 pm) to $L{u}^{3+}$(86.1 pm), is often explained by the poor shielding of the 5s and 5p electrons by the 4f electrons.An alloy is a solid solution of two or more elements in a metallic matrix. It can either be a partial solid solution or a complete solid solution. Alloys are usually found to possess different physical properties than those of the component elements.An important alloy of lanthanoids is Mischmetal. It contains lanthanoids (94−95%), iron (5%), and traces of S, C, Si, Ca, and Al.