4
AssignmentMultiple Choice

Atomic Numbers and Electron Configurations

Question 4 • *26-27 CFISD TX-Chemistry A CR

Which is the correct electron configuration for sodium (Na)?

Answer
A
1s22s22p62d1
B
1s22s22p63s1
C
1s22p63d3

Explanation

Sodium has 11 electrons. Filling orbitals in order gives 1s² (2 electrons), 2s² (2), 2p⁶ (6), and then 3s¹ (1), for a total of 11. Therefore, the correct configuration is B) 1s²2s²2p⁶3s¹.

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