How many neutrons does a typical sodium (Na) atom have, given that its atomic number is 11 and its most common isotope has a mass number of 23?

• A. 13
• B. 11
• C. 12
• D. 23

Answer: (C)

Verified step by step guidance

1. Identify the atomic number of sodium (Na), which is given as 11. The atomic number represents the number of protons in the nucleus of an atom.
2. Recognize that the mass number of the most common isotope of sodium is given as 23. The mass number is the sum of protons and neutrons in the nucleus.
3. Use the formula to find the number of neutrons: \( \text{Number of neutrons} = \text{Mass number} - \text{Atomic number} \).
4. Substitute the given values into the formula: \( \text{Number of neutrons} = 23 - 11 \).
5. Perform the subtraction to find the number of neutrons in a typical sodium atom.