Deck 4: The Structures of Simple Solids

Question 1

Find the correct statement:

A) Any given crystal lattice can belong to more than one crystal system because we can usually find more than one unit cell for a lattice.
B) One crystal system can have one and only one associated lattice type defined by the unit cell parameters.
C) We can find more than one unit cell for any given lattice, but the smallest, most symmetric one is considered the best choice.

Answer 1

C

Question 2

Where is a lattice point with fractional coordinates (0, ½, 0) located?

A) At the centre of the edge parallel to a axis.
B) At the centre of the edge parallel to b axis.
C) At the centre of the edge parallel to c axis.

Answer 2

B

Question 3

An octahedral hole is formed by:

A) two triangles of spheres rotated by 60 $\degree$ relative to each other and located on adjoining layers;
B) six spheres located across three adjoining layers of ABC pattern;
C) eight spheres in two squares from two AB layers rotated by 60 $\degree$ relative to each other.

Answer 3

two triangles of spheres rotated by 60 $\degree$ relative to each other and located on adjoining layers;

Question 4

What are nonclose-packed structures?

A) These structures have low space economy because the unit cells are separated for more than the length of one unit cell.
B) These structures have holes of larger volume than close packed structures, and therefore less efficient packing of the spheres.
C) These structures occur when different layers have different unit cells that cannot pack properly inside the structure.

Question 5

Which of the following statements correctly describes the CsCl structure type?

A) CsCl structure is composed of primitive cubic lattice of Cl^- anions with Cs⁺ cations occupying every cubic hole resulting in 8:8 cation : anion coordination.
B) CsCl structure is essentially body-centred cubic lattice with alternating Cl^- and Cs⁺ ions resulting in 8:8 coordination.
C) CsCl structure is composed of hexagonal close-packing of Cl^- anions with Cs⁺ cations occupying every octahedral hole, this arrangement of cations and anions results in a 6:6 cation : anion coordination.

Question 6

What is interstitial solid solution?

A) It is a material in which small atoms occupy holes in the structure of a metal without changing the original metallic structure.
B) It is a material formed between two metals in which atoms of one metal replace the atoms of the host metal without the change in the original structure.
C) It is a material with different structure than the structures of its components.

Question 7

Find the correct statement.

A) The radii of ions of the same charge increase across a period and decrease down a group.
B) If an element can form cations with different charge numbers, then for a given coordination number its ionic radius decreases with increasing charge number.
C) If one ion occurs in environments with different coordination numbers, then its measured radius decreases as the coordination number increases.

Question 8

Find the correct statement.

A) Lattice enthalpy is the standard molar enthalpy change accompanying the formation of a liquid phase from the phase.
B) Born-Mayer equation tells us that the lattice enthalpy decreases with decrease in interionic distance in the lattice.
C) Lattice enthalpy can be determined using Born-Haber cycle and available experimental thermodynamic data.

Question 9

What is Schottky defect?

A) It is a defect in which cation and anion swap their normal locations in the structure.
B) It is a point defect in which an atom or ion is missing from its normal site in the structure.
C) It is a defect that moves a cation or an anion from its original location in the structure into a neighbouring, otherwise unoccupied hole.

Question 10

A solid is an insulator if:

A) Enough electrons are present to fill a band completely and the energy gap before the next empty band is small.
B) Enough electrons are present to fill a band completely and the energy gap before the next empty band is equal to or less than zero.
C) Enough electrons are present to fill a band completely and the energy gap before the next empty band is large.