Which of the following is true of both chlorine and sodium atoms?

• A. Both are noble gases.
• B. Both have the same number of valence electrons.
• C. Both contain protons, neutrons, and electrons.
• D. Both have atomic numbers greater than 20.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the nature of atoms. Every atom, regardless of the element, is composed of three fundamental particles: protons, neutrons, and electrons. Protons and neutrons reside in the nucleus, while electrons orbit the nucleus.
2. Step 2: Analyze the options given. The first option states both chlorine and sodium are noble gases. Recall that noble gases are elements in Group 18 of the periodic table, characterized by full valence shells. Chlorine and sodium are not noble gases; chlorine is a halogen (Group 17), and sodium is an alkali metal (Group 1).
3. Step 3: Consider the valence electrons. Sodium has 1 valence electron (in the 3s orbital), while chlorine has 7 valence electrons (in the 3s and 3p orbitals). Therefore, they do not have the same number of valence electrons.
4. Step 4: Check the atomic numbers. Sodium has an atomic number of 11, and chlorine has an atomic number of 17. Both are less than 20, so the statement about atomic numbers greater than 20 is false.
5. Step 5: Conclude that the only universally true statement for both atoms is that they contain protons, neutrons, and electrons, as this is a fundamental property of all atoms.