## Chemistry: The Central Science (13th Edition)

After filling the subshell $3s$, the electrons must move to the next lowest-energy subshell, the $3p$, not the $3d$.
$[Ne]3s^23d^5$ The problem here is quite similar to part a). After completely filling the orbital in subshell $3s$ with 2 electrons, the electrons must move to the next lowest-energy subshell, which is the $3p$ subshell, not the $3d$ one. Therefore, one correct electron configuration must be $[Ne]3s^23p^5$