Chemistry

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

Key Concept Explanation
The mass number (A) of an isotope is the sum of the number of protons (atomic number, Z) and the number of neutrons.

Step-by-step Solution
1. Identify the atomic number (Z) and the number of neutrons.
Atomic number (Z) = 20
Number of neutrons = 24
2. Calculate the mass number (A) using the formula: A = Z + number of neutrons.
A = 20 + 24 = ...