(i) The first transition metal Scandium exhibits only +3 oxidation state, but all other transition elements exhibit variable oxidation states by loosing electrons from (n-1)d orbital and ns orbital as the energy difference between them is very small. At the beginning of the series, +3 oxidation state is stable but towards the end +2 oxidation state becomes stable. The first and last elements show less number of oxidation states and the middle elements with more number of oxidation states
(ii) For example, the first element Sc has only one oxidation state +3; the middle element Mn has six different oxidation states from +2 to +7. The last element Cu shows +1 and +2 oxidation states only.

Elemental copper is more stable than Cu²⁺. The electronic configuration of copper is 3d¹⁰ 4s¹ completely filled 3d orbital with stable configuration.
But Cu²⁺ has configuration as 3d⁹. Hence \(\mathrm{E}_{\mathrm{M}^{2+} / \mathrm{M}}^{0}\) value is positive for Cu²⁺.

Zirconium is a 4d element and Hafnium is a 5d element. There is an unexpected observation in the atomic radius of 5d elements which have nearly the same atomic radius as that of corresponding 4d elements. This is due to lanthanoid contraction. Hence they exhibit similar properties.

La(OH)₃ is more basic than Lu(OH)₃. Due to lanthanide contraction, the size of Ln³⁺ ions decreases regularly with increase in atomic number. According to Fajan's rule, decrease in size of Ln³⁺ ions decreases the basic character between Ln³⁺ and OH^- ion in Ln(OH)₃. So La(OH)₃ is more basic than Lu(OH)₃.

Chromium (24), the electronic configuration is 3d⁵4s¹. It ready to lose its outer most electron (4s¹) to get exactly half-filled stable electronic configuration. The electronic configuration of Zinc is 3d¹⁰4s².ie., It has completely filled stable configuration. From this configuration, the removal of 1e^- from 4s orbital is very difficult & it required more ionisation enthalpy. Due to this reason Zn has higher first Ionisation enthalpy (1.E₁) than that of chromium.