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Chapter 5
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Classification of Matter
Matter is organized by its components: elements, compounds, and
mixtures.
Ionic and Covalent Bonds
Atoms form octets
 to become more stable.
 by losing, gaining, or sharing
valence electrons.
 by forming ionic or covalent
bonds.
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Chapter 5, Section 1
3
Covalent Compounds
Covalent compounds are formed when nonmetals
share valence electrons forming a covalent bond.
Covalent compounds consist of molecules, which are
discrete groups of atoms, such as:
 water, H2O
 carbon dioxide, CO2
 glucose, C6H12O6
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2 H atoms + 1 O atom
1 C atom + 2 O atoms
6 C atoms + 12 H atoms
+ 6 O atoms
Chapter 5, Section 1
4
Ionic Compounds
Ionic compounds are formed when metal atoms
transfer electrons to nonmetal atoms resulting in the
formation of ionic bonds.
Ionic compounds we use every day include:
 table salt
NaCl
 baking soda
NaHCO3
 milk of magnesia
Mg(OH)2
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Chapter 5, Section 1
5
Ionic Compounds, Minerals
Precious and semiprecious gemstones are also
examples of ionic compounds called minerals.
Sapphires and rubies are made of aluminum oxide
(Al2O3), which is an ionic compound. Their brilliant
colors come from the presence of other metals such as
 chromium, which make rubies red and
 iron and titanium, which make sapphires blue
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Chapter 5, Section 1
6
Octet Rule
The octet rule is the tendency for atoms to share or transfer
electrons to obtain a stable configuration of 8 valence
electrons.
Octet Rule
The octet rule is associated with the stability of the
noble gases except for He, which is stable with 2
valence electrons (duet).
He 1s2
Valence Electrons
2
Ne 1s22s22p6
8
Ar 1s22s22p63s23p6
8
Metals Form Positive Ions
Metals form positive ions called
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 (1) metals
ion 1+
Group 2A (2) metals
ion 2+
Group 3A (3) metals
ion 3+
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Chapter 5, Section 1
9
Formation of a Sodium Ion, Na+
Sodium achieves an octet by losing its one valence
electron.
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Chapter 5, Section 1
10
Formation of Magnesium Ion, Mg2+
Magnesium achieves an octet by losing its two
valence electrons.
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Chapter 5, Section 1
11
Learning Check
1. What is the number of valence electrons in
aluminum?
A. 1 e–
B. 2 e–
C. 3 e–
2. What does aluminum require to acquire an
octet of electrons?
A. a loss of 3 e–
C. a gain of 5 e–
B. a gain of 3 e–
3. What is the charge of an aluminum ion?
A. 3–
B. 5–
C. 3+
4. What is the symbol for an aluminum ion?
A. Al3+
B. Al3–
C. Al+
Formation of Negative Ions
In ionic compounds, nonmetals
 achieve an octet arrangement.
 gain electrons.
 form negatively charged ions called anions with 3–, 2–,
or 1– charges.
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Chapter 5, Section 1
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Formation of a Chloride Ion, Cl–
Chlorine achieves an octet by adding one more electron
to its 7 valence electrons.
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Chapter 5, Section 1
17
Charge of a Chloride Ion, Cl–
By gaining one electron, the
chloride ion has a 1− charge.
charge
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Chapter 5, Section 1
18
Ionic Charge from Group
Numbers
Ions achieve the electron configuration of their
nearest noble gas by forming
 positive ions with a charge equal to its Group number.
Group 1A (1) = 1+
Group 2A (2) = 2+
Group 3A (3) = 3+
 negative ions with a charge obtained by subtracting 8 or
18 from its Group number.
Some Typical Ionic Charges
Group Numbers for Some Positive and
Negative Ions
Learning Check
1. What is the Group number for sulfur?
A. 4A (14)
B. 8A (18)
C. 6A (16)
2. What is the number of valence
electrons in sulfur?
A. 4 e−
B. 6 e−
C. 8 e−
3. To acquire an octet, what does
sulfur require?
A. gain of 2 e− B. loss of 2 e−
C. a gain of 4 e−
4.
What is the charge of sulfur ions?
A. 2+
B. 2−
C. 4−
Ionic Compounds
Ionic compounds
 consist of positive and negative ions.
 have attractive forces between the positive and
negative ions called ionic bonds.
 have high melting and boiling points.
 are solid at room temperature.
Formulas of Ionic Compounds
The chemical formula of an ionic compound
represents the element symbols and subscripts, which
represent the lowest whole-number ratio of ions.
In the formula of an ionic compound,
 the sum of positively and negatively charged ions is
always zero.
 the charges are balanced.
Charge Balance for NaCl, “Salt”
In NaCl,
 a Na atom loses its valence electron.
 a Cl atom gains an electron.
 the symbol of the metal (sodium) is written first,
followed by the symbol of the nonmetal (chlorine).
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Chapter 5, Section 1
28
Charge Balance In MgCl2
In MgCl2,
 a Mg atom loses two valence electrons.
 two Cl atoms gain one electron each.
 subscripts indicate the number of ions needed to give
charge balance.
 the symbol of the metal (magnesium) is written first,
followed by the symbol of the nonmetal (chlorine).
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Chapter 5, Section 1
29
Writing Ionic Formulas from Charge
Balance
Charge balance is used to write the formula for
sodium nitride, a compound containing Na+ and N3−.
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Chapter 5, Section 1
30
Charge Balance in Na2S
In sodium sulfide, Na2S,
 two Na atoms lose one valence electron each.
 one S atom gains two electrons.
 subscripts show the number of ions needed to give
charge balance.
The group of ions with the lowest ratio of ions in an
ionic compound is called a formula unit .
Formula from Ionic Charges
Write the ionic formula of the compound containing Ba2+
and Cl−.
 Write the symbols of each ion.
Ba2+ Cl−
 Balance the charges.
Ba2+ Cl− (two Cl needed)
Cl−
 Write the metal first, followed by the nonmetal,
,
using a subscript to represent the number of
. Cl−
ions.
BaCl2
Learning Check
Select the correct formula for each of the following ionic
compounds.
1. Na+ and S2–
A. NaS
B. Na2S
C. NaS2
2. Al3+ and Cl–
A. AlCl3
B. AlCl
C. Al3Cl
3. Mg2+ and N3–
A. MgN
B. Mg2N3
C. Mg3N2
Naming and Writing an Ionic Formula
The name of an ionic compound
 is made up of 2 elements.
 has the name of the metal ion written first.
 has the name of the nonmetal ion written second using
the first syllable of its element name. followed by ide.
 has a space separating the name of the metal and
nonmetal.
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Chapter 5, Section 1
36
Charges of Representative Elements
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Chapter 5, Section 3
37
Naming Mg3N2
Step 1 Identify the cation and anion.
The cation from Group 2A (2) is Mg2+, and
the anion from Group 5A (15) is N3−.
Step 2 Name the cation by its element name.
Cation: Mg2+ is magnesium
Step 3 Name the anion by using the first syllable of
its element name followed by ide.
Anion: nitrogen becomes nitride, N3−
Step 4 Write the name for the cation first and the
name for the anion second.
Mg3N2 is magnesium nitride.
Practice Naming
• MgCl2
• Na2S
• K3N