Final answer:
The nucleus of an atom is positively charged and contains most of the atom's mass, while electrons orbit in a much larger surrounding space, contributing to the atom's volume.
Step-by-step explanation:
The correct answer to the question about the atomic nucleus is b) It is positively charged and includes most of the atom's mass. The nucleus is indeed the positively charged region at the atom's center, containing protons and neutrons—collectively known as nucleons.
These subatomic particles are tightly packed together, with the protons carrying the positive charge and the neutrons being electrically neutral.
Although the nucleus is extremely small compared to the rest of the atom, it contributes virtually to all the atom's mass. Electrons, which are negatively charged, occupy the space outside the nucleus and make up most of the atom's volume.