South Pasadena • AP Chemistry
Name
10 ▪ States of Matter
Period
10.1 LESSON
–
Date
SOLIDS
AND IMFS
Types of Solids
Example 1: For each of the following compounds, (1) determine the type of solid it forms, (2) identify the interparticle forces in the solid, and (3) sketch a sample unit cell for the solid.
(a) Diamond, C
(c) Calcium oxide, CaO
Ca2+
O2−
C
C
Network covalent
Ionic solid,
Ca2+
O2−
C
C
solid, covalent bonds
ionic bonds
C
(b) Copper, Cu
Metallic solid,
Metallic bonds (sea
of electrons)
O2−
C
C
2+
Cu2+
Cu2+
Cu
Cu2+
(d) Sugar, C12H22O11
Molecular solid, IMFs
(here, dipole-dipole)
Ca2+
C12H22O11
C12H22O11
Cu2+



C12H22O11
C12H22O11
C12H22O11
Cu2+
O2−
Ca2+
C
C12H22O11
Cu2+
Cu2+
C12H22O11
C12H22O11
Which is expected to have the lowest melting point temperature? Why?
Sugar (molecular solid) because it’s held by weak IMFs.
(Sugar - 186°C, copper - 1085°C, CaO - 2572°C,diamond - 4727°C)
Which is/are expected to conduct electricity? Why?
Cu (metallic solid) as a solid; CaCl2 (ionic solid) as aqueous or molten.
Summarize the four types of solids, how they are classified, and the inter-particle forces involved.
Type
Lattice Particle
Inter-Particle Forces
Metallic Solids
Between metal atoms
Metallic Bonds (sea of electrons)
Ionic Solids
Between cations/anions of ionic compounds
Ionic Bonds
Network Solids
Between non-metal atoms (e.g. C, Si, SiO2)
Covalent Bonds
Molecular Solids Between molecules of covalent compounds
Inter-molecular Forces (IMFs)
Ionic Solids
Example 2: Arrange the following solids from expected lowest to highest melting points: NaCl, MgO, BaO.
k·q1·q2
Coulomb’s Law (F = d2 ) states that strength of attraction between charged species relate directly to
electric charges and inversely to the square of the size. Here, melting points are NaCl (801°C) < BaO
(1923°C) < MgO (2852°C). Na+/Cl− has the smallest charges, so NaCl has the lowest MP; since Ba2+ is
larger than Mg2+, BaO has lower MP than MgO. Compare lattice energies – energy released when 1 mole of
an ionic compound is formed from ions – NaCl (788 kJ/mol) < BaO (3029 kJ/mol) < MgO (3795 kJ/mol).
Example 3: A sample of NaCl was hit, resulting in cleavage and brittleness.
Draw a particulate representation of the crystal before and after the impact.
Ionic solids form crystals of cations and anions held by strong ionic
bonds, so they are hard. When they are hit, the oppositely charged ions
are no longer aligned, and the repulsions between same-charged ions
repel each other resulting in cleavage and brittleness.
Metallic Solids and Alloys
Example 4: List the general properties of metallic solids. How do electrons contribute to these properties?
Electrical conductor because sea of electrons delocalized and free to move.
Malleable and ductile because deforming the solid does not change the environment around the metal cation.
Alloys are mixtures of a metallic solid with another element to modify the properties of the metallic solid.
Type of Alloy
Size of Elements
Arrangement of Atoms
Modified Properties
Examples
Atoms of the smaller element Rigidity of lattice increases,
Interstitial
Elements with
fills the spaces between
decreasing malleability and Steel (Fe + C)
Alloy
different radii.
atoms of the larger element.
ductility.
Density is between that of the
Substitutional Elements with
Added element replaces
two elements. Less malleable Brass (Cu + Zn)
Alloy
comparable radii.
atoms of other element.
and ductile than pure metal.
Example 5: Draw a particulate representation of the steel and brass.
Steel
Brass
O
O
Zn
O
Zn
Zn
Zn

Zn
Zn
Zn
O
Zn
Zn
Zn
Zn
O
Zn
Zn
Zn
Zn
O
Zn
Cu
Zn
Zn
Zn
O
Zn
Zn
Zn
Cu
Cu
Cu
Zn
Cu
Zn
Cu
Cu
Cu
Cu
Cu
Cu
Zn
Cu
Zn
Cu
Cu
Cu
Cu
Zn
Cu
The surface of steel reacts with oxygen to form an inert oxide layer. Sketch the results of this process above.
Network Covalent Solids
 Network covalent solids are
usually of elements in the carbon
family because they can form
four bonds.
 Network solids typically have
high (low/high) melting points
because they are held by
covalent bonds, and
are rigid and hard because these
bond angles are fixed.
 Graphite is an allotrope of carbon that form sheets of two-dimensional networks. Unlike other network
covalent solids, graphite is soft (hard/soft) because the layers held by LDFs slide easily past each other.
 Silicon’s conductivity increases as the temperature increases.
o Doping Si with a Family 15 element (e.g. P, As) creates an n-type semiconductor, in which the extra
electron is allowed to conduct electricity.
o Doping Si with a Family 13 element (e.g. B, Al, or Ga) creates a p-type semiconductor, in which
movement of electrons into a positive hole conducts electricity.
Molecular Solids and Inter-Molecular Forces
Example 6: For each of the following compounds, (1) identify the type of inter-molecular force involved, and
(2) sketch the interaction between two molecules.
(a) He
London dispersion forces
(c) HCl
Dipole-dipole interactions
He
(b) O2
H − Cl
He
London dispersion forces
O=O
O=O
(d) HF
H−F
H − Cl
Hydrogen bonding
H−F

Arrange the compounds from expected lowest to highest melting point temperature.
He (−272°C) < O2 (−219°C) < HCl (−114) < HF (−84°)

Summarize the three types of IMFs and the role of electrons involved in each one.
London Dispersion Forces
e− cloud polarized to form weak, induced dipole
More e− = stronger LDF
Strongest IMF in non-polar compounds
Dipole-dipole Interactions
Attraction between opposite poles of a polar compound
Hydrogen bonding
Strong dipole-dipole interactions in which H is pulled by small,
high EN atoms (N, O, F).