Question

what is an atomic nucleus?
the outer part of an atom in which electrons move
the outer part of an atom in which neutrons move
the central part of an atom, composed of protons and neutrons
the central part of an atom, composed of protons and electrons

Explanation:

An atom has a nucleus. The nucleus is at the center. Protons (positive charge) and neutrons (no charge) are in the nucleus. Electrons (negative charge) move around the nucleus.

Answer:

the central part of an atom, composed of protons and neutrons