electron configuration of Pd

The atomic number of Pd is 46. According to aufbau rule, the electronic configuration is expected to be [Kr] 4d8 5s2. Completely-filled degenerate orbitals would exhibit extra stability. Since the energy levels of 4d and 5s subshells are close, the two 5s electrons would rather locate in the 4d shell in order to exhibit extra stability. Therefore, the actual ground state electronic configuration of Pd is [Kr] 4d10.