Identify the element with the electron configuration [Rn] 7s² 5f⁸.

The electron configuration [Rn] 7s² 5f⁸ corresponds to an element located in the actinide series of the periodic table, specifically one of the heavy elements with nearby atomic numbers. To understand why this specific configuration denotes einsteinium, let’s analyze it more closely.

The notation [Rn] signifies the core electrons, which represent the noble gas radon. The subsequent 7s² indicates two electrons in the seventh energy level's s subshell. The 5f⁸ shows that there are eight electrons in the 5f subshell.

In the periodic table, einsteinium has an atomic number of 99, which is consistent with having a total of 99 electrons. When we derive the electron configuration:

• Counting from radon (86 electrons), adding 2 from the 7s subshell gives 88,

• Adding the 8 electrons from the 5f subshell totals 96,

• Therefore, einsteinium completes its electron configuration to 99 with the appropriate placement of electrons in the 7s and 5f subshells.

This configuration aligns perfectly with the known electron configuration for einsteinium, while the other options, namely californium