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Chapter 5
Chemical Bonding and States of Matter
By the end of the chapter, you will recognize that
a. Having eight valence electrons is particularly desirable (“the octet rule”).
b. Atoms form bonds with other atoms to satisfy the octet rule.
c. The two major types of chemical bonds are ionic and covalent.
Chapter Learning Objectives
Chapter Learning Objectives (cont)
d. Electronegativity is the ability to attract shared electrons.
e. The type of bond formed between two atoms depends on their difference in electronegativity.
f. Ionic bonds form between atoms with a large difference in electronegativity (generally a metal and a nonmetal).
Chapter Learning Objectives (cont)
g. Nonpolar covalent bonds form between atoms with little difference in electronegativity (generally two nonmetals).
h. Polar covalent bonds form between atoms with intermediate difference in electronegativity.
i. Like dissolves like. That is, polar solutes dissolve in polar solvents.
Chapter Learning Objectives (cont)
j. Intermolecular forces hold the molecules of a material together in different states of matter.
k. Stronger intermolecular forces lead to higher melting and boiling temperatures.
l. The relative strengths of intermolecular forces generally follow the trend:
hydrogen bonds > dipole-dipole interactions > London forces
Chapter Outline
A. The Octet Rule The noble gases of Group VIIIA do not
typically form compounds with other atoms. Atoms with eight valence electrons are
particularly stable, an observation called the octet rule.
Atoms form bonds with other atoms to achieve a valence octet.
& B.
An octetis 8 valence electrons.is associated with the stability of the noble gases.
He is stable with 2 valence electrons (duet).
valence electrons
He 2 2
Ne 2, 8 8
Ar 2, 8, 8 8
Kr 2, 8, 14, 8 8
Octet Rule
ElectronicConfiguration of Noble Gases
Chapter Outline
C. Types of compounds
1. Ionic Attractions between oppositely charged
particles
2. Covalent Atoms share electron pairs.
Types of Compounds
Chapter Outline
Lewis Dot Structures (Review) The number of valence electrons is equal to the
group number for most of the main group elements.
In Lewis dot structures, the chemical symbol represents the nucleus and the core electrons and dots represent the valence electrons.
Lewis Dot Structures
Chapter Outline
1. Ionic Bonds Ionic compounds result from the loss of
electrons by one atom (usually a metal) and the gain of electrons by another atom (usually a nonmetal).
Ionic bonds arise from the attraction between particles with opposite charges (electrostatic forces); e.g., Na+ Cl-.
Ionic and Covalent Bonds
Atoms form octets
to become more stable.
by losing, gaining, or sharing valence electrons.
by forming ionic bonds or covalent bonds.
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:
Metals Form Positive Ions known as CationsMetals form positive ions (cations)
by a loss of their valence electrons.
with the electron configuration of the nearest noble gas.
that have fewer electrons than protons.
Group 1A metals ion 1+
Group 2A metals ion 2+
Group 3A metals ion 3+
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Formation of a Sodium Ion, Na+
Sodium achieves an octet by losing its one valenceelectron.
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2, 8, 1 2, 8
Charge of Sodium Ion, Na+
With the loss of its valence electron,the sodium ion has a +1 charge.
Sodium atom Sodium ion 11p+ 11p+
11e- 10e-
0 1+
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2, 8
Learning CheckA. The number of valence electrons in aluminum is
1) 1e-. 2) 2e-. 3) 3e-.
B. The change in electrons for octet requires a
1) loss of 3e-. 2) gain of 3e-. 3) a gain of 5e-.
C. The ionic charge of aluminum is
1) 3-. 2) 5-. 3) 3+.
D. The symbol for the aluminum ion is
1) Al3+. 2) Al3-. 3) Al+.
Solution A. The number of valence electrons in aluminum is
3) 3 e-.
B. The change in electrons for octet requires a1) loss of 3e-.
C. The ionic charge of aluminum is3) 3+.
D. The symbol for the aluminum ion is1) Al3+.
Formation of Negative Ions known as AnionsIn ionic compounds, nonmetals
achieve an octet arrangement.
gain electrons.
form negatively charged ions with 3-, 2-, or 1- charges.
Formation of a Chloride, Cl-
Chlorine achieves an octet by adding an electron to its valence electrons.
2, 8, 7 2, 8, 8
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Charge of a Chloride Ion, Cl-
By gaining one electron, the chloride ion has a -1 charge.
Chlorine atom Chloride ion
17p+ 17p+
17e- 18e-
0 1–
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Some Ionic Charges
I-
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A. The number of valence electrons in sulfur is
1) 4e-. 2) 6e-. 3) 8e-.
B. The change in electrons for octet requires a
1) loss of 2e-. 2) gain of 2e-. 3) a gain of 4e-.
C. The ionic charge of sulfur is
1) 2+. 2) 2-. 3) 4-.
Learning Check
A. The number of valence electrons in sulfur is
2) 6e-.
B. The change in electrons for octet requires a
2) gain of 2e-.
C. The ionic charge of sulfur is
2) 2-.
Solution
The balance of charges in Al2O3
Run the following web animations/movies.
5.1: Formation of Sodium Chloride
5.2: Sodium Metal Reacting with Chlorine Gas
5.3: Ion Formation
Ionic Compounds
Naming Ionic Compounds with Two Elements To name a compound
that contains two elements,
• identify the cation and anion.
• name the cation first followed by the name of the anion.
Charges of Representative Elements
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Names of Some Common Ions
•
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Complete the names of the following ions. Ba2+ Al3+ K+
_________ __________ _________
N3 O2 F
_________ __________ _________
P3 S2 Cl
_________ __________ _________
Learning Check
Ba2+ Al3+ K+
barium aluminum potassium
N3 O2 F
nitride oxide fluoride
P3 S2 Cl
phosphide sulfide chloride
Solution
Formula Ions Name
cation anion
NaCl Na+ Cl- sodium chloride
K2S K+ S2- potassium sulfide
MgO Mg2+ O2- magnesium oxide
CaI2 Ca2+ I- calcium iodide
Al2O3 Al3+ O2- aluminum oxide
Examples of Ionic Compounds with Two Elements
Write the names of the following compounds.
1) CaO ___________
2) KBr ___________
3) Al2O3 ___________
4) MgCl2___________
Learning Check
Write the names of the following compounds:
1) CaO calcium oxide
2) KBr potassium bromide
3) Al2O3 aluminum oxide
4) MgCl2 magnesium chloride
Solution
A polyatomic ion • is a group of atoms. • has an overall ionic charge.
Some examples of polyatomic ions are
NH4+ ammonium OH− hydroxide
NO3−
nitrate NO2−
nitrite
CO32− carbonate PO4
3− phosphate
HCO3− hydrogen carbonate
(bicarbonate)
Polyatomic Ions
Some Compounds with Polyatomic Ions
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
The names of common polyatomic anions
• end in ate.
NO3− nitrate PO4
3− phosphate
• with one oxygen less end in ite.
NO2− nitrite PO3
3− phosphite
• with hydrogen attached use the prefix hydrogen (or bi).
HCO3− hydrogen carbonate (bicarbonate)
HSO3− hydrogen sulfite (bisulfite)
Some Names of Polyatomic Ions
Names and Formulas of Common Polyatomic Ions
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Names and Formulas of Common Polyatomic Ions
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
• The positive ion is named first followed by the name of the polyatomic ion.
NaNO3 sodium nitrate
K2SO4 potassium sulfate
Fe(HCO3)3 iron(III) bicarbonate
or iron(III) hydrogen carbonate
(NH4)3PO3 ammonium phosphite
Naming Compounds with Polyatomic Ions
Chapter Outline2. Covalent Bonds
Covalent bonds are formed when two atoms share one or more electron pairs.
A molecule is the fundamental unit of a covalent compound.
When two atoms share one pair of electrons, the result is a single bond.
Two shared pairs of electrons is a double bond; three is a triple bond.
Covalent bonds form
• when atoms share electrons to complete octets.
• between two nonmetal atoms.
• between nonmetal atoms from Groups 4A(14), 5A(15), 6A(16), and 7A(17).
Covalent Bonds
Hydrogen Molecule
A hydrogen molecule
• is stable with two electrons (helium).
• has a shared pair of electrons.
Run the following web animations/movies.
5.4: Bond Length and Energy
5.5: Electrostatic Interactions Between Hydrogen Atoms
Forming Octets in Molecules
In a fluorine, F2,, molecule, each F atom
• shares one electron.
• attains an octet.
Carbon forms 4 covalent bonds
In a CH4, methane, molecule
• a C atom shares 4 electrons to attain an octet.
• each H shares 1 electron to become stable like helium.
Multiple Bonds
In nitrogen molecule, N2,
• each N atom shares 3 electrons.• each N attains an octet.• the bond is a multiple bond called a triple bond.• the name is the same as the element.
Naming Covalent Compounds
To name covalent compounds• STEP 1: Name the first
nonmetal as an element.
• STEP 2: Name the second nonmetal with an ide ending.
• STEP 3: Use prefixes to indicate the number of atoms (subscript) of each element.
Table5.12
What is the name of SO3?
1. The first nonmetal is S sulfur.
2. The second nonmetal is O named oxide.
3. The subscript 3 of O is shown as the prefix tri.
SO3 sulfur trioxide
The subscript 1 (for S) or mono is understood.
Naming Covalent Compounds
Name P4S3.
1. The first nonmetal P is phosphorus.
2. The second nonmetal S is sulfide.
3. The subscript 4 of P is shown as tetra.
The subscript 3 of S is shown as tri.
P4S3 tetraphosphorus trisulfide
Naming Covalent Compounds
Formulas and Names of Some Covalent Compounds
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Select the correct name for each compound.
A. SiCl4 1) silicon chloride
2) tetrasilicon chloride3) silicon tetrachloride
B. P2O5 1) phosphorus oxide
2) phosphorus pentoxide3) diphosphorus pentoxide
C. Cl2O7 1) dichlorine heptoxide
2) dichlorine oxide3) chlorine heptoxide
Learning Check
Select the correct name for each compound.
A. SiCl4 3) silicon tetrachloride
B. P2O5 3) diphosphorus pentoxide
C. Cl2O7 1) dichlorine heptoxide
Solution
Covalent bonds are subclassified as nonpolar or
polar
Predicting Compounds using Lewis Dot Structures Going back to the idea of Lewis dot
configuration as a good way to keep track of valence electrons for predicting structure of ionic/covalent compounds.
Ionic Compounds Magnesium Iodide using the crossover method to
determine the molecular formula and draw the structure using Lewis dot valence electrons.
Step 1: Forming the magnesium cation:
Mg2+Mg + 2e-
Step 2: Forming the iodide anion:
I + 1e- I
Step 3: Putting the ions together
We need 2 iodide anions to balance the +2 charge on the magnesium, as indicated by the formula MgI2
IMg2+I
Covalent Compounds
Covalent compounds between oxygen and hydrogen
Step 1: Determine how many bonds are formed by oxygen
Step 2: Determine how many hydrogen atoms are in the chemical formula (hydrogen forms a single bond)
Step 3: Draw the structure
Draw the structure for H2O
O6 valence e- 2 max bonds
O H
H
O H2
6 valence e-
and
1 valence e-H2O
H1 valence e- 1 bond each
Covalent Compounds
Covalent compounds between carbon and hydrogen
Step 1: Determine how many bonds are formed by carbon
Step 2: Determine how many hydrogen atoms are in the chemical formula (hydrogen forms a single bond)
Step 3: Draw the structure
Draw the structure for CH4
H1 valence e- 1 bond each
4 valence e- 4 max bondsC
H4
4 valence e-
and
1 valence e-
CH4
C H
H
C
H
H
Chapter Outline
d. Equal Sharing versus Unequal Sharing When two different kinds of atoms are bonded,
the electrons are usually shared unequally. When a bond exists between two identical kinds
of atoms, the electrons are shared equally. An atom with greater electronegativity has a
greater ability to attract shared electrons.
Electronegativity
Chapter Outline
d. Equal Sharing versus Unequal Sharing (cont)
The greater the difference in electronegativity between two atoms that are covalently bonded, the more polar is the bond.
Polar vs. Nonpolar Bonds
Paired molecules much different in electronegativity play tug of war
Credit: Courtesy of Julie Millard
Chapter Outline
j. States of Matter Review of Types of Bonds
1. Chemical bonds (intramolecular forces) hold atoms together.
2. The three types of chemical bonds are ionic, polar covalent, and nonpolar covalent.
3. Intermolecular forces hold molecules together.
Types of Bonds
Chapter Outline
j. States of Matter (cont) Particle Cohesion Determines Physical State
1. In general, the relative strengths of intermolecular forces follows the trend:
gases < liquids < solids Changes of State
Adding energy breaks intermolecular forces and causes molecules to change their state.
The stronger the intermolecular forces of a compound, the higher are the melting and boiling points.
Changes of State
Chapter Outlinek. Types of Intermolecular Forces within
Pure Substances London dispersion forces
A temporary dipole in one molecule can induce a dipole in a neighboring molecule.
The negative end of one temporary dipole can attract the positive end of an induced dipole; these attractions are called London dispersion forces.
London forces tend to be fairly weak.
Instantaneous dipoles from electron movements
London Dispersion Forces
Chapter Outline
Types of Intermolecular Forces within Pure Substances (cont) Dipole-dipole interactions
Dipole-dipole interactions exist between molecules with polar covalent bonds.
Dipole-dipole interactions are typically stronger than London dispersion forces.
Dipole-Dipole Interactions
Chapter Outline Types of Intermolecular Forces within
Pure Substances (cont) Hydrogen Bonds
Hydrogen bonds are a special type of dipole-dipole interaction.
Hydrogen bonds can occur when H is bonded to one of the highly electronegative atoms N, O, or F. An example is H2O.
Hydrogen bonds are typically quite strong.
Hydrogen Bonds in Water
Ice crystal lattice
Run the following web animations/movies.
5.6: Electric Current Conduction by Molten Salts
5.8a: Atomic Motion and Thermal Energy
5.9: Atomic Properties of Solids, Liquids, and Gases
Chapter Outline
i. Forming Solutions Like dissolves like
Ionic solutes often dissolve in polar solvents;e.g., NaCl dissolves in H2O.
Polar solutes generally dissolve in polar solvents; e.g., NH3 in H2O.
Nonpolar solutes generally do not dissolve well in polar solvents; e.g., oil in H2O.
Run the following web animations/movies.
5.10: Like Dissolves Like Solubility
NaCl Dissolving in H2O
Polar covalent molecules with dipoles can induce dipoles in nonpolar molecules
Why octane molecules and water don't mix
Oil and water do not mix
Credit: Visuals Unlimited
Chapter Outline
Emulsions Emulsifying agents are molecules that contain a
polar portion and a nonpolar region. Soap is an example of an emulsifying agent that
can form a suspension of a nonpolar material in a polar solvent (an “emulsion”).
Emulsification with Soap
Chapter Outlinel. Measuring Amounts in Solution
Solubility The maximum amount of a solute that dissolves in a
solvent Molarity
The amount of a solute dissolved in a solvent is its concentration.
Concentration is often measured in moles/liter, also called molarity (M).
Parts per million (ppm) The concentration of a dilute solution may be measured
in parts per million (grams of solute per million grams solution).
Solubilities of various Ionic Compounds in Water
Key Words
Chemical bonds Noble gases Octet rule Ionic compound Ion Covalent compound Lewis dot structures Core electrons Cation Anion Electrostatic forces
Chemical formula Lone pair Single bond Double bond Triple bond Isomers Nonpolar covalent bond Polar covalent bond Electronegativity Dipole Structure
Key Words
Intermolecular forces London dispersion forces Dipole-dipole interactions Hydrogen bonds Solution Solute Solvent Aqueous solution
Colloid Suspension Amphiphilic/
amphipathic Emulsion Solubility Concentration Molarity (M) Parts per million (ppm)