Chang: Chemistry 7th Edition - Chapter 11
CH116 General Chemistry II
INTERMOLECULAR FORCES
Inter-molecular Forces
Have studied INTRAmolecular forces—the forces holding atoms together to form molecules.
Now turn to forces between molecules — INTERmolecular forces.
Forces between molecules, between ions, or between molecules and ions.
Table 13.1 Summary of Intermolecular Forces
Ions
Dipoles
Induced Dipoles
(Overhead & book p 585)
Covalent bond energies 100-400 kJ/mol
Attractive forces between ions 700-100 kJ/mol
Intermolecular attractions less than 15% of bond energies
Intermolecular Forces
Ion-Ion Forces
Na+ — Cl- in salt.
These are the strongest forces.
Lead to solids with high melting temperatures.
NaCl, mp = 800 oC
MgO, mp = 2800 oC
Intermolecular Attractions
Coulomb’s Law
Force ~ (n+)(n-)/d2
Distance - twice the distance = 1/4 the force
Charge on the Ion
Magnitude of the dipole
Composition - Solids and Liquids are closer so composition has greater role in attractive forces
Attraction Between Ions and Permanent Dipoles
Water is highly polar and can interact with positive ions to give hydrated ions in water.
Attraction Between Ions and Permanent Dipoles
Water is highly polar and can interact with positive ions to give hydrated ions in water.
Dissolving Ionic Solids
Attraction Between Ions and Permanent Dipoles
Many metal ions are hydrated.
It is the reason metal salts dissolve in water.
Attraction Between Ions and Permanent Dipoles
Attraction between ions and dipole depends on ion charge and ion-dipole distance.
Measured by
DHhydration for Mn+ + H2O --> [M(H2O)x]n+
Solvation (aka hydration)
Attraction Between Ions and Permanent Dipoles
Attraction between ions and dipole depends on ion charge and ion-dipole distance.
Measured by DH for Mn+ + H2O --> [M(H2O)x]n+
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Consider the following
Explain why the enthalpy of hydration of sodium ions (-405 kJ/mol) is somewhat more negative than
cesium ions (-263 kJ/mol) whereas that of magnesium ions is much more negative than either at -1922
kJ/mol
Which should have the more negative enthalpy of hydration: fluorine or chlorine?
Fluorine or bromine? Rubidium or Strontium? Sodium or chloride?
Explain the following
Dipole-Dipole Forces
Such forces bind molecules having permanent dipoles to one another.
Dipole-Dipole Forces
Such forces bind molecules having permanent dipoles to one another.
Dipole-Dipole Forces
Influence of dipole-dipole forces is seen in the boiling points of simple molecules.
Compd
N2
CO
Br2
ICl
Mol. Wt.
28
28
160
162
Boil Point
-196 oC
-192 oC
59 oC
97 oC
Dipole-Dipole Forces
Influence of dipole-dipole forces is seen in the boiling points of simple molecules.
Hydrogen Bonding
A special form of dipole-dipole attraction, which enhances dipole-dipole attractions.
Hydrogen Bonding
A special form of dipole-dipole attraction, which enhances dipole-dipole attractions.
H-bonding is strongest when X and Y are
N, O, or F
Query: How do you recognize when hydrogen bonding will occur between molecules?
H-Bonding Between Methanol and Water
H-Bonding Between Two Methanol Molecules
H-Bonding Between Ammonia and Water
Strength of Dipole depends on Factors:
electronegativity difference - the greater the difference, the more polarized the dipole, the stronger the
attractions, the higher the melting point and boiling point, the lower the vapor pressure
atomic size - small atomic size concentrates charge on ions/dipole increasing the strength of the dipole,
increasing mp and bp, lowering vapor pressure
Query: How can relative BP be predicted for an analogous series of compounds?
Hydrogen Bonding
Boiling Points
Explain the observed trends in boiling points for representative hydrogen compounds
Why are boiling points important predictors?
Overhead: Temperature vs. Period
Query: Why is the observed boiling point of dihydrogen selenide higher than that of dihydrogen sulfide but
lower than that of dihydrogen oxide?
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Indicators of Intermolecular Force
Enthalpy of vaporization
Boiling point - review table 13.2
(overhead - types of IA - BP/MW/#e-)
Solublility “like dissolves like”
Hydrogen Bonding in H2O
H-bonding is especially strong in water because
the O—H bond is very polar
there are 2 lone pairs on the O atom
Accounts for many of water’s unique properties.
Hydrogen Bonding in H2O
H-bonding in H2O ----> open lattice like structure of ice.
Ice density is less than that of liquid, and solid floats on water.
Hydrogen Bonding in H2O
H-bonding in H2O ----> open lattice like structure of ice.
Ice density is less than that of liquid, and solid floats on water.
Ice: 13m07an2
Hydrogen Bonding in H2O
H bonds ---> abnormally high specific heat capacity of water (4.184 g/K•mol).
This is the reason water is used to put out fires, it is the reason lakes/oceans control climate, and is the
reason thunderstorms release huge energy.
Hydrogen Bonding
H bonds ---> abnormally high boiling point of water.
FORCES INVOLVING INDUCED DIPOLES
How can non-polar molecules such as Br2, I2, and N2 condense to form liquids and solids?
Consider I2 dissolving in alcohol, CH3CH2OH.
FORCES INVOLVING INDUCED DIPOLES
How can non-polar molecules such as Br2, I2, and N2 condense to form liquids and solids?
Consider I2 dissolving in alcohol, CH3CH2OH.
FORCES INVOLVING INDUCED DIPOLES
Water induces a dipole in nonpolar O2 molecules, and so O2 can dissolve in water.
[O2] = 8 mg/L at 25 C
Solubility of Gases
FORCES INVOLVING INDUCED DIPOLES
Formation of a dipole in two nonpolar I2 molecules.
FORCES INVOLVING INDUCED DIPOLES
The induced forces between I2 molecules are very weak, so solid I2 sublimes (goes from a solid to
gaseous molecules).
FORCES INVOLVING INDUCED DIPOLES
The size of the dipole depends on the tendency to be distorted.
Higher molecular weight ---> larger induced dipoles.
Molecule
Boiling Point (oC)
CH4 (methane) - 161.5
C2H6 (ethane)
- 88.6
C3H8 (propane) - 42.1
C4H10 (butane) - 0.5
Factors affecting strength
Boiling Points of Hydrocarbons
Note linear relation between bp and molar mass.
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Problem Solving
Why are the intermolecular attractive forces stronger in liquids and solids than they are in gases?
Which is expected to have a higher boiling point, C8H18 or C4H8?
What kinds of intermolecular attractive forces (dipole-dipole, London, hydrogen bonding) are present in
the following substances? HF, CS2, PCl3, SF6, SO2
Problem Solving
What intermolecular forces are involved in the following
liquid methane
mixture of water and methanol
solution of lithium chloride in water
nitrogen gas dissolved in water
Overheads: Summary of Intermolecular forces & Flow Chart of Intermolecular forces
Factors affecting properties
Liquids
In a liquid
•
molecules are in constant motion
•
there are appreciable intermolec. forces
•
molecules close together
•
Liquids are almost incompressible
•
Liquids do not fill the container
Liquids
The two key properties we need to describe are EVAPORATION and its opposite—CONDENSATION
Liquids
The two key properties we need to describe are EVAPORATION and its opposite—CONDENSATION
Liquids
To evaporate, molecules must have sufficient energy to break IM forces.
Evaporation
Problem Solving
Why does evaporation lower the temperature of a liquid?
Why does increasing a liquids temperature increase the rate of evaporation?
Would increasing the volume of liquid in a container change the equilibrium vapor pressure?
Liquids
Distribution of molecular energies in a liquid.
KE is propor-tional to T.
Liquids
At higher T a much larger number of molecules has high enough energy to break IM forces and move
from liquid to vapor state.
High E molecules carry away E. You cool down when sweating or after swimming.
Applications:
How much heat is needed to evaporate 1.00 L of water at 100 ºC
Review Table 13.4 for needed physical constants
(H2O MW=18.0 g/mol, ∆Hvap=24.9 kJ/mol,
BP at 760 mmHg= 100.00 ºC)
Applications:
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The molar enthalpy of vaporization of methanol, CH3OH is 35.2 kJ/mol at 64.6 ºC.
How much energy is required to evaporate 1.00 kg at its boiling point of 64.6 ºC?
Liquids
Section 13.3
When molecules of liquid are in the vapor state, they exert a VAPOR PRESSURE
EQUILIBRIUM VAPOR PRESSURE is the pressure exerted by a vapor over a liquid in a closed container
when the rate of evaporation = the rate of condensation.
Vapor Pressure
FIGURE 13.19 (Overhead)
shows VP as a function of T.
1. The curves show all conditions of P and T where LIQUID and VAPOR are in EQUILIBRIUM.
2. The VP rises with T.
3. When VP = external P, the liquid boils.
This means that BP’s of liquids change with altitude.
Vapor Pressure
Problem Solving
Why does increasing a liquids temperature increase the rate of evaporation?
Would increasing the volume of liquid in a container change the equilibrium vapor pressure?
Would increasing the size of the container change the equilibrium vapor pressure?
Would increasing the temperature in the container change the equilibrium vapor pressure?
Why does moisture condense on the outside of a cool glass in summertime?
Boiling Liquids
section 11.7, Figure 11.20
Liquid boils when its vapor pressure equals atmospheric pressure.
Boiling Point at Lower Pressure
When pressure is lowered, the vapor pressure can equal the external pressure at a lower temperature.
Consequences of Vapor Pressure Changes
When can cools, vp of water drops. Pressure in the can is less than that of atmosphere, so can is
crushed.
Problem Solving
Mt Kilimanjaro in Tanzania is the tallest peak in Africa at 19,340 ft. The normal barometric pressure at the
peak is about 345 torr. What is the expected boiling point at this elevation? Refer to overhead p92 or
chart in textbook (11.17)
How does a pressure cooker work?
The radiator cap of an automobile engine is designed to maintain a pressure of about 15 lb/in2 above
normal atmospheric pressure. What is the design pressure of the cap? How does this reduce the risk of
having the engine boil over?
Liquids
FIGURE 11.17 shows VP as a function of T.
4. If external P = 760 mm Hg, T of boiling is the NORMAL BOILING POINT
5. VP of a given molecule at a given T depends on IM forces. Here the VP’s are in the order
Vapor Pressure
Problem Solving
Ethanol, CH3CH2OH, has a vapor pressure of 59 mm Hg at 25 ºC. What quantity of heat energy is
required to evaporate 125 mL of the alcohol at 25 ºC? Then enthalpy of vaporization of the alcohol at 25
ºC is 42.43 kJ/mol. The density of the liquid is 0.7948 g/mL.
Liquids
FIGURE 11.17 shows VP as a function of T.
4. If external P = 760 mm Hg, T of boiling is the NORMAL BOILING POINT
5. VP of a given molecule at a given T depends on IM forces. Here the VP’s are in the order
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Liquids
HEAT OF VAPORIZATION is the heat req’d (at constant P) to vaporize the liquid.
LIQ + heat ---> VAP
Compd.
DH
Hvap (kJ/mol) IM Force
40.7 (100 oC) H-bonds
H2O
SO2
26.8 (-47 oC) dipole
Xe
12.6 (-107 oC) induced dipole
Problem Solving
The molar heat of vaporization of water at 25°C is +43.9 kJ/mol. How many kilojoules of heat would be
required to vaporize 125 mL of water?
Would the heat of condensation be exothermic or endothermic
Rank the following compounds in terms of increasing values for ∆Hvaporization:
HF, CH4, CF4, HCl
Review
Suppose that 45.0 g of water at 85°C is added to 105.0 g of ice at 0°C. The molar heat of fusion of water
is 6.01 kJ/mol and the specific heat of water is 4.18 J/g°C. Based on this: a) what will be the final
temperature of the mixture and b) how many grams of ice will melt?
Properties of Liquids
Critical Temperature and Pressure (overhead)
Surface Tension & Capillary Action
Viscosity
Liquids
Molecules at surface behave differently than those in the interior.
Liquids
Molecules at surface behave differently than those in the interior.
Liquids
Molecules at surface behave differently than those in the interior.
Molecules at surface experience net INWARD force of attraction.
Liquids
Molecules at surface behave differently than those in the interior.
Molecules at surface experience net INWARD force of attraction.
This leads to SURFACE TENSION — the energy req’d to break the surface.
Surface Tension
SURFACE TENSION also leads to spherical liquid droplets.
Liquids
Intermolec. forces also lead to CAPILLARY action and to the existence of a concave meniscus for a water
column.
Capillary Action
Movement of water up a piece of paper depends on H-bonds between H2O and the OH groups of the
cellulose in the paper.
Problem Solving
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You place 2.00 L of water in your dormitory room, which has a volume of 4.33x104 L. You seal the room
and wait for the water to evaporate. Will all of the water evaporate at 25 ºC? The density of water at this
temperature is 0.997 g/mL and the equilibrium vapor pressure at this temperature is 23.8 mm Hg.
Clausius-Clapeyron Equation
Instead of plotting VP vs. T they plotted the natural logrithm of vapor pressure against the reciprocal of
the Kelvin Temperature
Clausius-Clapeyron
Problem Solving
Hexane, C6H14, a component of paint thinners, has ∆Hvap = 30.1 kJ/mol. At room temperature (25°C), the
vapor pressure of hexane is 148 torr. What is the vapor pressure of hexane at 50°C.
Problem Solving
Ethyl acetate, a solvent for certain plastics, has a vapor presure of 72.8 torr at 20 °C and a vapor
pressure of 186.2 torr at 40 °C. Estimate the value of the enthalpy of vaporization in kilojoules per mole.
Dynamic equilibrium
Problem Solving
Given the reaction system below at equilibrium in a closed vessel at 500 ºC and 350 atmospheres in
pressure, how would the equilibrium be influenced by the following changes:
N2 (g) + 3 H2 (g) <=> 2 NH3 (g) + 92 kJ
increasing temperature
increasing pressure with helium gas
removing ammonia from the flask
adding hydrogen to the flask
increasing the volume of the vessel
adding some catalyst
decreasing the temperature of the vessel
Metallic and Ionic Solids
Section 13.4
Types of Solids
Table 13.6 page 610-611
TYPE EXAMPLE
FORCE
Ionic NaCl, CaF2, ZnS
Ion-ion
Metallic Na, Fe
Metallic
Molecular
Ice, I2
Dipole
Ind. dipole
Network
Diamond
Extended
Graphite
covalent
Network Solids
Network Solids
A comparison of diamond (pure carbon) with silicon.
Properties of Solids
1. Molecules, atoms or ions locked into a
CRYSTAL LATTICE
2. Particles are CLOSE together
3. STRONG IM forces
4. Highly ordered, rigid,
incompressible
Crystal Lattices
Regular 3-D arrangements of equivalent LATTICE POINTS in space.
The lattice points define UNIT CELLS, the smallest repeating internal unit that has the symmetry
characteristic of the solid.
There are 7 basic crystal systems, but we are only concerned with CUBIC.
Cubic Unit Cells
Cubic Unit Cells
Figure 13.28
Metals have unit cells that are
•
simple cubic (SC)
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•
•
body centered cubic (BCC)
face centered cubic (FCC)
Simple cubic unit cell.
Note that each atom is at a corner of a unit cell and is shared among 8 unit cells.
Body-Centered Cubic Unit Cell
Face Centered Cubic Unit Cell
Atom at each cube corner plus atom in each cube face.
Crystal Lattices—Packing of Atoms or Ions
Assume atoms are hard spheres and that crystals are built by PACKING of these spheres as efficiently as
possible.
FCC is more efficient than either BC or SC.
Packing of C60 molecules. They are arranged at the lattice points of a FCC lattice.
Finding the Lattice Type
To find out if a metal is SC, BCC or FCC, use the known radius and density of an atom to calc. no. of
atoms per unit cell.
PROBLEM Al has density = 2.699 g/cm3 and Al radius = 143 pm. Verify that Al is FCC.
SOLUTION
1.
Calc. unit cell volume
Finding the Lattice Type
PROBLEM Al has density = 2.699 g/cm3 and Al radius = 143 pm. Verify that Al is FCC.
SOLUTION
1. Calc. unit cell volume
V = (cell edge)3
Edge distance comes from face diagonal.
Diagonal distance = Ö2
2 • edge
Finding the Lattice Type
PROBLEM Al has density = 2.699 g/cm3 and Al radius = 143 pm. Verify that Al is FCC.
SOLUTION
V = (cell edge)3 and face diagonal = Ö2
2 • edge
Finding the Lattice Type
PROBLEM Al has density = 2.699 g/cm3 and Al radius = 143 pm.
SOLUTION
Here diagonal = 4 • radius of Al = 572 pm
Therefore, edge = 572 pm / Ö2
2 = 404 pm
In centimeters, edge = 4.04 x 10-8 cm
So, V of unit cell = (4.04 x 10-8 cm)3
V = 6.62 x 10-23 cm3
Finding the Lattice Type
PROBLEM Al has density = 2.699 g/cm3 and Al radius = 143 pm.
SOLUTION
2.
Use V and density to calc. mass of unit cell from DENS =
Mass = density • volume
= (6.62 x 10-23 cm3)(2.699 g/cm3)
= 1.79 x 10-22 g/unit cell
Finding the Lattice Type
PROBLEM Al has density = 2.699 g/cm3 and Al radius = 143 pm.
SOLUTION
3. Calculate number of Al per unit cell from mass of unit cell.
Verify that Al is FCC.
Verify that Al is FCC.
MASS / VOL
Verify that Al is FCC.
Finding the Lattice Type
PROBLEM Al has density = 2.699 g/cm3 and Al radius = 143 pm. Verify that Al is FCC.
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SOLUTION
3. Calculate number of Al per unit cell from mass of unit cell.
1 atom = 4.480 x 10-23 g, so
Finding the Lattice Type
PROBLEM Al has density = 2.699 g/cm3 and Al radius = 143 pm. Verify that Al is FCC.
SOLUTION
3. Calculate number of Al per unit cell from mass of unit cell.
1 atom = 4.480 x 10-23 g, so
Number of Atoms per Unit Cell
How can there be 4 atoms in a unit cell?
1. Each corner Al is 1/8 inside the unit cell.
8 corners (1/8 Al per corner) = 1 net Al
2. Each face Al is 1/2 inside the cell
6 faces (1/2 per face) = 3 net Al’s
Number of Atoms per Unit Cell
Unit Cell Type
Net Number Atoms
FCC
4
SC
1
BCC
2
Example 13.6
Aluminum has a density of 2.699 g/cm3, and the atoms are packed into a face-centered cubic unit cell.
Use this information to find the radius of an aluminum atom
Example 13.7
Iron has a density of 7.8740 g/cm3, and the radius of an iron atom is 126 pm.
Verify that the structure of the solid is a body-centered cube
Enthalpy of Fusion
Properties of Solids
At the Melting point the crystal lattice collapses
Non-polar substances generally have low melting points that increase with MW & size
Ionic substances have higher melting points and enthalpies of fusion
Increasing anion/cation size decreases lattice energy and thus mp and fusion
sublimation, like fusion and evaporation is an endothermic process
PHASE Diagrams
Section 13.7
See the phase diagram for water, Figure 13.37.
Lines connect all conditions of T and P where EQUILIBRIUM exists between the phases on either side of
the line.
(At equilibrium particles move from liquid to gas as fast as they move from gas to liquid, for example.)
Phase Diagram for Water
Important Points for Water
T(°C
C)
P(mmHg)
Normal boil point
100
760
Normal freeze point
0
760
Triple point
0.0098 4.58
TRANSITIONS
BETWEEN PHASES
As P and T increase, you finally reach the CRITICAL T and P
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TRANSITIONS
BETWEEN PHASES
As P and T increase, you finally reach the CRITICAL T and P
TRANSITIONS
BETWEEN PHASES
As P and T increase, you finally reach the CRITICAL T and P
Critical T and P
COMPD
Tc(oC)
Pc(atm)
H2O
374
218
C O2
31
73
- 82
46
CH4
Freon-12
112
41
(CCl2F2)
Notice that Tc and Pc depend on intermolecular forces.
Solid-Liquid Equilibria
In any system, if you increase P the DENSITY will go up.
Therefore — as P goes up, equilibrium favors phase with the larger density (or SMALLER volume/gram).
Liquid H2O
Solid H2O
Density
1 g/cm3
0.917 g/cm3
cm3/gram
1
1.09
Solid-Liquid Equilibria
In any system, if you increase P the DENSITY will go up.
Therefore — as P goes up, equilibrium favors phase with the larger density (or SMALLER volume/gram).
Liquid H2O
Solid H2O
Density
1 g/cm3
0.917 g/cm3
cm3/gram
1
1.09
Solid-Liquid Equilbria
Raising the pressure at constant T causes water to melt.
The NEGATIVE SLOPE of the S/L line is unique to H2O. Almost everything else has positive slope.
Solid-Liquid Equilbria
The behavior of water under pressure is an example of
LE CHATELIER’S PRINCIPLE
At Solid/Liquid equilibrium, raising P squeezes the solid.
It responds by going to phase with greater density, i.e., the liquid phase.
Solid-Vapor Equilibrium
At P < 4.58 mmHg and T < 0.0098 ° C
solid H2O can go directly to vapor. This process is called SUBLIMATION
This is how a frost-free refrigerator works.
.Why are the intermolecular attractive forces stronger in liquids and solids than they are in gases?
.Which is expected to have a higher boiling point, C8H18 or C4H8?
.What kinds of intermolecular attractive forces (dipole-dipole, London, hydrogen bonding) are present in
the following substances? HF, CS2, PCl3, SF6, SO2
.The formula for glycerol is H2C(OH)HC(OH)H2C(OH). Would you expect this liquid to wet glass
surfaces?
.Why does evaporation lower the temperature of a liquid?
.Why does increasing a liquids temperature increase the rate of evaporation?
.Would increasing the volume of liquid in a container change the equilibrium vapor pressure?
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Dr. Myton, CH116
.Would increasing the size of the container change the equilibrium vapor pressure?
.Would increasing the temperature in the container change the equilibrium vapor pressure?
.Why does moisture condense on the outside of a cool glass in summertime?
.Mt Kilimanjaro in Tanzania is the tallest peak in Africa at 19,340 ft. The normal barometric pressure at
the peak is about 345 torr. What is the expected boiling point at this elevation? Refer to overhead p92 or
chart in textbook (11.17)
.How does a pressure cooker work?
.The radiator cap of an automobile engine is designed to maintain a pressure of about 15 lb/in2 above
normal atmospheric pressure. What is the design pressure of the cap? How does this reduce the risk of
having the engine boil over?
.Butane, with a boiling point of 31°F, is easily observed as a liquid in typical butane lighters. Why isn’t the
butane boiling inside the lighter?
.The molar heat of vaporization of water at 25°C is +43.9 kJ/mol. How many kilojoules of heat would be
required to vaporize 125 mL of water?
.Would the heat of condensation be exothermic or endothermic?
.Suppose that 45.0 g of water at 85°C is added to 105.0 g of ice at 0°C. The molar heat of fusion of water
is 6.01 kJ/mol and the specific heat of water is 4.18 J/g°C. Based on this: a) what will be the final
temperature of the mixture and b) how many grams of ice will melt?
.Ethyl acetate, a solvent for certain plastics, has a vapor pressure of 72.8 torr at 20°C and a vapor
pressure of 186.2 torr at 40°C. Estimate the value of ∆Hvap for this solvent in kJ/mol.
.What is the vapor pressure of the same solvent at 60°C?
.According to the phase diagram for carbon dioxide, what phase(s) should exist at:
a) -60°C and 6 atm
b) -60°C and 2 atm
c) -40°C and 10 atm
d) -57°C and 5.2 atm
.How can the phase diagram indicate that solid carbon dioxide is more dense than liquid?
.Rank the following compounds in terms of increasing values for ∆Hvaporization:
HF, CH4, CF4, HCl
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.Tin(IV) chloride has soft crystals with a melting point of –30.2°C, the liquid is nonconducting. What type
of crystal is formed?
.Elemental boron is a semiconductor, it is very hard and has a melting point of 2250°C. What type of
crystal is formed?
.Gallium crystals are shiny and conduct electricity, gallium melts at 29.8 °C What type of crystal is it?
.Titanium bromide forms a soft orange-yellow crystal that melts at 39°C to give a non-conductive liquid
which boils at 230°C. What type of crystals does titanium bromine form?
Elemental phosphorus consists of soft white waxy crystals that are easily crushed and melt at 44°C The
solid does not conduct electricity. What type of crystals?
Problem Solving
According to the phase diagram for carbon dioxide, what phase(s) should exist at:
a) -60°C and 6 atm
b) -60°C and 2 atm
c) -40°C and 10 atm
d) -57°C and 5.2 atm
How can the phase diagram indicate that solid carbon dioxide is more dense than liquid?
Problem Solving
Tin(IV) chloride has soft crystals with a melting point of –30.2°C, the liquid is nonconducting. What type
of crystal is formed?
Elemental boron is a semiconductor, it is very hard and has a melting point of 2250°C. What type of
crystal is formed?
Gallium crystals are shiny and conduct electricity, gallium melts at 29.8 °C What type of crystal is it?
Problem Solving
Titanium bromide forms a soft orange-yellow crystal that melts at 39°C to give a non-conductive liquid
which boils at 230°C. What type of crystals does titanium bromine form?
Elemental phosphorus consists of soft white waxy crystals that are easily crushed and melt at 44°C The
solid does not conduct electricity. What type of crystals?
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