(Part 2) Unit 3. The Chemistry of Engineering Materials

Question 1

Types of Unit Cell

Answer 1

1. Simple Cubic
2. Body-Centered Cubic Unit Cell (BCC)
3. Face-centered Cubic Unit Cell (FCC)

Question 2

only one lattice point at each corner of the cube-shaped unit cell

Answer 2

Simple Cubic Crystal Structure

Question 3

mark the position of either a single atom, or the same group of atoms which is repeated across the lattice.

Answer 3

Simple Cubic Crystal Structure

Question 4

Close-packed directions are cube edges.

Answer 4

Simple Cubic Crystal Structure

Question 5

Very few examples of simple cubic lattices are known ___

Answer 5

(alpha– polonium)

Question 6

atoms are arranged at the corners and center of each cube face of the cell.

Answer 6

Face-centered cubic Crystal Structure

Question 7

Atoms are assumed to touch along face diagonals (4 atoms in one unit cell)

Answer 7

Face-centered cubic Crystal Structure

Question 8

(example) ___ is a face-centered cubic or FCC lattice.

Answer 8

Diamond

Question 9

Each carbon atom joins four other carbon atoms in regular tetrahedrons ___

Answer 9

(triangular prisms).

Question 10

has atoms at each of the eight corners of a cube plus one atom in the center of the cube.

Answer 10

Body-Centered Cubic Crystal Structure (BCC)

Question 11

atoms touch each other along cube diagonals.

Answer 11

Body-Centered Cubic Crystal Structure (BCC)

Question 12

Crystalline substances can be described by the types of particles in them and the types of chemical bonding that take place between the particles.
There are four types of crystals:

Answer 12

(1) ionic,
(2) metallic,
(3) covalent network, and
(4) molecular.

Question 13

consists of alternating positively-charged cations and negatively-charged anions.

Answer 13

Ionic Crystals

Question 14

(Ionic Crystals) The ___ may either be monatomic or polyatomic.

Answer 14

ions

Question 15

Ionic crystals form from a combination of: group __?

Answer 15

Group 1 or 2 metals Group 16 or 17 nonmetals

Question 16

___ are hard and brittle and have high melting points.

Answer 16

Ionic crystals

Question 17

___ consist of metal cations surrounded by a “sea” of mobile valence electrons.

Answer 17

Metallic crystals

Question 18

Metallic crystals consist of metal cations surrounded by a “sea” of mobile valence electrons.
These electrons, also referred to as ___, do not belong to any one atom, but are capable of moving through the entire crystal. As a result, metals are good conductors of electricity.

Answer 18

delocalized electrons

Question 19

Common type of metallic crystals:

Answer 19

face-centered cubic (FCC), body-centered cubic (BCC), hexagonal closed-packed (HCP)

Question 20

___ consists of atoms at the lattice points of the crystal, with each atom being covalently bonded to its nearest neighbor atoms.

Answer 20

Covalent network crystal

Question 21

___ include diamond, quartz, many metalloids, and oxides of transition metals.

Answer 21

Network solids

Question 22

___ are hard and brittle, with extremely high melting and boiling points.

Answer 22

Network solids

Question 23

Network solids

Answer 23

Covalent network crystal

Question 24

___ typically consist of molecules at the lattice points of the crystal, held together by weak intermolecular forces.

Answer 24

Molecular crystals

Question 25

Molecular crystals, such as ice, have molecules held together by ___.

Answer 25

hydrogen bonds

Question 26

When one of the noble gases is cooled and solidified, the lattice points are ___

Answer 26

individual atoms

Question 27

the melting and boiling points of molecular crystals are much ___.

Answer 27

lower

Question 28

___ are substances that have weak intermolecular binding, such as dry ice (solidified carbon dioxide), solid forms of the noble gases (argon, krypton, and xenon)

Answer 28

Molecular crystals