Question 1

Which of the following statements describe properties of metallic solids? Please select all that apply.

Accepted Answer

Metallic solids are known for their good thermal conductivity, high density, and good electrical conductivity. They are not typically brittle.

Question 2

Ionic solids are held together with __________ interactions.

Accepted Answer

electrostatic

Question 3

Match the material with the bonding type.
-platinum (Pt)

Accepted Answer

Platinum (Pt) is a transition metal which typically exhibits metallic bonding, where there is a delocalization of electrons throughout the metal lattice.

Question 4

Match the material with the bonding type. -N₂O

Accepted Answer

N₂O is a molecular compound, meaning it is held together by covalent bonds.

Question 5

Match the material with the bonding type.
-S

Accepted Answer

Sulfur has a covalent bonding type, where the atoms share electrons between them to form a chemical bond.

Question 6

Match the material with the bonding type. -SrF₂

Accepted Answer

The presence of Sr (a metal) and F (a nonmetal) indicates that the material has ionic bonding.

Question 7

A crystalline solid demonstrates long-range order which persists over distances much greater than the bond length between the atoms. It is possible to predict the position of every atom from those given in the unit cell.

Accepted Answer

This statement accurately describes one of the key characteristics of a crystalline solid.

Question 8

The structure of C₆₀ is analogous to the stitching on a European football and is shown in the diagram below. Each carbon lies on the surface of a sphere and the carbon is sp³hybridized?

Accepted Answer

The answer of The structure of C₆₀ is analogous to...

Question 9

Silicon dioxide exists as different polymorphs e.g. quartz and cristobalite. When silicon dioxide is melted and quenched (rapidly cooled), it forms an _______ structure known as a glass.

Accepted Answer

The answer of Silicon dioxide exists as different polymorphs e.g....

Question 10

A magnetic levitation train uses the Meissner effect to propel the train along magnetic rails. Which of these facts relating to superconductors are true. Please select all that apply.

Accepted Answer

A) Superconductors are indeed diamagnetic, meaning they will repel a magnetic field.
B) This statement is not true. For a material to exhibit superconductivity, it must be below its critical temperature. Above this temperature, the material loses its superconductivity and will not exhibit the Meissner effect.
C) This statement is true. Electrons in a superconductor are paired up, known as Cooper pairs. These pairs can move through the lattice without resistance, giving rise to superconductivity.
D) This statement is also true. The Meissner effect occurs when a superconductor expels any magnetic field from its interior when it is below its critical temperature.

Question 11

The structure with repeat sequence ABCCABCCABCCABC is close-packed.

Accepted Answer

The sequence ABCCABCCABCCABC is not a close-packed structure. Close-packed structures typically involve sequences like ABCABC (face-centered cubic) or ABAB (hexagonal close-packed), where each layer is efficiently packed to maximize space utilization.

Question 12

A body centred cubic unit cell is close-packed.

Accepted Answer

A body-centered cubic (BCC) unit cell is not considered close-packed because it has a lower packing efficiency (68%) compared to face-centered cubic (FCC) or hexagonal close-packed (HCP) structures, which have a packing efficiency of 74%.

Question 13

$\beta$-tungsten crystallises with a body centred cubic structure where the length of the unit cell is 3.150 Å. Use the diagram to calculate the radius of a tungsten atom. (Hint: The radius of the atom is just half the distance between the two closest atoms.)

Accepted Answer

In a body centered cubic structure, the atoms are arranged in a way that each atom has eight neighboring atoms. The distance between the two closest atoms is equal to the body diagonal of the cube, which can be calculated using the length of the unit cell (a) as follows:

body diagonal = a*sqrt(3)

= 3.15 Å * sqrt(3)

= 5.454 Å

The radius of a tungsten atom is half of the body diagonal, which is :

radius = 5.454 Å / 2

= 2.727 Å

Therefore, the radius of a tungsten atom is 1.346 Å (option C).

Question 14

A lattice point on the edge of a cubic unit cell is worth one quarter of a lattice point

Accepted Answer

A lattice point on the edge of a cubic unit cell is shared by two unit cells, so it is worth half of a lattice point.

Question 15

A semiconductor has which of the following properties? Please select all that apply.

Accepted Answer

The answer of A semiconductor has which of the following...

Question 16

What is the formula of a compound based on cubic close packing where one quarter of the tetrahedral holes (T) are filled in a lattice made of lattice points of type A. What is the coordination number of the filled holes and the lattice points? Please select all that apply.

Accepted Answer

The answer of What is the formula of a compound...

Question 17

Li₂O crystallises with the antifluorite structure where the positions of the cations and anions are in the opposite positions to the structure observed for fluorite. What are the coordination numbers of the lithium and oxygen ions?

Accepted Answer

In the antifluorite structure, the anions occupy the tetrahedral sites and the cations occupy the octahedral sites. Therefore, the coordination number of lithium (cation) is four and the coordination number of oxygen (anion) is eight.

Question 18

Lattice point counting for sphalerite shows that the structure contains ___ Zn/S ions.

Accepted Answer

The answer of Lattice point counting for sphalerite shows that...

Question 19

The coordination number of iodine in cadmium iodide is six.

Accepted Answer

The answer of The coordination number of iodine in cadmium...

Question 20

There is no structural analogue of CaF₂ in hexagonal close packing (fill all tetrahedral holes).

Accepted Answer

In hexagonal close packing, all tetrahedral holes are occupied by atoms of a different element. However, CaF₂ does not have a structural analogue in hexagonal close packing as there is no known element or compound that can fill the tetrahedral voids in the same way as the given molecule.

Quiz 6: Solids

Which of the following statements describe properties of metallic solids? Please select all that apply.

Ionic solids are held together with __________ interactions.

Match the material with the bonding type. -platinum (Pt)

Match the material with the bonding type. -N2O

Match the material with the bonding type. -S

Match the material with the bonding type. -SrF2