Which element corresponds to the electron configuration [Rn] 7s² 5f⁹?

The electron configuration [Rn] 7s² 5f⁹ corresponds to an element that has 9 electrons in the 5f subshell. The element that fits this description is Nobelium (No), which has an atomic number of 102.

To break down the electron configuration, the notation [Rn] indicates that the element has the same electron configuration as Radon, which accounts for the first 86 electrons. The addition of 7s² means that there are two electrons in the 7s subshell, bringing the total count to 88 electrons so far. The 5f subshell, with 9 electrons, adds 9 more to the total, yielding an atomic number of 97, but Nobelium also includes the filled 4f and subsequent electrons due to its position in the actinide series.

This helps clarify that Nobelium fits the given configuration because by adding up the electrons specified in the configuration [Rn] 7s² 5f⁹ (which totals 102 electrons), it directly corresponds to Nobleium and its known electron configuration.