What is an atom primarily composed of?

An atom is predominantly made up of mostly empty space, which is a fundamental concept in understanding atomic structure. While atoms do contain subatomic particles, such as protons and neutrons residing in the nucleus and electrons in orbitals, the vast majority of the volume occupied by an atom is actually the space around the nucleus where the electron clouds exist. This means that when considering the physical structure of an atom, it is crucial to acknowledge that the area between the nucleus and the electron cloud contains little matter, leading to the conclusion that atoms are primarily composed of empty space.

In contrast, the other options specify various particles or combinations of them without recognizing the significant volume dedicated to the empty space within the atom. This distinction is important in fields such as chemistry and physics, as it influences how atoms interact and bond with one another.