Ace the ACS Chemistry Challenge 2025 – Ignite Your Inner Scientist!

The volume composition of an atom is best described as mostly empty space. This understanding stems from the structure of an atom, where the nucleus, composed of protons and neutrons, occupies a very small fraction of the total volume of the atom. The nucleus is surrounded by a cloud of negatively charged electrons distributed over a relatively large area compared to the nucleus itself.

The empty space refers to the regions where these electrons exist, which can be visualized as orbitals rather than fixed paths. As a result, there is a significant amount of volume in an atom that does not contain any matter in the form of protons, neutrons, or electrons densely packed together. Rather, the electrons are found in a probabilistic distribution around the nucleus.

The alternatives describe aspects of atomic structure inaccurately. For instance, while electrons occupy regions around the nucleus, they do not constitute a volume filled with matter as suggested. Solid matter implies a structure that is tightly packed, which does not accurately represent atomic structure. Additionally, the volume filled with protons would also be misleading since protons are located in the small, central nucleus, again highlighting that the majority of the atom's volume is indeed empty space.