Question

Significance of ionisation energy in determining the stable oxidation state of dblock

Answer 1

As the number of protons increase within a period (or row) of the periodic table, the first ionization energies of the transition-metal elements are relatively steady, while that for the main-group elements increases. The effective nuclear charge mirrors and may explain the periodic trends in the first ionization energies of the transition-metal and main-group elements. The differing periodic trends in the effective nuclear charge are due to a greater increase in shielding in the transition-metal elements than in the main-group elements. The difference in shielding is due to the entry of electrons into an inner-shell orbital for the transition-metal elements, while electrons enter an outer-shell orbital for the main-group elements.