What is the highest energy orbital in a square planar configuration?

In a square planar configuration, the geometry is such that the central atom is surrounded by ligands at the corners of a square plane. This arrangement affects the splitting of the d orbitals due to ligand interactions, specifically through the crystal field theory.

In a square planar system, the d orbitals split into different energy levels due to the specific orientation of the ligands. The higher energy orbital in this setup is the dx2-y2 orbital. This orbital is aligned with the axes along which the ligands are positioned (the x and y axes), leading to increased electron repulsion due to the presence of ligands. This repulsion raises the energy level of the dx2-y2 orbital above that of the other d orbitals in the configuration.

The other options, such as the yz, zx, and z2 orbitals, do not interact with the ligands in the same manner as dx2-y2. The yz and zx orbitals, which are oriented between the axes, experience less direct repulsion and hence are lower in energy. The z2 orbital, while it may have some interaction, is generally not positioned in the path of ligand electron clouds in a square planar setup and does not reach the same energy level as dx2-y