The electronic configuration of the element with atomic number 78 is:

Step-by-step solution

The atomic number of the element is Z = 78 . This element is Platinum (Pt). The noble gas preceding atomic number 78 is Xenon (Xe), which has an atomic number of 54. The electronic configuration follows the Aufbau principle, filling the 6s , 4f , and 5d orbitals. The expected configuration based on the order of energy levels would be [Xe] 4f¹⁴ 5d^8 6s^2 . However, due to the stability associated with the filled d -subshell and the specific energy gaps between the 5d and 6s orbitals in heavy transition metals, Plati