Which of the following part of atoms makes up more than 99.999999999% of an atom by volume?

The part of an atom that makes up more than 99.999999999% of its volume is the electron cloud. Here's a step-by-step explanation:

1. An atom is composed of three types of particles: protons, neutrons, and electrons.

2. Protons and neutrons are located in the nucleus of the atom, which is at the center.

3. Electrons, on the other hand, move around the nucleus in areas called electron clouds.

4. While the nucleus of an atom is incredibly dense, it is also incredibly small. The rest of the atom is mostly empty space where the electron clouds exist.

5. Therefore, even though the electrons themselves have very little mass, the space they occupy (the electron cloud) makes up more than 99.999999999% of the atom's volume.