What is the atomic number of all calcium isotopes?

• A. 22
• B. 20
• C. 40
• D. 18

Answer: (B)

Verified step by step guidance

1. Recall that the atomic number of an element is the number of protons in the nucleus of its atoms and is unique to each element.
2. Understand that isotopes of an element have the same atomic number but different mass numbers due to varying numbers of neutrons.
3. Identify that calcium is the element in question, and its atomic number corresponds to the number of protons in all its isotopes.
4. Look up or recall that the atomic number of calcium is 20, meaning every calcium isotope has 20 protons.
5. Conclude that regardless of the isotope (such as calcium-40 or others), the atomic number remains 20.