Answer:
Na has the most similar configuration.
Explanation:
Na electron configuration: 1s²2s²2p⁶3s¹ or [Ne] 3s₁
Mg electron configuration: 1s²2s²2p⁶3s² or [Ne] 3s²
Be electron configuration: 1s²2s² or [He] 2s²
This is because Na and Mg are right next to each other in the same period (horizontal).
<h2> refer the attachment</h2>
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Atomic number or the number of protons in the element.