An element has eight protons, nine neutrons, and eight electrons. Its atomic number and atomic mass, respectively, are __________.

• A. 8 and 16
• B. 9 and 16
• C. 9 and 17
• D. 8 and 17

Answer: (D)

Verified step by step guidance

1. Identify the atomic number of an element, which is determined by the number of protons in the nucleus. In this case, the element has eight protons.
2. Recognize that the atomic number is the same as the number of protons, so the atomic number is 8.
3. Understand that the atomic mass (or atomic mass number) is the sum of protons and neutrons in the nucleus.
4. Calculate the atomic mass by adding the number of protons (8) and the number of neutrons (9): 8 + 9.
5. Conclude that the atomic mass is 17, so the atomic number and atomic mass are 8 and 17, respectively.