Deck 18: The Solid State-A Particulate View

Question 1

Which element would be used to dope silicon to produce a p-type semiconductor?

A)boron (B)
B)carbon (C)
C)aluminum (Al)
D)phosphorus (P)
E)germanium (Ge)

Answer 1

aluminum (Al)

Question 2

Based on the approximate wavelength of light absorbed by the following materials,which one has the smallest band gap?

A)aluminum nitride, $\lambda$ = 206 nm
B)gallium nitride, $\lambda$ = 371 nm
C)indium nitride, $\lambda$ = 620 nm
D)boron-doped diamond, $\lambda$ = 675 nm
E)nitrogen-doped diamond, $\lambda$ = 425 nm

Answer 2

boron-doped diamond, $\lambda$ = 675 nm

Question 3

GaAs and AlGaAs₂ are examples of ________ semiconductors.

A)light-emitting diode (LED)
B)sound-emitting
C)np
D)non-
E)dual voltage

Answer 3

light-emitting diode (LED)

Question 4

Which of the following statements regarding band theory and solid-state bonding in lithium is NOT correct?

A)The 2s orbitals on lithium atoms overlap to form molecular orbitals.
B)Many lithium atoms are required for the overlap of atomic orbitals to form continuous bands of energies.
C)The metallic bonds holding lithium atoms together in the solid are fairly weak.
D)The valence band and the conduction band created by the overlap of atomic orbitals are both half full.
E)Lithium's conductivity is explained by the proximity of unoccupied orbitals in the conduction band to the occupied orbitals in the valence band.

Question 5

Metal solids are good conductors of electricity because ________

A)they are easily ionized.
B)their valence electrons are not localized.
C)they are easily reduced and oxidized.
D)they can be drawn into wires.
E)they are ductile.

Question 6

Band theory of bonding in solids ________

A)is an extension of molecular orbital theory.
B)describes bonds as rubber bands.
C)does not apply to any type of solid other than metals.
D)explains bond formation in metals,but not their physical properties.
E)All of the above are correct.

Question 7

When Ge is doped with Ga,it produces a(n)________-type semiconductor.

A)p
B)n
C)q
D)np
E)No semiconductor will be produced.

Question 8

What is the probable origin of cadmium's electrical conductivity when its electron configuration is [Kr]4d¹⁰5s²?

A)One electron on each atom is promoted to a 5p orbital when many cadmium atoms interact,and these electrons are free to move.
B)Empty 5p orbitals can be combined to form a conduction band overlaps the valence band,and electrons that move from the valence band to the conduction band are mobile.
C)Pairs of mobile electrons form when many cadmium atoms interact.
D)Cadmium has a very low ionization energy,which makes the valence electrons highly mobile.
E)4d orbitals mix with 5s orbitals,creating empty energy bands in which electrons can move.

Question 9

The molecular orbital description for metal bonding is different from that for diatomic molecules in that ________

A)there are no antibonding orbitals in the metal bonding description.
B)quantum theory no longer applies,as the orbitals are continuous.
C)the orbitals are so close in energy that they are referred to as bands.
D)the increased number of electrons results in each bond being stronger.
E)All of the above are true.

Question 10

When silicon is doped with gallium,electrical conduction increases because ________

A)gallium has fewer valence electrons than silicon so holes are created in the valence band of silicon.
B)gallium has more valence electrons than silicon so electrons are added to the conduction band of silicon.
C)gallium causes electrons to be transferred from the valence band of silicon to the conduction band of silicon.
D)gallium causes electrons to be transferred from the conduction band of silicon to the valence band of silicon.
E)gallium is a better conductor of electricity than silicon.

Question 11

Light-emitting diodes are semiconductors that emit light when a current is passed through them.What is the key factor that must be changed to change the wavelength of the emitted light in an LED?

A)the width of the valence band
B)the width of the conduction band
C)the width of the band gap
D)the magnitude of the current
E)the type of semiconductor (p vs.n)

Question 12

Which of the following can be used to increase the conductivity of any semimetal?
I.Adding an element with one additional valence electron
II.Adding an element with one fewer valence electron
III.Lowering the temperature

A)I only
B)II only
C)III only
D)I and II only
E)I,II and III

Question 13

Which element would be used to dope germanium to produce an n-type semiconductor?

A)Ga
B)Sn
C)Si
D)As
E)Cu

Question 14

Of C,Si,Ge,and Sn,which elements are semiconductors?

A)C and Si only
B)Si and Ge only
C)Ge and Sn only
D)None of these elements are semiconductors unless a dopant is added.
E)All of these elements are semiconductors.

Question 15

When Si is doped with P,it produces a(n)________-type semiconductor.

A)p
B)n
C)q
D)np
E)No semiconductor will be produced.

Question 16

The band structure of semiconductors differs from that of metal conductors in that ________

A)metal bands are relatively empty while semiconductor bands are nearly full.
B)metal bands are nearly full while semiconductor bands are relatively empty.
C)metal conduction bands are lower in energy than valence bands while semiconductor conduction bands are higher in energy than valence bands.
D)metal conduction bands are higher in energy than valence bands while semiconductor conduction bands are lower in energy than valence bands.
E)valence bands in metals are either partially empty or overlap with conduction bands while these bands in semiconductors are separated by a small gap.

Question 17

The bonding in solid-state metals can be described as ________

A)nonexistent.
B)a covalent network.
C)highly directional.
D)an electron sea.
E)ionic.

Question 18

Molecular orbital theory can be applied ________

A)only to two adjacent metal atoms.
B)only to a few metal atoms that are very close to each other.
C)to any number of metal atoms.
D)to nonmetals only-not to metals.
E)to nonmetals and ionic bonds only-not to metals.

Question 19

Which of the following is NOT a common characteristic of a metal?

A)shiny appearance
B)electrical conductivity
C)thermal conductivity
D)malleability
E)brittleness

Question 20

Electrical and thermal conductivity in metals ________

A)is explained by a dipolar coupling model.
B)is explained by band theory.
C)is explained by matrix isolation techniques.
D)is explained by temporary ionization.
E)is a function of the level of contamination by excess electrons.

Question 21

In the sodium chloride unit cell,the chloride ions form a cube in which each side is arranged as in the following figure.The circles represent the positions of the chloride ions on one square face of the cube.All the other faces are the same.What is the name of this unit cell?

A)cubic
B)chloride-centered cubic
C)face-centered cubic
D)x-face cubic
E)body-centered cubic

Question 22

How many nearest neighbor atoms are there around each atom in a simple cubic unit cell?

A)4
B)6
C)8
D)10
E)12

Question 23

How many nearest neighbor atoms are there around each atom in a face-centered cubic unit cell?

A)4
B)6
C)8
D)10
E)12

Question 24

Which of the following unit cells has the lowest packing efficiency?

A)simple cubic
B)face-centered cubic
C)body-centered cubic
D)both face-centered and body-centered cubic
E)Simple,face-centered,and body-centered cubic all have the same packing efficiency.

Question 25

At a historic Civil War battleground,a stack of cannonballs looked like the picture below on the far left.Removing the top cannonball resulted in the middle view,and removing the next layer resulted in the view on the right.What sort of packing was used in stacking the cannonballs?

A)cannonball closest-packed
B)hexagonal closest-packed
C)cubic closest-packed
D)random packed
E)body-centered closest-packed

Question 26

Iron exhibits polymorphism,the ability of a solid material to exist in more than one crystal form.At low to moderate temperatures,it adopts a bcc structure; at temperatures above 913 ^$\circ$ C,an fcc structure.Silicon carbide also has polymorphs,including the wurtzite form with abab packing and the sphalerite form with abcabc packing.Which of the following statements is NOT correct?

A)The bcc and fcc forms of iron probably have the same densities.
B)The packing efficiency of iron atoms in the bcc form is lower than that of the fcc form.
C)The two silicon carbide polymorphs probably have the same densities.
D)The packing efficiencies of the two silicon polymorphs are probably the same.
E)Both SiC polymorphs are based on hexagonal packing of atoms.

Question 27

Copper crystallizes in a face-centered cubic pattern.How many copper atoms are in each unit cell?

A)2
B)4
C)8
D)12
E)14

Question 28

The face-centered cubic structure is also known as ________

A)cubic closest-packed.
B)hexagonal closest-packed.
C)square closest-packed.
D)spherical closest-packed.
E)none of the above,as it is not a closest-packed pattern.

Question 29

Which of the following unit cells has the highest packing efficiency?

A)simple cubic
B)face-centered cubic
C)body-centered cubic
D)both face-centered and body-centered cubic
E)Simple,face-centered,and body-centered cubic all have the same packing efficiency.

Question 30

Which of the following have the highest packing efficiency?
I.Simple cubic
II.Body-centered cubic
III.Face-centered cubic
IV.Hexagonal closest packed

A)I and II
B)II and III
C)II and IV
D)I and III
E)III and IV

Question 31

In which of the following is/are the packing efficiency the lowest?
I.Tungsten,bcc
II.Titanium,hcp
III.Nickel,fcc
IV.Polonium,sc

A)I
B)II
C)III
D)IV
E)III and IV

Question 32

Polonium crystallizes in a simple cubic pattern.How many polonium atoms are in each unit cell?

A)1
B)2
C)3
D)4
E)5

Question 33

Which of the following statements is NOT true about a crystallographic unit cell?

A)It repeats throughout a crystalline structure in three dimensions.
B)It fills all the space in the crystalline lattice.
C)Its dimensions can be measured with X-rays.
D)It always has corners with 90 ^$\circ$ angles.
E)It represents the smallest repeating unit in the crystal.

Question 34

When a small amount of silver is added to zinc sulfide as an activator,the band gap of the resulting material is approximately 266 kJ/mol.If it were used as a light-emitting diode,what color of light would be emitted?

A)ultraviolet
B)infrared
C)red
D)yellow
E)blue

Question 35

The two types of closest-packed lattices are ________

A)cubic closest-packed and face-centered cubic.
B)cubic closest-packed and hexagonal closest-packed.
C)cubic closest-packed and random closest-packed.
D)cubic closest-packed and pyramidal closest-packed.
E)simple cubic and hexagonal closest-packed.

Question 36

A cubic closest-packed structure has hexagonally arranged layers of atoms in the series ________

A)ababab.
B)abcabcabc.
C)abcbabcbabcba.
D)abacabacaba.
E)aaaaaa.

Question 37

Iron crystallizes in a body-centered cubic pattern.How many iron atoms are in each unit cell?

A)1
B)2
C)4
D)8
E)9

Question 38

Which of the following statements regarding crystalline solids is NOT correct? If all are correct,choose E.

A)There is long-range,three-dimensional order in the arrangements of its constituent particles.
B)They are composed of regular repeating units called unit cells.
C)Atoms,molecules,or ions can form the crystalline lattice.
D)There is no empty space in a perfect crystalline solid.
E)All of the above are correct.

Question 39

How many nearest neighbor atoms are there around each atom in a body-centered cubic unit cell?

A)4
B)6
C)8
D)10
E)12

Question 40

Pure solid metals ________

A)do not crystallize.
B)are amorphous.
C)often crystallize in closest-packed structures.
D)often crystallize in very complex unit cells.
E)are like liquids with the nuclei flowing through a sea of electrons.

Question 41

Which of the following refers to an alloy in which the composition of the elements is variable and one element must have a much smaller radius than the other?

A)intermetallic
B)interstitial
C)stoichiometric
D)substitutional
E)inhomogeneous

Question 42

Aluminum (Al)crystallizes as a face-centered unit cell with an edge length of 404 pm.What is the atomic radius of aluminum?

A)143 pm
B)202 pm
C)286 pm
D)175 pm
E)808 pm

Question 43

Which of the following refers to an alloy in which the composition is variable and the elements have comparable radii?

A)intermetallic
B)interstitial
C)stoichiometric
D)substitutional
E)homogeneous

Question 44

Which of the following is NOT an example of an ore?

A)hematite (Fe₂O₃)
B)chalcocite (Cu₂S)
C)argentite (Ag₂S)
D)chalcopyrite (CuFeS₂)
E)quartz (SiO₂)

Question 45

If a face-centered cubic unit cell has a volume of 1.45 $\times$ 10⁸ pm³ and the atoms at the corners touch the atom on the face,what must be the atom's radius?

A)186 pm
B)388 pm
C)4240 pm
D)125 pm
E)1050 pm

Question 46

The $\alpha$ form of polonium (Po)crystallizes as a simple cubic unit cell with an edge length of 335 pm.What is the atomic radius of polonium?

A)84 pm
B)168 pm
C)335 pm
D)175 pm
E)808 pm

Question 47

Gold (Au)has a face-centered cubic structure with a unit cell edge length of 407.8 pm.What is the calculated value of the density of gold based on this information?

A)15.78 g/cm³
B)19.30 g/cm³
C)9.648 g/cm³
D)4.824 g/cm³
E)11.60 g/cm³

Question 48

If a body-centered cubic unit cell has a volume of 1.45 $\times$ 10⁸ pm³,what must be the dimension of the cube's edge?

A)1.13 $\times$ 10⁸ pm
B)1.10 $\times$ 10² pm
C)1.20 $\times$ 10⁴ pm
D)525 pm
E)367 pm

Question 49

The $\alpha$ form of polonium (Po)has a density of 9.196 g/cm³ and crystallizes in a simple cubic structure.What is the atomic radius of polonium?

A)119 pm
B)168 pm
C)266 pm
D)335 pm
E)419 pm

Question 50

Iron (Fe)has a density of 7.87 g/cm³ and crystallizes in a body-centered cubic structure.What is the atomic radius of iron?

A)99.0 pm
B)114 pm
C)124 pm
D)143 pm
E)255 pm

Question 51

Which of the following refers to an alloy in which the composition of the elements is constant?

A)intermetallic
B)interstitial
C)stoichiometric
D)substitutional
E)homogeneous

Question 52

Aluminum (Al)has a density of 2.70 g/cm³ and crystallizes in a face-centered cubic structure.What is the unit-cell edge length?

A)2.47 $\times$ 10^-3 pm
B)40.0 pm
C)405 pm
D)321 pm
E)255 pm

Question 53

Gold has a face-centered cubic structure with a unit cell edge length of 407.8 pm.What is the density of each individual gold atom?

A)21.44 g/cm³
B)26.06 g/cm³
C)13.10 g/cm³
D)6.550 g/cm³
E)19.28 g/cm³

Question 54

If the unit cell of copper has an edge length of approximately 362 pm and the radius of a copper atom is approximately 128 pm,what is copper's probable crystal structure?

A)simple cubic
B)side-centered cubic
C)body-centered cubic
D)face-centered cubic
E)more information is required

Question 55

If tungsten (W)adopts a bcc structure with a unit cell edge length of 321 pm,what is the length of the body diagonal across the unit cell (from opposite corners on opposite faces)?

A)731 pm
B)454 pm
C)139 pm
D)556 pm
E)185 pm

Question 56

Iron (Fe)crystallizes as a body-centered unit cell with an edge length of 287 pm.What is the atomic radius of iron?

A)99.0 pm
B)114 pm
C)124 pm
D)143 pm
E)256 pm

Question 57

An unknown metal with an fcc structure has a density of 10.5 g/cm³,and the edge length of the unit cell is 409 pm.What is the probable identity of the metal?

A)silver
B)manganese
C)aluminum
D)samarium
E)more information is required

Question 58

Which of the following can be varied to change the physical properties of an alloy?
I.The elements used
II.The proportions used
III.The type of hole each element occupies

A)I only
B)II only
C)III only
D)I and II only
E)I,II,and III

Question 59

Sodium (22.99 g/mol)and potassium (39.10 g/mol)both adopt a bcc structure.The radius of a potassium atom is approximately 1.23 times that of a sodium atom,and potassium's bulk density is about 1.98 g/cm³.What is the approximate density of sodium?

A)1.09 g/cm³
B)1.61 g/cm³
C)1.70 g/cm³
D)2.17 g/cm³
E)2.44 g/cm³

Question 60

Which unit cell contains the most atoms?

A)fcc
B)bcc
C)cubic
D)both fcc and bcc
E)None of the above,as fcc,bcc,and cubic contain the same number of atoms.

Question 61

Solder is a fusible metal alloy used to join together metal wires or work pieces.Old-style solder was often 60% tin (r = 140 pm)and 40% lead (r = 154 pm).Heating the solder caused it to melt; upon cooling,small sites would develop that were richer in Pb,which has a higher melting point than Sn.Cooled solder is best classified as ________

A)a homogeneous alloy.
B)a heterogeneous alloy.
C)an interstitial alloy.
D)a colloidal alloy.
E)an intermetallic compound.

Question 62

In comparing the density of bronze composed of 20% tin (r = 140 pm,7.37 g/cm³)to the density of pure copper (r = 128 pm,8.92 g/cm³),________

A)the density of the bronze is lower.
B)the density of the bronze is higher.
C)the density of the bronze is the same.
D)the density of the bronze depends on whether the tin or the copper occupies holes.
E)It cannot be determined as only the 1:1 intermetallic compound of tin and copper has ever been observed.

Question 63

Bronze that is composed of 10% tin (r = 140 pm)and 90% copper (r = 128 pm)is ________

A)a substitutional alloy.
B)an interstitial alloy.
C)a doped semiconductor.
D)a colloidal alloy.
E)an intermetallic compound.

Question 64

Mangalloy is a nonmagnetic steel with extreme anti-wear properties.It contains approximately 0.8-1.25% carbon (r = 77 pm)and 11-15% manganese (r = 127 pm),along with iron (r = 126 pm).Mangalloy is ________

A)a substitutional alloy.
B)an interstitial alloy.
C)both an interstitial and substitutional alloy.
D)a colloidal alloy.
E)an intermetallic compound.

Question 65

Terne,originally an alloy of lead (r = 154 pm,fcc)and tin (r = 140 pm),appears to contain approximately 7 tin atoms for every 16 lead atoms.Which of the following statements regarding the alloy is correct?

A)It is probably an interstitial alloy with tin occupying some of the octahedral holes.
B)It is probably an interstitial alloy with tin occupying some of the tetrahedral holes.
C)It is probably an interstitial alloy with tin occupying some of the cubic holes.
D)It is probably a substitutional alloy.
E)It is approximately 70% Pb and 30% Sn.

Question 66

Aluminum is resistant to corrosion because of ________

A)its positive oxidation potential.
B)its low density.
C)the formation of a protective surface film of aluminum oxide.
D)the formation of a protective surface film of aluminum nitride.
E)its lack of reactivity toward oxygen.

Question 67

In a two-component alloy,the more abundant metal can be thought of as the solvent while the less abundant metal can be thought of as the solute.Which of the following is an explanation of why an alloy is often harder than either of the pure elements?
I.In a homogenous substitutional alloy,the solute atoms distort the crystal structure a bit,making it hard for atoms to slip past one another.
II.In a heterogeneous alloy,small regions rich in the solute atom can disrupt the crystal lattice,making it hard for atoms to slip past one another.
III.When solute atoms occupy interstices,they can prevent the atoms in the crystal structure from slipping past one another.

A)only I
B)only II
C)only III
D)I or II
E)I,II,or III

Question 68

Structural forms of an element in which the atoms are bonded together in a different manner are called ________

A)polymers.
B)allotropes.
C)isotopes.
D)isoforms.
E)polymorphs.

Question 69

In addition to carbon and iron,stainless steel contains ________

A)teflon and polyethylene.
B)gold and silver.
C)copper and nickel.
D)chromium and nickel.
E)platinum.

Question 70

Boron (r = 88 pm)is sometimes added to steel alloys as a hardening agent.Suppose one alloy contains approximately one B atom for every 1920 Fe atoms (r = 126 pm).Which of the following statements regarding the boron in alloy is correct?

A)Boron probably occupies a small fraction the octahedral holes in the iron crystal lattice.
B)Boron probably occupies a small fraction the tetrahedral holes in the iron crystal lattice.
C)Boron probably occupies a small fraction the cubic holes in the iron crystal lattice.
D)Boron probably replaces a small fraction of the iron atoms in the crystal lattice.
E)The alloy is approximately 0.05% boron by mass.

Question 71

Which of the following is NOT associated with the production of iron from iron ore in blast furnaces?

A)Iron ore,coke,and limestone are used.
B)Solid by-products collect on top of molten iron,which is removed from the bottom of the reaction vessel.
C)Molten iron crystallizes at its melting point of 1538 ^$\circ$ C in a bcc structure but then undergoes a phase transition at around 1390 ^$\circ$ C to a fcc structure.
D)Limestone (CaCO₃)decomposes to form lime (CaO),which can react with silica impurities (SiO₂)in the iron ore.
E)The carbon content is reduced by heating the impure molten iron in a second furnace to temperatures above 1600 ^$\circ$ C.

Question 72

The higher the carbon content in steel,________

A)the stronger and more malleable it is.
B)the stronger and more brittle it is.
C)the weaker and more malleable it is.
D)the weaker and more brittle it is.
E)Any of these,depending on the formula of the interstitial compound.

Question 73

How many carbons are bonded to each carbon in graphite?

A)1
B)2
C)3
D)4
E)some have 2 and some have 3

Question 74

Aluminum alloys are more desirable than steel in some applications because of their relatively ________

A)low density.
B)low cost.
C)high luster.
D)high warmth to touch.
E)high conductivity.

Question 75

Nickel aluminide,Ni₃Al,is sometimes used as a strengthening constituent in high-temperature nickel-base superalloys.It is approximately 13.3% aluminum (r = 143 pm)and 86.7% nickel (r = 124 pm).Ni₃Al is best classified as ________

A)a substitutional alloy.
B)an interstitial alloy.
C)both an interstitial and substitutional alloy.
D)a colloidal alloy.
E)an intermetallic compound.

Question 76

In a two-component alloy the more abundant metal can be thought of as the solvent while the less abundant metal can be thought of as the solute.Which of the following would NOT change the orientation of atoms in the solvent's unit cell? I)A solute with the same atomic radius as the solvent
II)A solute that was sufficiently small to fit into holes in the solvent's unit cell
III)A solvent that was sufficiently small to fit into holes in the solute's unit cell

A)only I
B)only II
C)only III
D)I or II
E)I,II,or III

Question 77

The most common allotrope of carbon is ________

A)coal.
B)graphite.
C)soot.
D)diamond.
E)carbon steel.

Question 78

Suppose approximately one-third of the octahedral holes in the fcc lattice of iron (r = 126 pm)is occupied by a carbon atom (r = 77 pm).Which of the following is its probable composition?

A)FeC.
B)FeC₃.
C)Fe₃C.
D)Fe₃C₃.
E)Carbon cannot occupy the octahedral holes in the iron crystal lattice.

Question 79

Stainless steel is less susceptible to rusting than iron because ________

A)it is coated with plastic.
B)the metals other than iron in the alloy are oxidized more easily,forming protective oxides.
C)the carbon within the alloy polymerizes to form a protective film.
D)the silicon within the alloy oxidizes to form a protective silicate layer.
E)the intermetallic compound formed is less reactive.

Question 80

An approximately spherical allotrope of carbon containing 60 or 70 atoms is ________

A)spherohexadecalene and spheroheptadecalene.
B)spheralene-60 and spheralene-70.
C)fullerene.
D)graphitolene.
E)soccerene.