Chemical Bonds and Ionic Compounds
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C
HAPTER
6 –
C
HEMICAL
B
ONDS
Jennie L. Borders
W
ARM
-U
P
M
AR
. 11
1.
What is an ionic bond?
2.
What charge does an aluminum
ion have?
3.
Why are metals good
conductors of electricity and
heat?
S
ECTION
6.1 – I
ONIC
B
ONDS
When the
highest
occupied energy level of
an atom is filled with
electrons
, the atom
is stable and not likely to
react
.
The
noble gases
have stable electron
configurations with
eight
valence
electrons (or two in the case of
helium
).
S
TABLE
E
LECTRON
C
ONFIGURATIONS
The
chemical properties
of an element
depend on the number of
valence
electrons
.
An
electron dot diagram
is a model of an
atom in which each
dot
represents a
valence electron
.
I
ONIC
B
ONDS
Some elements achieve
stable electron
configurations
through the
transfer
of
electrons between atoms.
An atom that has a net
positive or
negative charge
is called an
ion
.
I
ONS
An ion with a
negative
charge is an
anion
.
Anions
like the Cl
-
ion are named by
adding the suffix
–ide
to the element
name. (Ex. Cl
-
=
chloride
)
An ion with a
positive
charge is a
cation
.
The name of a
cation
is the same as the
element name
. (Ex. Na
+
=
sodium
)
I
ON
C
HARGES
The
charges
that an ion has are based on
the number of
valence electrons
that an
element has.
All of the
elements
in the same
group
have the same
charge
.
I
ON
C
HARGES
Is it easier for lithium to gain 7 more
electrons or lose 1 electron?
What charge would lithium have?
lose 1 electron
+1
I
ON
C
HARGES
Is it easier for beryllium to gain 6 more
electrons or lose 2 electrons?
What charge would beryllium have?
lose 2 electrons
+2
I
ON
C
HARGES
Is it easier for boron to gain 5 more
electrons or lose 3 electrons?
What charge would boron have?
lose 3 electrons
+3
I
ON
C
HARGES
Is it easier for carbon to gain 4 more
electrons or lose 4 electrons?
What charge would carbon have?
lose or gain 4 electrons
+4 or -4
I
ON
C
HARGES
Is it easier for nitrogen to gain 3 more
electrons or lose 5 electrons?
What charge would nitrogen have?
gain 3 electrons
-3
I
ON
C
HARGES
Is it easier for oxygen to gain 2 more
electrons or lose 6 electrons?
What charge would oxygen have?
gain 2 electrons
-2
I
ON
C
HARGES
Is it easier for fluorine to gain 1 more
electron or lose 7 electrons?
What charge would fluorine have?
gain 1 electron
-1
I
ON
C
HARGES
Would neon want to gain or lose
electrons?
What charge would neon have?
No, it has a full energy level
0
I
ON
C
HARGES
Since
elements
in the same
group
have
the same number of
valence electrons
,
they all have the same
charge
.
F
ORMATION
OF
I
ONIC
B
ONDS
A
chemical bond
is the force that holds
atoms or ions
together as a unit.
An
ionic bond
is the force that holds
cations and anions
together.
An
ionic bond
forms when electrons are
transferred
from one atom to another.
F
ORMATION
OF
I
ONIC
B
ONDS
When an
ionic bond
is formed, electrons
are
transferred
until each atom has a full
outer
energy level
.
I
ONIC
C
OMPOUNDS
Compounds that contain
ionic bonds
are
ionic compounds
, which can be
represented by
chemical formulas
.
A
chemical formula
is a notation that
shows what
elements
a compound
contains and the
ratio
of the atoms or ions
of these
elements
in the compound.
C
RYSTAL
L
ATTICES
A
chemical formula
for an ionic compound
tells you the
ratio of the ions
in the
compound.
Solids
whose particles are arranged in a
lattice structure
are called
crystals
.
P
ROPERTIES
OF
I
ONIC
C
OMPOUNDS
Ionic compounds
tend to have
high
melting points (above 300
o
C).
Ionic compounds are
poor conductors
in
the
solid
state, but they can
conduct
heat
or electricity when they are
melted
.
Ionic compounds are
brittle
, so they
shatter
when struck by a hammer.
The properties of
ionic compounds
can be
explained by the strong
attractions
among
ions within a
crystal lattice
.
I
ONIC
C
OMPOUNDS
AND
E
LECTRICITY
S
ECTION
6.1 A
SSESSMENT
1.
When is an atom least likely to react?
2.
Describe one way an element can achieve
a stable electron configuration.
3.
What characteristic of ionic bonds can be
used to explain the properties of ionic
compounds?
4.
What will the ratio of ions be in any
compound formed from a Group 1 metal
and a Group 17 nonmetal?
S
ECTION
6.1 A
SSESSMENT
5.
Why do ionic compounds include at least
one metal?
6.
Based on their chemical formulas, which
of these compounds is not likely to be an
ionic compounds: KBr, SO
2
, or FeCl
3
?
W
ARM
-U
P
M
AR
. 12
1.
What charge do the elements in
Group 16 have?
2.
What are 3 properties of an ionic
compound?
3.
Name the following ions:
a. Ca
+2
b. Br
-
S
ECTION
6.2 – C
OVALENT
B
ONDING
A
covalent bond
is a chemical bond in
which two atoms
share
a pair of
valence
electrons
.
When two atoms share
one pair
of
electrons, the bond is called a
single bond
.
C
OVALENT
VS
I
ONIC
B
OND
M
OLECULES
OF
E
LEMENTS
A
molecule
is a neutral
group of atoms
that are joined together by one or more
covalent bonds
.
The
attractions
between the shared
electrons and the
protons
in each nucleus
hold the atoms together in a
covalent
bond
.
Many
nonmetal
elements exist as
diatomic molecules
. Diatomic means
two
atoms
. They are
H
2
, N
2
, O
2,
F
2
, Cl
2
, Br
2
,
and I
2
.
D
IATOMIC
E
LEMENTS
M
ULTIPLE
C
OVALENT
B
ONDS
When two atoms share
two pairs
of
electrons, the bond is called a
double
bond
.
When two atoms share
three pairs
of
electrons, the bond is called a
triple bond
.
S
ECTION
6.2 A
SSESSMENT
1.
What attractions hold atoms together in
a covalent bond?
2.
Which of these elements does not bond to
form molecules: oxygen, chlorine, neon,
or sulfur?
3.
Based on their electron dot diagrams,
what is the formula for the covalently
bonded compound of nitrogen and
hydrogen?
W
ARM
-U
P
M
AR
. 13
1.
What is a covalent bond?
2.
List the 7 diatomic elements.
3.
What is a molecule?
S
ECTION
6.3 – N
AMING
C
OMPOUNDS
AND
W
RITING
F
ORMULAS
The name of an
ionic compound
must
distinguish the
compound
from other ionic
compounds containing the same
elements
.
The
formula
of an ionic compound
describes the
ratio of the ions
in the
compound.
B
INARY
I
ONIC
C
OMPOUNDS
A
compound
made from
only
two
elements is a
binary compound
.
When naming an
ionic
compound
the name of
the
metal (cation)
does
not change and the
name of the
nonmetal
(anion)
has the suffix
–ide
.
Ex. MgBr
2
=
magnesium bromide
M
ETAL
WITH
M
ULTIPLE
I
ONS
Many
transition metals
form more than
one type of
ion
.
When a
metal
forms more than one ion,
the name of the ion contains a
roman
numeral
to indicate the
charge
of the ion.
Ex: Fe
+2
=
iron (II)
Fe
+3
=
iron (III)
P
OLYATOMIC
I
ONS
A
covalently
bonded group of
atoms
that
has a positive or negative
charge
and acts
as a unit is a
polyatomic ion
.
WRITING FORMULAS FOR
IONIC COMPOUNDS
Place the symbol of the
cation
first, followed by
the symbol of the
anion
.
Use
subscripts
to show
the
ratio
of the ions in
the
compound
.
Because all compounds
are
neutral
, the total
charges
on the cations
and anions must add up
to
zero
.
C
ROSSING
C
HARGES
To
balance the charges
in an ionic
compound, you can
cross
the charges if
they are not the
same
.
D
ESCRIBING
M
OLECULAR
C
OMPOUNDS
The name and formula of a
molecular
compound
describe the
type and number
of atoms in a molecule of the
compound
.
Molecular compounds
only contain
nonmetals
.
N
AMING
M
OLECULAR
C
OMPOUNDS
The name of the
first element
is the same.
The name of the
second element
ends in
the suffix
-ide
.
Prefixes
tell the number of
atoms
of each
element. A
prefix
is not used when the
first element
only has
1 atom
.
Ex. CO
2
=
carbon dioxide
P
REFIXES
1 = mono
6 = hexa
2 = di
7 = hepta
3 = tri
8 = octa
4 = tetra
9 = nona
5 = penta
10 = deca
W
RITING
M
OLECULAR
F
ORMULAS
Write the
symbols
for the elements in the
order the
elements
appear in the name.
The
prefixes
indicate the
number
of atoms
of each
element
in this molecule.
Ex: diphosphorus pentoxide =
P
2
O
5
S
ECTION
6.3 A
SSESSMENT
1.
What does the formula of an ionic
compound describe?
2.
What do the name and formula of a
molecular compound describe?
3.
What suffix is used to indicate an anion?
4.
Why are Roman numerals used in the
names of compounds that contain
transition metals?
5.
What is a polyatomic ion?
S
ECTION
6.3 A
SSESSMENT
6.
How is it possible for two different ionic
compounds to contain the same
elements?
7.
How many potassium ions are needed to
bond with a phosphate ion?
8.
What are the name of these ionic
compounds: LiCl, BaO, and Na
3
N?
9.
Name the molecular compounds with
these formulas: N
2
O
7
and CO.
10.
What is the formula for the ionic
compound formed from potassium and
sulfur?
S
ECTION
6.4 – T
HE
S
TRUCTURE
OF
M
ETALS
In a
metal
, valence electrons are
free
to
move among the atoms, so the
cations
are
surrounded by a
sea of electrons
.
A
metallic bond
is the attraction between
a
metal cation
and the shared
electrons
that surround it.
M
ETALLIC
B
ONDS
The
cations
in a metal form a
lattice
that
is held in place by strong
metallic bonds
between the cations and the surrounding
valence electrons
.
The more
valence electrons
an atom can
contribute to the shared pool, the
stronger
the metallic bond will be.
P
ROPERTIES
OF
M
ETALS
The
mobility of electrons
within a metal
lattice explains the fact that metals are
good
conductors and malleable
.
A
LLOYS
An
alloy
is a mixture of two or more
elements that have
metallic properties
.
SECTION
6.4 ASSESSMENT
1.
What holds metal ions together in a metal
lattice?
2.
What characteristic of a metallic bond
explains some of the properties of metals?
3.
Explain why the metallic bonds in some
metals are stronger than the bonds in other
metals.
4.
Why are metals good conductors of electric
current?
5.
Can two different elements form a metallic
bond together?
Ionic bonds are formed when atoms transfer electrons to achieve stable electron configurations, resulting in the creation of ions with positive or negative charges. Metals are good conductors due to their ability to easily lose electrons. The charges of ions depend on the number of valence electrons in an element. By understanding ion charges and electron configurations, we can predict the behavior of elements in forming compounds.
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Presentation Transcript
CHAPTER 6 CHEMICAL BONDS Jennie L. Borders
WARM-UP MAR. 11 1. What is an ionic bond? 2. What charge does an aluminum ion have? 3. Why are metals good conductors of electricity and heat?
SECTION 6.1 IONIC BONDS When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react. The noble gases have stable electron configurations with eight valence electrons (or two in the case of helium).
STABLE ELECTRON CONFIGURATIONS The chemical properties of an element depend on the number of valence electrons. An electron dot diagram is a model of an atom in which each dot represents a valence electron.
IONIC BONDS Some elements achieve stable electron configurations through the transfer of electrons between atoms. An atom that has a net positive or negative charge is called an ion.
IONS An ion with a negative charge is an anion. Anions like the Cl-ion are named by adding the suffix ide to the element name. (Ex. Cl-= chloride) An ion with a positive charge is a cation. The name of a cation is the same as the element name. (Ex. Na+= sodium)
ION CHARGES The charges that an ion has are based on the number of valence electrons that an element has. All of the elements in the same group have the same charge.
ION CHARGES Is it easier for lithium to gain 7 more electrons or lose 1 electron? What charge would lithium have? lose 1 electron +1
ION CHARGES Is it easier for beryllium to gain 6 more electrons or lose 2 electrons? What charge would beryllium have? lose 2 electrons +2
ION CHARGES Is it easier for boron to gain 5 more electrons or lose 3 electrons? What charge would boron have? lose 3 electrons +3
ION CHARGES Is it easier for carbon to gain 4 more electrons or lose 4 electrons? lose or gain 4 electrons What charge would carbon have? +4 or -4
ION CHARGES Is it easier for nitrogen to gain 3 more electrons or lose 5 electrons? What charge would nitrogen have? gain 3 electrons -3
ION CHARGES Is it easier for oxygen to gain 2 more electrons or lose 6 electrons? What charge would oxygen have? gain 2 electrons -2
ION CHARGES Is it easier for fluorine to gain 1 more electron or lose 7 electrons? What charge would fluorine have? gain 1 electron -1
ION CHARGES Would neon want to gain or lose electrons? What charge would neon have? No, it has a full energy level 0
ION CHARGES Since elements in the same group have the same number of valence electrons, they all have the same charge.
FORMATIONOF IONIC BONDS A chemical bond is the force that holds atoms or ions together as a unit. An ionic bond is the force that holds cations and anions together. An ionic bond forms when electrons are transferred from one atom to another.
FORMATIONOF IONIC BONDS When an ionic bond is formed, electrons are transferred until each atom has a full outer energy level.
IONIC COMPOUNDS Compounds that contain ionic bonds are ionic compounds, which can be represented by chemical formulas. A chemical formula is a notation that shows what elements a compound contains and the ratio of the atoms or ions of these elements in the compound.
CRYSTAL LATTICES A chemical formula for an ionic compound tells you the ratio of the ions in the compound. Solids whose particles are arranged in a lattice structure are called crystals.
PROPERTIESOF IONIC COMPOUNDS Ionic compounds tend to have high melting points (above 300oC). Ionic compounds are poor conductors in the solid state, but they can conduct heat or electricity when they are melted. Ionic compounds are brittle, so they shatter when struck by a hammer. The properties of ionic compounds can be explained by the strong attractions among ions within a crystal lattice.
SECTION 6.1 ASSESSMENT 1. When is an atom least likely to react? 2. Describe one way an element can achieve a stable electron configuration. 3. What characteristic of ionic bonds can be used to explain the properties of ionic compounds? 4. What will the ratio of ions be in any compound formed from a Group 1 metal and a Group 17 nonmetal?
SECTION 6.1 ASSESSMENT 5. Why do ionic compounds include at least one metal? 6. Based on their chemical formulas, which of these compounds is not likely to be an ionic compounds: KBr, SO2, or FeCl3?
WARM-UP MAR. 12 1. What charge do the elements in Group 16 have? 2. What are 3 properties of an ionic compound? 3. Name the following ions: a. Ca+2 b. Br-
SECTION 6.2 COVALENT BONDING A covalent bond is a chemical bond in which two atoms share a pair of valence electrons. When two atoms share one pair of electrons, the bond is called a single bond.
MOLECULESOF ELEMENTS A molecule is a neutral group of atoms that are joined together by one or more covalent bonds. The attractions between the shared electrons and the protons in each nucleus hold the atoms together in a covalent bond. Many nonmetal elements exist as diatomic molecules. Diatomic means two atoms. They are H2, N2, O2, F2, Cl2, Br2, and I2.
MULTIPLE COVALENT BONDS When two atoms share two pairs of electrons, the bond is called a double bond. When two atoms share three pairs of electrons, the bond is called a triple bond.
SECTION 6.2 ASSESSMENT 1. What attractions hold atoms together in a covalent bond? 2. Which of these elements does not bond to form molecules: oxygen, chlorine, neon, or sulfur? 3. Based on their electron dot diagrams, what is the formula for the covalently bonded compound of nitrogen and hydrogen?
WARM-UP MAR. 13 What is a covalent bond? List the 7 diatomic elements. What is a molecule? 1. 2. 3.
SECTION 6.3 NAMING COMPOUNDSAND WRITING FORMULAS The name of an ionic compound must distinguish the compound from other ionic compounds containing the same elements. The formula of an ionic compound describes the ratio of the ions in the compound.
BINARY IONIC COMPOUNDS A compound made from only two elements is a binary compound. When naming an ionic compound the name of the metal (cation) does not change and the name of the nonmetal (anion) has the suffix ide. Ex. MgBr2 = magnesium bromide
METALWITH MULTIPLE IONS Many transition metals form more than one type of ion. When a metal forms more than one ion, the name of the ion contains a roman numeral to indicate the charge of the ion. Ex: Fe+2 = iron (II) Fe+3 = iron (III)
POLYATOMIC IONS A covalently bonded group of atoms that has a positive or negative charge and acts as a unit is a polyatomic ion.
WRITING FORMULAS FOR IONIC COMPOUNDS Place the symbol of the cation first, followed by the symbol of the anion. Use subscripts to show the ratio of the ions in the compound. Because all compounds are neutral, the total charges on the cations and anions must add up to zero.
CROSSING CHARGES To balance the charges in an ionic compound, you can cross the charges if they are not the same.
DESCRIBING MOLECULAR COMPOUNDS The name and formula of a molecular compound describe the type and number of atoms in a molecule of the compound. Molecular compounds only contain nonmetals.
NAMING MOLECULAR COMPOUNDS The name of the first element is the same. The name of the second element ends in the suffix -ide. Prefixes tell the number of atoms of each element. A prefix is not used when the first element only has 1 atom. Ex. CO2 = carbon dioxide
PREFIXES 1 = mono 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa 7 = hepta 8 = octa 9 = nona 10 = deca
WRITING MOLECULAR FORMULAS Write the symbols for the elements in the order the elements appear in the name. The prefixes indicate the number of atoms of each element in this molecule. Ex: diphosphorus pentoxide = P2O5
SECTION 6.3 ASSESSMENT 1. What does the formula of an ionic compound describe? 2. What do the name and formula of a molecular compound describe? 3. What suffix is used to indicate an anion? 4. Why are Roman numerals used in the names of compounds that contain transition metals? 5. What is a polyatomic ion?
SECTION 6.3 ASSESSMENT 6. How is it possible for two different ionic compounds to contain the same elements? 7. How many potassium ions are needed to bond with a phosphate ion? 8. What are the name of these ionic compounds: LiCl, BaO, and Na3N? 9. Name the molecular compounds with these formulas: N2O7 and CO. 10. What is the formula for the ionic compound formed from potassium and sulfur?
SECTION 6.4 THE STRUCTURE OF METALS In a metal, valence electrons are free to move among the atoms, so the cations are surrounded by a sea of electrons. A metallic bond is the attraction between a metal cation and the shared electrons that surround it.
METALLIC BONDS The cations in a metal form a lattice that is held in place by strong metallic bonds between the cations and the surrounding valence electrons. The more valence electrons an atom can contribute to the shared pool, the stronger the metallic bond will be.
PROPERTIESOF METALS The mobility of electrons within a metal lattice explains the fact that metals are good conductors and malleable.
ALLOYS An alloy is a mixture of two or more elements that have metallic properties.
SECTION 6.4 ASSESSMENT 1. What holds metal ions together in a metal lattice? 2. What characteristic of a metallic bond explains some of the properties of metals? 3. Explain why the metallic bonds in some metals are stronger than the bonds in other metals. 4. Why are metals good conductors of electric current? 5. Can two different elements form a metallic bond together?
