The space between the nucleus and the cloud of electrons in an atom is primarily occupied by empty space. The nucleus, which contains protons and neutrons, is located at the center of the atom and is surrounded by electron orbitals that form the electron cloud. The electron cloud is where the electrons are most likely to be found.
In terms of the matrix in which the atom exists, it is important to understand that atoms exist in a physical context of the surrounding environment. In a typical scenario, atoms are part of a material or a medium, such as a solid, liquid, or gas. The atoms interact with other atoms and molecules in their surroundings through various forces, such as electromagnetic forces.
However, it's worth noting that even in the absence of other atoms or molecules, there is still space between the nucleus and electrons within an atom. This space is not filled with any specific substance or matrix. It is simply empty space, where the probability of finding an electron is highest.
The concept of an atom existing within a matrix or medium becomes relevant when we consider the behavior of atoms in different environments, such as in a crystal lattice or a gas. The interaction between atoms and their surrounding environment plays a crucial role in determining the properties and behavior of materials.