What is the electronic configuration (shell by shell) of the element Na (atomic number 11)?

Answer and explanation

Correct answer: A. 2,8,1

  1. Step 1: Fill the shells in order: 2 in the first, 8 in the second, 8 in the third. Step 2. 11 electrons give 2,8,1. Answer: 2,8,1. Why not the others: 2,8,2 is what you get if you count one or two electrons too many or too few. 2,8 is what you get if you count one or two electrons too many or too few. 2,8,3 is what you get if you count one or two electrons too many or too few.

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