Which of the following is a true statement about atomic nuclei?

• A. Atomic nuclei contain electrons.
• B. Atomic nuclei are always electrically neutral.
• C. All atomic nuclei have the same number of protons and neutrons.
• D. Atomic nuclei are composed of protons and neutrons.

Answer: (D)

Verified step by step guidance

1. Recall the basic structure of an atom: it consists of a nucleus and electrons surrounding it.
2. Understand that the atomic nucleus contains protons and neutrons, which are collectively called nucleons.
3. Recognize that electrons are not part of the nucleus; they orbit around the nucleus in electron clouds or shells.
4. Note that atomic nuclei are positively charged because they contain protons, and neutrons have no charge, so nuclei are not electrically neutral.
5. Realize that the number of protons defines the element, while the number of neutrons can vary, so not all nuclei have the same number of protons and neutrons.