Chemistry

Question Analysis
This question assesses the student's ability to distinguish between the mass number and the atomic mass, and to correctly identify the atomic number.

Key Concept Explanation
The mass number (A) is an integer that represents the total number of protons and neutrons in the nucleus.
The atomic mass is a precise value that includes the masses of protons, neutrons, and the binding energy.
The atomic number (Z) is the number of protons in the nucleus.

Step-by-step Solution
1. Identify the number of protons: 18.
2. Identify the number of neutrons: 22.
3. Calculate the mass number:

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