The two elements that have the same number of energy levels with electrons in them are neon and sodium.
Neon (Ne) has 2 energy levels, while sodium (Na) also has 3 energy levels, but the question referring to the total number can be a little misleading. Both would have 3 energy levels in terms of their respective electron configuration being similar to energy shells.
However, based on typical configuration for energy levels:
- Neon has a configuration of 1s² 2s² 2p⁶ (2 energy levels)
- Sodium has a configuration of 1s² 2s² 2p⁶ 3s¹ (3 energy levels)
So, if strictly adhering to traditional energy levels noted in this question and looking for only those that share the exact number of filled shells, the best answer among the options you provided is krypton and neon, as both have filled shells within their respective levels.
If you're looking directly at complete shells in terms of valence and filled configurations.
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