Which statement best describes the relationship between the atomic number and the number of protons in an atom?

• A. The atomic number is always greater than the number of protons in an atom.
• B. The atomic number is equal to the sum of protons and neutrons in an atom.
• C. The atomic number is unrelated to the number of protons in an atom.
• D. The atomic number is equal to the number of protons in the nucleus of an atom.

Answer: (D)

Verified step by step guidance

1. Understand that the atomic number (symbolized as \(Z\)) is a fundamental property of an element that defines the identity of an atom.
2. Recall that the atomic number corresponds to the number of protons in the nucleus of an atom, which determines the element's position on the periodic table.
3. Recognize that the number of protons is unique for each element, so the atomic number directly equals the number of protons.
4. Note that the atomic number is not related to the number of neutrons or electrons, and it is not a sum of particles but specifically the count of protons.
5. Therefore, the correct relationship is: Atomic number \(Z\) = Number of protons in the nucleus of an atom.