Which element has the electron configuration [Rn] 7s² 5f¹¹?

The electron configuration [Rn] 7s² 5f¹¹ indicates that the element has a total of 11 electrons in the 5f subshell, which identifies it as a member of the actinides or the f-block of the periodic table. The configuration begins with the noble gas radon (Rn), providing a stable electronic foundation. Following that, the filling of the 7s subshell with 2 electrons and the occupation of the 5f subshell with 11 electrons points directly towards einsteinium.

Einsteinium is known to have an atomic number of 99, which corresponds to the last electron being placed in the 5f orbital. This particular configuration is characteristic of einsteinium, as it possesses the necessary number of protons to account for the total electron count specified in the configuration.

While the other options like fermium, nobelium, and berkelium have different electron configurations attributed to their respective atomic numbers, einsteinium uniquely fits the configuration outlined. Each of these elements has differing counts of electrons in their f-orbitals and consequently do not match the specified configuration of [Rn] 7s² 5f¹¹. In summary, the electron configuration provided clearly