Which of the following is NOT found in the nucleus of an atom?

• A. Electron
• B. Both proton and neutron
• C. Neutron
• D. Proton

Answer: (A)

Verified step by step guidance

1. Recall the basic structure of an atom: it consists of a nucleus and an electron cloud surrounding the nucleus.
2. Understand that the nucleus contains protons and neutrons, which are collectively called nucleons.
3. Recognize that electrons are negatively charged particles that orbit the nucleus in electron shells or energy levels, not inside the nucleus.
4. Identify that since protons and neutrons are in the nucleus, and electrons are outside, the particle NOT found in the nucleus is the electron.
5. Therefore, the correct answer is 'Electron' because it is located outside the nucleus, unlike protons and neutrons.