Copper is an element with 29 protons in its nucleus. What is the atomic number of copper?

• A. 47
• B. 29
• C. 18
• D. 63.5

Answer: (B)

Verified step by step guidance

1. Understand that the atomic number of an element is defined as the number of protons in the nucleus of an atom of that element.
2. Identify from the problem that copper has 29 protons in its nucleus.
3. Recall that the atomic number is equal to the number of protons, so the atomic number of copper is 29.
4. Note that the other numbers given (47, 18, 63.5) correspond to other properties: 47 is the atomic number of silver, 18 is the atomic number of argon, and 63.5 is the approximate atomic mass of copper.
5. Therefore, the atomic number of copper is 29 because it matches the number of protons in its nucleus.