Кулькові моделі

Molecular Models

$$\underline{\text{Ball-and-Stick Models}}$$

What is a ball-and-stick model?

• A ball-and-stick model is a 3D representation of a molecule.

• Ball-and-stick models help us understand how each atom is bonded in a molecule. It uses a line or stick to represent the covalent bonds between atomic nuclei.

• The basis of the ball and stick model is Valence Bond Theory.

• They show sigma and pi bonding in molecules with multiple bonds.

• Ball-and-stick models also show relative bond lengths and ideal bond angles.

• They help us to visualize the molecular geometry and VSEPR shape.

• Physical models cannot show deviations from the ideal bond angle because they cannot model lone pairs.

• As seen above, the ball-and-stick models show a lot more detail compared to the lewis structures. The ball-and-stick models can show exactly how the atoms connect to each other in 3D space.

$$\underline{\text{Space-Filling Models}}$$

What is the space-filling model?

• The Space-filling model also provides a 3D representation of a molecule.

• It is "space-filled" due to the lack of visible lines connecting the atoms. Instead, the atoms are placed on each other (without using the visible bond lines).

• The sizes of the atoms are proportional to the atomic radii of that atom. For example, oxygen will look larger than hydrogen due to its larger radius.

• The Space-filling model is based on the Molecular Orbital Theory.

• Computational chemists use computer programs to create space-filling models. The program shows the molecule's electron cloud. So, we can predict reactivity, polarity, Van der Waal's forces, and solvent interactions.

• Biochemists apply space-filling models to study enzymes and proteins. It can help them study the electrostatic interactions of macromolecules. For example, they might model a ligand blocking an enzyme's binding site.

Modeling Chemicals With Space-Filling Models

Modeling Chemicals With Ball and Stick Models

(Video) Bonding Models and Lewis Structures: Crash Course Chemistry #24

by CrashCourse

In this video, CrashCourse Chemistry explains molecular models. He starts by defining a model as a representation. Next, he walks you through the history of chemistry. You'll learn that very famous scientists proposed outlandish models of chemical bonding. You'll also get a quick refresher on the Lewis dot model. Finally, he briefly touches on the quantum mechanical model.