Which subatomic particle takes up most of the space of an atom?
Rawboner either misread the question or is misleading you. All atoms are made up of a heavy but almost zero volume nucleus and electrons which orbit the nucleus at a comparatively large distance.The whole of the volume (space) of an atom is made up of these electrons. Compare the solar system. Although the sun (nucleus) is very heavy it occupies much less space than the planets (electrons) which orbit billions of kilometers away from it. Most of the space in the solar system is described by the planets’ orbits. In fact the nucleus occupies only 1/1,000,000,000,000th of the space of the atom. To visualise this imagine an atom the size of the earth; the nucleus would be only a few metres across.
