Van der Waals Forces Quiz

What is a characteristic property of crystalline materials?

What type of bonding is described as temporary and fluctuating with time?

Which type of materials lack a crystalline structure?

Which term describes molecules that have a permanent dipole moment?

What model illustrates atoms as spheres touching each other at their closest points?

On a bonding tetrahedron, what is located at each vertex to represent the four bonding types?

Which crystal structure has atoms located at each of the cube's corners and center of its faces?

What term is used for atomic bonds that are mixtures of two or more extreme types of bonds?

What is the term used to represent small repeat entities in crystal structures?

What is the coordination number for face-centered cubic crystal structures?

Which material class is associated with metallic bonding?

What type of bonding is found in molecular solids?

Crystal Structure and Properties

Crystal structure affects material properties, such as brittleness (e.g., magnesium and beryllium) vs. ductility (e.g., gold and silver)
Noncrystalline materials (e.g., ceramics and polymers) are often optically transparent, whereas crystalline forms are opaque or translucent

Crystalline and Non-Crystalline Materials

Crystalline materials have long-range atomic order, with atoms arranged in a repetitive three-dimensional pattern
Non-crystalline materials lack long-range atomic order and exhibit no crystalline structure

Polycrystalline Materials

Exhibit long-range order due to the formation of multiple small crystalline regions or grains, each with its own crystallographic orientation

Atomic Hard-Sphere Model

Represents atoms as spheres that touch each other at their closest points, illustrating nearest-neighbor interactions

Lattice and Unit Cells

Lattice refers to a three-dimensional array of points coinciding with atom positions (or sphere centers)
Unit cells are small repeat entities that make up the crystal structure, often subdivided for convenience

Face-Centered Cubic (FCC) Crystal Structure

Common crystal structure found in many metals, characterized by a cubic unit cell with atoms at corners and face centers
Important characteristics include coordination number and atomic packing factor (APF)

Bonding Types

Ionic, covalent, metallic, and van der Waals bonding types exist, and many real materials exhibit mixed bonding
Bonding tetrahedron represents these bonding types, with mixed-bond types on the edges
Correlations exist between bonding type and material class (e.g., polymers: covalent, metals: metallic, ceramics: ionic/mixed ionic-covalent)

Test your knowledge on Van der Waals forces, which are weak intermolecular forces between molecules or atoms caused by temporary or permanent dipoles. Learn about the attraction between molecules due to induced and permanent dipole moments.