Two solids are shown below. One is a semiconductor and one is an insulator. Which one is which? Explain your reasoning.

For each of the two-dimensional structures shown here (a) draw the unit cell (i)

(ii)

Shown here are sketches of two processes. Which of the processes refers to the ductility of metals and which refers to malleability of metals? (a)

(b)

(b) What is the coordination number of each cannonball in the interior of the stack?

Which arrangement of cations (yellow) and anions (blue) in a lattice is the more stable? Explain your reasoning. (a)

(b)

Which of these molecular fragments would you expect to be more likely to give rise to electrical conductivity? Explain your reasoning. (a)

(b)

The electronic structure of a doped semiconductor is shown here. (c) Which region of the diagram represents the band gap?

Shown here are cartoons of two different polymers. Which one would have the higher melting point?

The accompanying image shows photoluminescence from four different samples of CdTe nanocrystals, each embedded in a polymer matrix. The photoluminescence occurs because the samples are being irradiated by a UV light source. The nanocrystals in each vial have different average sizes. The sizes are 4.0, 3.5, 3.2, and 2.8 nm. (a) Which vial contains the 4.0-nm nanocrystals?

Silicon is the fundamental component of integrated circuits. Si has the same structure as diamond. (a) Is Si a molecular, metallic, ionic, or covalent-network solid?

Silicon is the fundamental component of integrated circuits. Si has the same structure as diamond. (b) Silicon readily reacts to form silicon dioxide, SiO2, which is quite hard and is insoluble in water. Is SiO2 most likely a molecular, metallic, ionic, or covalent-network solid?

What kinds of attractive forces exist between particles (atoms, molecules, or ions) in (a) molecular crystals?

What kinds of attractive forces exist between particles (atoms, molecules, or ions) in (d) and metallic crystals?

Which type (or types) of crystalline solid is characterized by each of the following? (a) High mobility of electrons throughout the solid;

Which type (or types) of crystalline solid is characterized by each of the following? (b) softness, relatively low melting point;

Which type (or types) of crystalline solid is characterized by each of the following? (c) high melting point and poor electrical conductivity;

Which type (or types) of crystalline solid is characterized by each of the following? (d) network of covalent bonds.

Indicate the type of solid (molecular, metallic, ionic, or covalent-network) for each compound: (c) Ta2O5 (melting point, 1872°C)

You are given a gray substance that melts at 700 °C; the solid is a conductor of electricity and is insoluble in water. Which type of solid (molecular, metallic, covalent-network, or ionic) might this substance be?

(a) Draw a picture that represents a crystalline solid at the atomic level.

(b) Now draw a picture that represents an amorphous solid at the atomic level.

Two patterns of packing for two different circles of the same size are shown here. For each structure (b) determine the angle between the lattice vectors, g, and determine whether the lattice vectors are of the same length or of different lengths; (i)

(ii)

Two patterns of packing two different circles of the same size are shown here. For each structure (c) determine the type of two-dimensional lattice (from Figure 12.4). (i)

(ii)

Imagine the primitive cubic lattice. Now imagine grabbing the top of it and stretching it straight up. All angles remain 90. What kind of primitive lattice have you made?

Which of the three-dimensional primitive lattices has a unit cell where none of the internal angles is 90? (a) Orthorhombic, (b) hexagonal, (c) rhombohedral, (d) triclinic, (e) both rhombohedral and triclinic.