Final answer:
The atom in the ground state that contains only one partially occupied orbital is Sodium (Na).
Step-by-step explanation:
The atom in the ground state that contains only one partially occupied orbital is Sodium (Na).
In the ground state of Sodium, the electron configuration is 1s²2s²2p6 3s¹. The 3s orbital is the lowest-energy subshell that is partially occupied.
Therefore, the correct answer is Na.