Chemistry

Question Analysis
This question assesses the student's ability to calculate the mass number of an isotope given the number of protons and neutrons.

Key Concept Explanation
The mass number (A) is the sum of the number of protons (Z) and neutrons (N) in an isotope. It is a whole number and represents the total number of nucleons (protons and neutrons) in the nucleus.

Step-by-step Solution
1. Identify the number of protons (Z) and neutrons (N): Z = 11, N = 12.
2. Use the formula A = Z + N to find the mass nu...