* not completed

. Which pattern of layers is found in cubic close-packed pattern:

ABABAB…. correct incorrect

AAAA…. correct incorrect

ABCABC… correct incorrect

* not completed

. The unit cell parameters that are used to define the shape and size of a crystal unit cell consist of:

angles between the sides of a unit cell correct incorrect

lengths of the parallel sides of a unit cell correct incorrect

angles between the sides and lengths of the sides of a unit cell. correct incorrect

* not completed

. A tetrahedral hole is formed by:

four touching spheres, three of which lie in one plane and the fourth is located in the dip between them; correct incorrect

six touching spheres, four of which lie in one plane and two other are located below and above the plane; correct incorrect

four touching, coplanar spheres. correct incorrect

* not completed

. Select the alloy type in which a totally new crystal structure is formed.

interstitial solid solution correct incorrect

intermetallic compounds correct incorrect

substitutional solid solutions correct incorrect

* not completed

. Which of the following statements correctly describes the NaCl structure type?

NaCl structure is composed of cubic close-packing of Cl^– anions with Na⁺ cations occupying every octahedral hole, this arrangement of cations and anions results in a 6:6 cation : anion coordination. correct incorrect

NaCl structure is composed of cubic close-packing of Cl^– anions with Na⁺ cations occupying every second tetrahedral hole, this arrangement of cations and anions results in a 4:4 cation : anion coordination. correct incorrect

NaCl structure is composed of hexagonal close-packing of Cl^– anions with Na⁺ cations occupying every tetrahedral hole, this arrangement of cations and anions results in a 6:6 cation : anion coordination. correct incorrect

* not completed

. Select the correct answer.

In the rutile (TiO₂) structure, each titanium atom is surrounded by three oxygen atoms and each oxygen atoms is surrounded by six titanium atoms. correct incorrect

In the rutile (TiO₂) structure, each titanium atom is surrounded by six oxygen atoms and each oxygen atoms is surrounded by three titanium atoms. correct incorrect

In the rutile (TiO₂) structure, each titanium atom is surrounded by two oxygen atoms. correct incorrect

* not completed

. Lattice enthalpies are calculated to establish the most stable crystal structure. Which is the correct statement?

Lattice enthalpies are always positive; the structure with the maximum value is the most stable. correct incorrect

Lattice enthalpies are always negative; the structure with the maximum value is the most stable. correct incorrect

Lattice enthalpies are always positive; the structure with the minimum value is the most stable. correct incorrect

* not completed

. Lattice enthalpies can be used to explain or predict:

only how stable the crystal lattice is correct incorrect

only the solubility of the lattice and the stability of its components' oxidation states correct incorrect

how stable the crystal lattice is, as well as the solubility of the lattice and the stability of its components' oxidation states correct incorrect

* not completed

. What types of elements commonly form nonstoichiometric compounds?

s-elements correct incorrect

some heavy p-block elements, as well as d- and f-ones correct incorrect

inert gases correct incorrect

* not completed

. A solid is an insulator if:

Enough electrons are present to fill a band completely and the energy gap before the next empty band is small. correct incorrect

Enough electrons are present to fill a band completely and the energy gap before the next empty band is equal to zero. correct incorrect

Enough electrons are present to fill a band completely and the energy gap before the next empty band is large. correct incorrect