Final answer:
The correct answer is that during ionization, 4s electrons are typically lost before 3d electrons because they possess higher energy, which is a result of the effective nuclear charge causing the 3d orbitals to become slightly lower in energy than the 4s orbitals in transition metals.
Step-by-step explanation:
The question at hand concerns the electronic configurations of atoms and specifically why 4s electrons are lost before 3d electrons during ionization. This phenomenon occurs because the 4s orbital is considered the outermost, highest energy orbital for transition metals, even though 4s is filled before 3d in neutral atoms. As atoms ionize, the energy levels adjust, and the 3d orbitals become slightly lower in energy due to the effective nuclear charge. Hence, 4s electrons, having higher energy, are removed before the 3d electrons when transition metals form cations. This removal pattern aligns with observed experimental results and theoretical calculations.
When examining the order of ionization energies as presented in various tables, one can note successive ionization energies increase, especially after the valence electrons are removed. This is due to the greater electrostatic attraction between the cation and remaining electrons, making it more difficult to remove subsequent electrons. The correct answer to the question is a) 4s electrons have higher energy than 3d electrons.