Electronic configuration of rhodium

Electrons in each shell

Rhodium has 45 electrons arranged as 2, 8, 18, 16, 1 across 5 shells, which is why it sits in period 5.

How to write it

Start from the previous noble gas core, written in square brackets, then add the remaining electrons in filling order. For rhodium that gives [Kr] 4d⁸ 5s¹.

Exception to the Aufbau rule. Filling orbitals in order would give 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d⁷, but the real configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁸ 5s¹ because the energies of the outer orbitals are very close, so the real ground state differs from the simple filling order.

Rhodium at a glance

Other elements in group 9