Exactly how many distinct electrons are permanently integrated into the core electron cloud of an is — d and f Block Elements Chemistry Question

💡 Solution & Explanation

The atomic number of $Hf$ is $72$. Following the Aufbau principle and the periodic table structure, Xenon is the noble gas core ($Z=54$). The $6s$ orbital fills first ($2$ electrons), followed by the entire lanthanide series where the $4f$ subshell is completely filled with its maximum capacity of $14$ electrons. Thus, exactly $14$ electrons reside in the $4f$ subshell.