What is "space-filling model"

alt. (context chemistry English) A type of three-dimensional molecular model, where the atoms are represented by spheres whose radius are proportional to the radii of the atoms, and whose center-to-center distances are proportional to the distances between the atomic nucleus, all in the same scale. n. (context chemistry English) A type of three-dimensional molecular model, where the atoms are represented by spheres whose radius are proportional to the radii of the atoms, and whose center-to-center distances are proportional to the distances between the atomic nucleus, all in the same scale.

In chemistry, a space-filling model, also known as a calotte model, is a type of three-dimensional (3D) molecular model where the atoms are represented by spheres whose radii are proportional to the radii of the atoms and whose center-to-center distances are proportional to the distances between the atomic nuclei, all in the same scale. Atoms of different chemical elements are usually represented by spheres of different colors.

Space-filling calotte models are also referred to as CPK models after the chemists Robert Corey, Linus Pauling, and Walter Koltun, who over a span of time developed the modeling concept into a useful form. They are distinguished from other 3D representations, such as the ball-and-stick and skeletal models, by the use of the "full size" space-filling spheres for the atoms. They are useful for visualizing the effective shape and relative dimensions of the molecule, and the shapes of surface a given static conformer might present. On the other hand, these models mask the chemical bonds between the atoms, and make it difficult to see the structure of the molecule that is obscured by the atoms nearest to the viewer in a particular pose. For this reason, such models are of greater utility if they can be used dynamically, especially when used with complex molecules (e.g., see the greater understanding of the molecules shape given when the THC model is clicked on to rotate).