AFOQT Practice Test

What does the atomic number of an element represent?

1. Number of neutrons

2. Number of protons

3. Number of electrons

4. Sum of protons and neutrons

The correct answer is: Number of protons

The atomic number of an element is defined as the total number of protons found in the nucleus of an atom of that element. This number uniquely identifies a chemical element and determines its position on the periodic table. Each element has a different atomic number, which is crucial for distinguishing one element from another. While the number of electrons in a neutral atom is equal to the number of protons and the sum of protons and neutrons gives the atomic mass, it is the number of protons that directly defines the identity of the element. Therefore, knowing the atomic number allows you to understand not just the element’s identity, but also its chemical behavior and how it interacts with other elements.