Which of the following elements has the same number of energy levels (principal shells) as nitrogen?

• A. Oxygen (O)
• B. Neon (Ne)
• C. Sodium (Na)
• D. Magnesium (Mg)

Answer: (B)

Verified step by step guidance

1. Recall that the number of energy levels (principal shells) in an atom corresponds to the period (row) of the element in the periodic table.
2. Identify the period of nitrogen (N) in the periodic table. Nitrogen is in period 2, which means it has 2 principal energy levels.
3. Check the periods of the given elements: Oxygen (O) is in period 2, Neon (Ne) is in period 2, Sodium (Na) is in period 3, and Magnesium (Mg) is in period 3.
4. Compare the periods of these elements to nitrogen's period. Elements in the same period have the same number of principal energy levels.
5. Conclude that Oxygen (O) and Neon (Ne), both in period 2, have the same number of energy levels as nitrogen.