Q15: (a) Why do transition elements show variable oxidation states? Name the elements showing a maximum number of oxidation states among the first series of transition metals from Sc (Z = 21) to Zn (Z=30) Name the element which shows only +3 oxidation state (b) What is lanthanide contraction? Name an important alloy that contains some of the lanthanoid metals
Answer: (a) Elements with partially filled d orbitals are known as transition elements (also known as transition metals). The IUPAC defines transition elements as those that have a partially filled d subshell or those that can form stable cations with an incompletely filled d orbital. The electrical configuration of the transition element is (n-1)d5 ns1 or (n-1)d10 ns1. These elements have varying oxidation states because their valence electrons are in two different sets of orbitals, (n-1)d and ns. Both energy levels can be used to build bonds since the energy difference between them is so minimal. As a result, the oxidation states of transition elements vary. The d-subshell of Mn(Z-25) has the most unpaired electrons, thus it has a high oxidation state(+7). Scandium (Sc) is the sole element in these series that has a +3 oxidation state
