Which is one piece of information that the atomic number (9) gives about an atom of fluorine?

• A. It tells the number of electrons in the outermost shell.
• B. It tells the number of neutrons in the nucleus.
• C. It tells the number of protons in the nucleus.
• D. It tells the atomic mass of the atom.

Answer: (C)

Verified step by step guidance

1. Understand that the atomic number of an element is a fundamental property that defines the element itself.
2. Recall that the atomic number is equal to the number of protons in the nucleus of an atom.
3. Recognize that the number of protons determines the identity of the element (for example, fluorine always has 9 protons).
4. Note that the atomic number does not directly tell the number of neutrons or electrons in the outermost shell, nor does it give the atomic mass.
5. Therefore, the atomic number (9 for fluorine) specifically tells us the number of protons in the nucleus of the atom.