4.
Explanation
The order in which electrons are removed from orbitals in d-block elements is determined by the Aufbau principle, which follows the filling order of electrons based on increasing energy. This order is derived from the principles of quantum mechanics and does not directly align with Slater’s rules, which are used to estimate effective nuclear charge. However, Slater’s rules can provide some insight into the order of removal of electrons.
The Aufbau principle suggests that electrons are added to orbitals in order of increasing energy, filling lower energy levels before moving to higher ones. For d-block elements, the 4s orbital is filled before the 3d orbitals, following this order:
1. Fill 4s before 3d.
The reason for this is that the 4s orbital is typically at a lower energy level than the 3d orbitals. However, there are exceptions to this order for some transition metals, especially those in the middle of the transition series, due to electron-electron repulsions and subtle energy level differences.
Slater’s rules help estimate the effective nuclear charge experienced by an electron in a multi-electron atom. While these rules are useful for approximations, they do not directly dictate the order of filling orbitals. Slater’s rules consider the shielding effect of inner electrons, but they don’t account for the complex interactions of electron-electron repulsions and the detailed energy levels of orbitals.
In summary, the order of electron removal in d-block elements is primarily determined by the Aufbau principle, based on the increasing energy levels of the orbitals. While Slater’s rules can provide some context by estimating effective nuclear charge, they do not directly explain the filling order of electrons in d-block elements.