Aufbau diagram of actinium

actinium | Aufbau diagram

Build the ground-state orbital diagram for: actinium (Ac) Plan: • Look up the abbreviated (condensed) ground electronic configuration. • Use the electronic configuration to identify the outermost electrons. • Determine the energetic ordering of atomic orbital subshells. • Use the following representations: a gray rectangle for an atomic orbital, an up arrow for an alpha (spin-up) spin state and a down arrow for a beta (spin-down) spin state. • Follow the Pauli exclusion principle by representing the first electron in each atomic orbital with an alpha spin state and the second electron with a beta spin state. • Place electrons into orbitals following the Aufbau principle and Hund's rule. The abbreviated ground electronic configuration for actinium is: [Rn]7s^26d^1 Electrons in atomic orbitals outside of the radon core, [Rn], are the outermost electrons: 7s^26d^1 Atomic orbital energy usually increases from 1s to 8s in the following order: The orbital filling order in actinium is an exception to the usual energetic ordering of atomic orbitals: This reflects a change in the atomic orbital energies for actinium rather than a violation of the Aufbau principle. Place two electrons as an alpha-beta pair into the 7s orbital: 7s Follow Hund's rule by placing one alpha electron into one of the five 6d orbitals: Answer: | | 6d 7s