The electron configuration [Rn] 7s² 5f¹² corresponds to which actinide element?

The electron configuration [Rn] 7s² 5f¹² indicates that this element has a foundation of Radon (Rn), which is a noble gas, and then adds two electrons in the 7s subshell and twelve electrons in the 5f subshell.

This placement suggests that the element is part of the actinide series, where the 5f orbitals are being filled. The configuration specifically denotes having twelve 5f electrons, which corresponds to the element Fermium (Fm). Fermium is the ninth element in the actinide series, having the atomic number 100.

Understanding the position and filling of the f orbitals is critical here. The actinides span from atomic number 89 (Actinium) to 103 (Lawrencium), with the f orbitals filling progressively as you move through this series. By recognizing that the 5f² and 5f¹² configurations correlate to the number of electrons filling the f subshells, one can accurately identify Fermium as the correct corresponding element for the given electron configuration.

The other elements listed have different numbers of electrons in their electron configurations, confirming that the configuration provided uniquely aligns with Fermium.