Chapter 8: Covalent Bonding 8.1 Molecular Compounds

Chapter 8: Covalent Chapter 8: Covalent BondingBonding

8.1 Molecular 8.1 Molecular CompoundsCompounds

Molecules and Molecular Molecules and Molecular CompoundsCompounds

• In nature, matter In nature, matter takes many forms. takes many forms. The noble gases, The noble gases, including helium including helium and neon, are and neon, are monatomic. That monatomic. That means they exist means they exist as single atoms.as single atoms.

8.1


•Some compounds are so Some compounds are so different from ionic compounds different from ionic compounds that attractions between ions fail that attractions between ions fail to explain their bonding.to explain their bonding.

•The atoms held together by The atoms held together by sharing electrons are joined sharing electrons are joined by a by a covalent bondcovalent bond..

8.1


•A A moleculemolecule is a neutral group of is a neutral group of atoms joined together by covalent atoms joined together by covalent bonds. Air contains oxygen bonds. Air contains oxygen molecules.molecules.

•A A diatomic moleculediatomic molecule is a is a molecule consisting of two atoms. molecule consisting of two atoms. An oxygen molecule is a diatomic An oxygen molecule is a diatomic molecule.molecule.

8.1


•A compound composed of A compound composed of molecules is called a molecules is called a molecular compoundmolecular compound. Water . Water and carbon monoxide are and carbon monoxide are molecular compounds.molecular compounds.

8.1

Molecules and Molecular Molecules and Molecular ChangesChanges

•Molecular compounds tend to Molecular compounds tend to have relatively lower melting have relatively lower melting and boiling points than ionic and boiling points than ionic compounds.compounds.

8.1

Molecular FormulasMolecular Formulas8.1

•A A molecular formulamolecular formula is the is the chemical formula of a chemical formula of a molecular compound.molecular compound.–A molecular formula A molecular formula shows how many atoms shows how many atoms of each element a of each element a molecule contains.molecule contains.

• 1.1. Compared to ionic compounds, molecular Compared to ionic compounds, molecular compounds tend to have relativelycompounds tend to have relatively

a) low melting points and high boiling points.a) low melting points and high boiling points.

b) low melting points and low boiling points.b) low melting points and low boiling points.

c) high melting points and high boiling point.c) high melting points and high boiling point.

d) high melting points and low boiling points.d) high melting points and low boiling points.

8.1 Section Quiz.8.1 Section Quiz.

– 2.2. A molecular compound usually consists A molecular compound usually consists of of

a) a) two metal atoms and a nonmetal two metal atoms and a nonmetal atom.atom.

b) b) two nonmetal atoms and a metal two nonmetal atoms and a metal atom.atom.

c) c) two or more metal atoms.two or more metal atoms.

d)d) two or more nonmetal atoms.two or more nonmetal atoms.

8.1 Section Quiz8.1 Section Quiz


– 3.3. A molecular formula showsA molecular formula shows

a) how many atoms of each element a) how many atoms of each element a a molecule contains.molecule contains.

b) a molecule's structure.b) a molecule's structure.

c) which atoms are bonded together.c) which atoms are bonded together.

d) how atoms are arranged in space.d) how atoms are arranged in space.

8.2 The Nature of Covalent 8.2 The Nature of Covalent BondingBonding

8.2The Octet Rule in Covalent The Octet Rule in Covalent BondingBonding

•In covalent bonds, electron In covalent bonds, electron sharing usually occurs so that sharing usually occurs so that atoms attain the electron atoms attain the electron configurations of noble gases.configurations of noble gases.

Single Covalent BondsSingle Covalent Bonds•Two atoms held together by Two atoms held together by

sharing a pair of electrons are sharing a pair of electrons are joined by a single covalent bond.joined by a single covalent bond.

8.2

8.2

Single Covalent BondsSingle Covalent Bonds•An electron dot structure An electron dot structure such as H:H represents the such as H:H represents the shared pair of electrons of the shared pair of electrons of the covalent bond by two dots.covalent bond by two dots.–A structural formula A structural formula represents the covalent represents the covalent bonds by dashes and shows bonds by dashes and shows the arrangement of the arrangement of covalently bonded atoms.covalently bonded atoms.

• The The halogenhalogens form s form single single covalent covalent bonds in bonds in their their diatomic diatomic moleculmolecules. es. Fluorine Fluorine is one is one exampleexample..

8.2

8.2

Single Covalent BondsSingle Covalent Bonds

•A pair of valence electrons A pair of valence electrons that is not shared between that is not shared between atoms is called an atoms is called an unshared unshared pairpair, also known as a lone , also known as a lone pair or a nonbonding pair.pair or a nonbonding pair.

Single Covalent BondsSingle Covalent Bonds•The hydrogen and oxygen atoms The hydrogen and oxygen atoms

attain noble-gas configurations by attain noble-gas configurations by sharing electrons.sharing electrons.

Single Covalent BondsSingle Covalent Bonds•The ammonia molecule has one The ammonia molecule has one

unshared pair of electrons.unshared pair of electrons.

8.2

•MethanMethane has no e has no unshareunshared pairs d pairs of of electronelectrons.s.

8.2

Covalent MoleculesCovalent Molecules

•Hydrogen shares 2 Hydrogen shares 2 electrons (electrons (duet ruleduet rule))

•Ex: HEx: H22

• HH HH → H → H HH•Helium does not form Helium does not form bonds because its valence bonds because its valence orbital is filled (He )orbital is filled (He )

Covalent MoleculesCovalent Molecules

•Other nonmetals require 8 Other nonmetals require 8 valence electrons (valence electrons (octet octet rulerule))

•Ex: FEx: F22

• FF FF → F → F FFBonding Pair Lone Pair

Steps for Lewis StructuresSteps for Lewis Structures1)1) Add up all valence electrons Add up all valence electrons

for all atomsfor all atoms

2)2) Use one pair to form bonds Use one pair to form bonds between each pair of atoms between each pair of atoms (use a line to represent 2 (use a line to represent 2 dots)dots)

3)3) Arrange remaining electrons Arrange remaining electrons to satisfy duet or octet ruleto satisfy duet or octet rule

Drawing Lewis DiagramsDrawing Lewis Diagrams

•CFCF44

8.1

Section AssessmentSection Assessment

Draw Lewis structures for:a)H2Sb)SiH4

8.2Double and Triple Covalent Double and Triple Covalent BondsBonds

•Atoms form double or triple Atoms form double or triple covalent bonds if they can covalent bonds if they can attain a noble gas structure attain a noble gas structure by sharing two pairs or three by sharing two pairs or three pairs of electrons.pairs of electrons.

8.2Double and Triple Covalent Double and Triple Covalent BondsBonds

•A bond that involves two A bond that involves two shared pairs of electrons is a shared pairs of electrons is a double covalent bonddouble covalent bond..

•A bond formed by sharing A bond formed by sharing three pairs of electrons is a three pairs of electrons is a triple covalent bondtriple covalent bond..

Double and Triple Covalent Double and Triple Covalent BondsBonds

8.2

•Carbon dioxide is an example Carbon dioxide is an example of a triatomic molecule.of a triatomic molecule.

8.2

Example Example

•CHCH22OO•formaldehydeformaldehyde

PracticePractice

• CC22HH22

• Carbon disulfideCarbon disulfide

Polyatomic IonsPolyatomic Ions

•A A polyatomic ionpolyatomic ion, such as NH, such as NH44++, ,

is a tightly bound group of atoms is a tightly bound group of atoms that has a positive or negative that has a positive or negative charge and behaves as a unit. charge and behaves as a unit.

•Most plants need Most plants need nitrogen that is nitrogen that is already combined already combined in a compound to in a compound to grow. grow.

8.2

Polyatomic IonsPolyatomic Ions•ClOClO44

--

•NHNH44++

Polyatomic IonsPolyatomic Ions

Example: CNExample: CN- -

8.2

Section Section AssessmeAssessmentnt

Draw the Lewis structure:1)ClO3

-

2)ClO4-

3)HCO3-

Bond Dissociation EnergiesBond Dissociation Energies

•The energy required to break the The energy required to break the bond between two covalently bond between two covalently bonded atoms is known as the bonded atoms is known as the bond dissociation energybond dissociation energy..–A large bond dissociation A large bond dissociation energy corresponds to a strong energy corresponds to a strong covalent bond.covalent bond.

8.2

ResonanceResonance•A A resonance structureresonance structure is a is a

structure that occurs when it is structure that occurs when it is possible to draw two or more valid possible to draw two or more valid electron dot structures that have electron dot structures that have the same number of electron pairs the same number of electron pairs for a molecule or ion.for a molecule or ion.

8.2

Resonance StructuresResonance Structures SO3

Exceptions to the Octet RuleExceptions to the Octet Rule

•The octet rule cannot be satisfied The octet rule cannot be satisfied in molecules whose total number in molecules whose total number of valence electrons is an odd of valence electrons is an odd number. There are also number. There are also molecules in which an atom has molecules in which an atom has fewer, or more, than a complete fewer, or more, than a complete octet of valence electrons.octet of valence electrons.

8.2

Exceptions to the Octet RuleExceptions to the Octet Rule•Two electron dot structures can Two electron dot structures can

be drawn for the NObe drawn for the NO22 molecule. molecule.

8.2

Exceptions to the Octet RuleExceptions to the Octet Rule•The electron dot structure for The electron dot structure for

PClPCl55 can be written so that can be written so that phosphorus has ten valence phosphorus has ten valence electrons.electrons.

8.2

Drawing Lewis DiagramsDrawing Lewis Diagrams•BeClBeCl22

Practice ProblemsPractice Problems

• 1) BH1) BH33

• 2) PF2) PF66--

• 3) ClF3) ClF33

– 1. 1. In covalent bonding, atoms In covalent bonding, atoms attain the configuration of noble attain the configuration of noble gases bygases by

a) losing electrons.a) losing electrons.

b) gaining electrons.b) gaining electrons.

c) transferring electrons.c) transferring electrons.

d) sharing electrons.d) sharing electrons.


8.2 Section Quiz8.2 Section Quiz– 2. 2. Electron dot diagrams are superior to Electron dot diagrams are superior to

molecular formulas in that they molecular formulas in that they

a) show which electrons are shared.a) show which electrons are shared.

b) indicate the number of each kind of b) indicate the number of each kind of atom in the molecule.atom in the molecule.

c) show the arrangement of atoms in c) show the arrangement of atoms in the molecule.the molecule.

d) are easier to write or draw.d) are easier to write or draw.

– 3. 3. Which of the following molecules Which of the following molecules would contain a bond formed when would contain a bond formed when atoms share three pairs of electrons?atoms share three pairs of electrons?

a) Sea) Se22

b) Asb) As22

c) Brc) Br22

d) Ted) Te22


8.3 Bonding Theories8.3 Bonding Theories

8.3

Molecular Orbitals

•When two atoms combine, the molecular orbital model assumes that their atomic orbitals overlap to produce molecular orbitals, or orbitals that apply to the entire molecule.

8.3

Molecular Orbitals

–Just as an atomic orbital belongs to a particular atom, a molecular orbital belongs to a molecule as a whole.

•A molecular orbital that can be occupied by two electrons of a covalent bond is called a bonding orbital.

8.3

Molecular Orbitals

–Sigma Bonds

•When two atomic orbitals combine to form a molecular orbital that is symmetrical around the axis connecting two atomic nuclei, a sigma bond is formed.

8.3

Molecular Orbitals

•When two fluorine atoms combine, the p orbitals overlap to produce a bonding molecular orbital. The F—F bond is a sigma bond.

8.3

Molecular Orbitals

–Pi Bonds

•In a pi bond (symbolized by the Greek letter ), the bonding electrons are most likely to be found in sausage-shaped regions above and below the bond axis of the bonded atoms.

8.3

VSEPR TheoryVSEPR Theory

•The valence-shell electron-The valence-shell electron-pair repulsion theory, or pair repulsion theory, or VSEPR theoryVSEPR theory, explains the , explains the three-dimensional shape of three-dimensional shape of methane.methane.

8.3

VSEPR TheoryVSEPR Theory

–According to VSEPR theory, According to VSEPR theory, the repulsion between the repulsion between electron pairs causes electron pairs causes molecular shapes to adjust molecular shapes to adjust so that the valence-so that the valence-electron pairs stay as far electron pairs stay as far apart as possible.apart as possible.

LinearLinear

•Total pairs: 2Total pairs: 2

•Shared pairs: 2Shared pairs: 2

•Lone pairs: 0Lone pairs: 0

•Bond Angle: 180Bond Angle: 180°°

•Hybridization: spHybridization: sp

•Ex: BeClEx: BeCl22

Trigonal PlanarTrigonal Planar

•Total Pairs: 3Total Pairs: 3

•Shared Pairs: 3Shared Pairs: 3

•Lone Pairs: 0Lone Pairs: 0

•Bond Angle: 120Bond Angle: 120°°

•Hybridization: spHybridization: sp22

•Ex: AlClEx: AlCl33

TetrahedralTetrahedral•Total Pairs: 4Total Pairs: 4




Trigonal PyramidalTrigonal Pyramidal• Total Pairs: 4Total Pairs: 4

• Shared Pairs: 3Shared Pairs: 3

• Lone Pairs: 1Lone Pairs: 1

• Bond Angle: 107.3Bond Angle: 107.3°°

• Hybridization: spHybridization: sp33

Bent (V-shaped)Bent (V-shaped)

•Total Pairs: 4Total Pairs: 4




•Bond Angle: 104.5Bond Angle: 104.5°°

•Ex: HEx: H22OO

Trigonal BipyramidalTrigonal Bipyramidal

• Total pairs: 5Total pairs: 5

• Shared pairs: 5Shared pairs: 5

• Lone pairs: 0Lone pairs: 0

• Hybridization: spHybridization: sp33dd

• Example: NbBrExample: NbBr55

• Bond angles: equatorial is 120° and Bond angles: equatorial is 120° and axial is 90°axial is 90°

OctahedralOctahedral

• Total pairs: 6Total pairs: 6

• Bonding pairs: 6Bonding pairs: 6

• Lone pairs: 0Lone pairs: 0

• Hybridization: spHybridization: sp33dd22

• Example SFExample SF66

• Bond angles: 90°Bond angles: 90°

•PFPF33

ExamplesExamples

•COCO22

ExamplesExamples

Draw Lewis Structure and Draw Lewis Structure and predict Shape of:predict Shape of:

•1) NH1) NH33

•2) Cl2) Cl22OO

•3) N3) N22OO

•4) H4) H22SeSe

•5) ClO5) ClO44--

•6) NH6) NH44++

•7) SO7) SO442-2-

•8) NF8) NF33

•9) H9) H22SS

•10) ClO10) ClO33--

•11) BeF11) BeF22

•12) NO12) NO33--

Hybrid Orbitals

•Orbital hybridization provides information about both molecular bonding and molecular shape.–In hybridization, several atomic orbitals mix to form the same total number of equivalent hybrid orbitals.

• http://mhhe.com/physsci/chemistry/essentialchemistry/flash/hybrv18.swf

8.3

http://mhhe.com/physsci/chemistry/essentialchemistry/flash/hybrv18.swf

8.3 Section Quiz.8.3 Section Quiz.– 1.1. VSEPR theory enables prediction of 3-VSEPR theory enables prediction of 3-

dimensional molecular shape because dimensional molecular shape because the valence electron pairs the valence electron pairs

a) are attracted to each other.a) are attracted to each other.

b) form molecules with only four b) form molecules with only four possible shapes.possible shapes.

c) stay as far apart as possible.c) stay as far apart as possible.

d) always form tetrahedral shapes.d) always form tetrahedral shapes.

– 2. Orbital hybridization provides information about

•a) both molecular bonding and molecular shape.

•b) both molecular bonding and bond energy.

•c) neither molecular bonding nor molecular shape.

•d) neither molecular bonding nor bond energy.

8.3 Section Quiz.

8.4 Polar Bonds and 8.4 Polar Bonds and MoleculesMolecules

8.4

Bond PolarityBond Polarity

•When the atoms in a bond pull When the atoms in a bond pull equally (as occurs when equally (as occurs when identical atoms are bonded), identical atoms are bonded), the bonding electrons are the bonding electrons are shared equally, and the bond shared equally, and the bond is a is a nonpolar covalent nonpolar covalent bondbond..

8.4

Bond PolarityBond Polarity•The chlorine atom attracts the The chlorine atom attracts the

electron cloud more than the electron cloud more than the hydrogen atom does.hydrogen atom does.

8.4Bond PolarityBond Polarity•A A polar covalent bondpolar covalent bond, known also as a , known also as a

polar bond, is a covalent bond between polar bond, is a covalent bond between atoms in which the electrons are shared atoms in which the electrons are shared unequally. unequally. –The more electronegative atom attracts The more electronegative atom attracts electrons more strongly and gains a slightly electrons more strongly and gains a slightly negative charge. The less electronegative negative charge. The less electronegative atom has a slightly positive charge.atom has a slightly positive charge.

+ -

• Polar Covalent BondPolar Covalent Bond

Bond PolarityBond Polarity8.4

Electronegativity difference Electronegativity difference ((∆EN)∆EN)• Calculate the electronegativity difference Calculate the electronegativity difference

and tell the type of bond formed between and tell the type of bond formed between sulfur and each of the following: sulfur and each of the following: hydrogen, cesium, and chlorine. In each hydrogen, cesium, and chlorine. In each pair which atom will be more negative?pair which atom will be more negative?

• Use electronegativity differences to Use electronegativity differences to classify bonding between chlorine and classify bonding between chlorine and calcium, oxygen and bromine. In each calcium, oxygen and bromine. In each pair which atom will be more negative?pair which atom will be more negative?

Conceptual Problem 8.3Conceptual Problem 8.3

•Tell type of bond (nonpolar, polar Tell type of bond (nonpolar, polar or ionic) that will form between or ionic) that will form between the following pairs of atoms:the following pairs of atoms:–N and HN and H–F and FF and F–Ca and ClCa and Cl–Al and ClAl and Cl

PracticePractice- tell type of bond- tell type of bond

•H and BrH and Br

•Cl and FCl and F

•K and ClK and Cl

•Li and OLi and O

•C and OC and O

•Br and BrBr and Br

Dipole Moments in Polar Dipole Moments in Polar MoleculesMolecules

•H FH F

•δδ++ δδ--

Use an arrow to represent the dipole character that points toward the partial negative end

Determining Molecular Determining Molecular PolarityPolarity•Nonpolar MoleculesNonpolar Molecules

–Dipole moments are Dipole moments are symmetrical and symmetrical and cancel out.cancel out.

BF3

F

F F

B

Determining Molecular Determining Molecular PolarityPolarity

•Polar MoleculesPolar Molecules–Dipole moments are Dipole moments are asymmetrical and don’t cancel .asymmetrical and don’t cancel .

netdipolemoment

H2OH H

O

CHCl3

H

Cl ClCl

Determining Molecular Determining Molecular PolarityPolarity

•Therefore, polar molecules Therefore, polar molecules have...have...–asymmetrical shape (lone asymmetrical shape (lone pairs) or pairs) or

–asymmetrical atomsasymmetrical atomsnetdipolemoment

Polar MoleculesPolar Molecules

•In a In a polar moleculepolar molecule, one end , one end of the molecule is slightly of the molecule is slightly negative and the other end is negative and the other end is slightly positive. slightly positive.

•A molecule that has two poles is A molecule that has two poles is called a dipolar molecule, or called a dipolar molecule, or dipoledipole..

8.4

Polar MoleculesPolar Molecules•A hydrogen chloride molecule is a A hydrogen chloride molecule is a

dipole.dipole.

8.4

8.4Attractions Between Attractions Between MoleculesMolecules

•Intermolecular attractions Intermolecular attractions are weaker than either are weaker than either ionic or covalent bonds.ionic or covalent bonds.–These attractions are These attractions are responsible for responsible for determining whether a determining whether a molecular compound is a molecular compound is a gas, a liquid, or a solid at gas, a liquid, or a solid at a given temperature.a given temperature.

Attractions Between Attractions Between MoleculesMolecules

–Van der Waals ForcesVan der Waals Forces

•The two weakest attractions The two weakest attractions between molecules are between molecules are collectively called collectively called van der van der Waals forces,Waals forces, named after named after the Dutch chemist Johannes the Dutch chemist Johannes van der Waals (1837–1923).van der Waals (1837–1923).

8.4


•Dipole Dipole interactionsinteractions occur when occur when polar polar molecules are molecules are attracted to attracted to one another.one another.

8.4

8.4Attractions Between Attractions Between MoleculesMolecules

•Dispersion forcesDispersion forces, the , the weakest of all molecular weakest of all molecular interactions, are caused by interactions, are caused by the motion of electrons.the motion of electrons.– The strength of dispersion forces The strength of dispersion forces

generally increases as the generally increases as the number of electrons in a number of electrons in a molecule increases.molecule increases.


•Hydrogen BondsHydrogen Bonds–Hydrogen bondsHydrogen bonds are attractive are attractive forces in which a hydrogen forces in which a hydrogen covalently bonded to a very covalently bonded to a very electronegative atom is also weakly electronegative atom is also weakly bonded to an unshared electron pair bonded to an unshared electron pair of another electronegative atom.of another electronegative atom.

8.4

•Hydrogen Hydrogen bonding bonding among among water water moleculesmolecules


•The relatively The relatively strong attractive strong attractive forces between forces between water molecules water molecules cause the water cause the water to form small to form small drops on a waxy drops on a waxy surface.surface.

8.4

8.4Intermolecular Attractions Intermolecular Attractions and Molecular Propertiesand Molecular Properties

•Network solidsNetwork solids (or network (or network crystals) are solids in which all crystals) are solids in which all of the atoms are covalently of the atoms are covalently bonded to each other. bonded to each other.

•Network solids consist of molecules Network solids consist of molecules that do not melt until the that do not melt until the temperature reaches 1000°C or temperature reaches 1000°C or higher, or they decompose without higher, or they decompose without melting at all.melting at all.

8.4

•Diamond is Diamond is an example an example of a of a network network solid. solid. Diamond Diamond does not does not melt. It melt. It vaporizes vaporizes to a gas at to a gas at 3500°C or 3500°C or above.above.

Intermolecular Attractions Intermolecular Attractions and Molecular Propertiesand Molecular Properties

8.4

8.4 Section Quiz.8.4 Section Quiz.– 1.1. In a molecule, the atom with the largest In a molecule, the atom with the largest

electronegativity value electronegativity value

a) repels electrons more strongly and a) repels electrons more strongly and aquires a aquires a slightly negative charge.slightly negative charge.

b) repels electrons more strongly and b) repels electrons more strongly and aquires a aquires a slightly positive charge.slightly positive charge.

c) attracts electrons more strongly and c) attracts electrons more strongly and aquires a aquires a slightly positive charge.slightly positive charge.

d) attracts electrons more strongly and d) attracts electrons more strongly and aquires a aquires a slightly negative charge.slightly negative charge.

– 2.2. When polar molecules are placed When polar molecules are placed between oppositely charged plates, the between oppositely charged plates, the negative negative

a) molecules stick to the positive plates.a) molecules stick to the positive plates.

b) molecules stick to the negative plates.b) molecules stick to the negative plates.

c) ends of the molecules turn toward the c) ends of the molecules turn toward the positive plates.positive plates.

d) ends of the molecules turn toward the d) ends of the molecules turn toward the negative plates.negative plates.


–3.3. Which of the following Which of the following bond types is the weakest?bond types is the weakest?

a) ionic bonda) ionic bond

b) Van der Waals forceb) Van der Waals force

c) covalent bondc) covalent bond

d) hydrogen bondd) hydrogen bond


9.3 Naming and Writing 9.3 Naming and Writing Formulas for Molecular Formulas for Molecular

CompoundsCompounds

•A prefix in the name of a A prefix in the name of a binary molecular binary molecular compound tells how many compound tells how many atoms of an element are atoms of an element are present in each molecule present in each molecule of the compound.of the compound.

9.3 Naming Binary Naming Binary Molecular Molecular CompoundsCompounds

• Some guidelines for naming binary Some guidelines for naming binary molecular compounds:molecular compounds:

•Name the elements in the Name the elements in the order listed in the formula.order listed in the formula.

•Use prefixes to indicate the Use prefixes to indicate the number of each kind of number of each kind of atom.atom.

9.3Naming Binary Molecular Naming Binary Molecular CompoundsCompounds

•Omit the prefix Omit the prefix mono-mono- when when the formula contains only one the formula contains only one atom of the first element in atom of the first element in the name.the name.

•The suffix of the name of the The suffix of the name of the second element is -second element is -ideide..

9.3

Naming Binary Molecular Naming Binary Molecular CompoundsCompounds

Practice Traditional NamingPractice Traditional Naming•PFPF55

•XeFXeF44

•CClCCl44

•SFSF44

•NONO

•ClFClF33

Naming Binary Molecular Naming Binary Molecular CompoundsCompounds

•1) BF1) BF33

•2) NO2) NO

•3) N3) N22OO55

•4) CCl4) CCl44

•5) NO5) NO22

•6) I6) I22OO77

•7) CO7) CO22

•8) CF8) CF44

•9) NH9) NH33

•10) PCl10) PCl33

–Use the prefixes in the Use the prefixes in the name to tell you the name to tell you the subscript of each element subscript of each element in the formula. Then in the formula. Then write the correct symbols write the correct symbols for the two elements with for the two elements with the appropriate the appropriate subscripts.subscripts.

9.3 Writing Formulas for BinaryWriting Formulas for BinaryMolecular CompoundsMolecular Compounds

Writing FormulasWriting Formulas•dihydrogen dihydrogen

monoxidemonoxide

•phosphorus phosphorus pentachloridepentachloride

•sulfur dioxidesulfur dioxide

•carbon carbon dioxidedioxide

•dinitrogen dinitrogen pentoxidepentoxide

•sulfur sulfur hexafluoridehexafluoride

Write Formulas for:Write Formulas for:

•1) sulfur trioxide1) sulfur trioxide

•2) dinitrogen monoxide2) dinitrogen monoxide

•3) phosphorus pentachloride3) phosphorus pentachloride

•4) oxygen difluoride4) oxygen difluoride

•5) chlorine monoxide5) chlorine monoxide

9.3 Section Quiz.9.3 Section Quiz.– 1.1. Which of the following Which of the following

compounds is named INCORRECTLY?compounds is named INCORRECTLY?

a) CSa) CS22, carbon disulfide, carbon disulfide

b) BClb) BCl33, boron trichloride, boron trichloride

c) IFc) IF77, iodine heptafluoride, iodine heptafluoride

d) PCld) PCl55, phosphorus hexachloride, phosphorus hexachloride

– 2.2. Which of the following Which of the following molecular compounds is named molecular compounds is named INCORRECTLY?INCORRECTLY?

a) SbCla) SbCl33, antimony trichloride, antimony trichloride

b) Cb) C22OO55, dicarbon pentoxide, dicarbon pentoxide

c) CFc) CF44, carbon tetrafluoride, carbon tetrafluoride

d) Hd) H33As, hydrogen arsenideAs, hydrogen arsenide


– 3.3. The correct formula for The correct formula for tetraphosphorus trisulfide istetraphosphorus trisulfide is

a) Pa) P33SS44

b) Sb) S33PP44

c) Pc) P44SS33

d) Sd) S44PP33


9.4 Naming and Writing 9.4 Naming and Writing Formulas for Acids and Formulas for Acids and

BasesBases

•An An acidacid is a compound that is a compound that contains one or more hydrogen contains one or more hydrogen atoms and produces hydrogen atoms and produces hydrogen ions (Hions (H++) when dissolved in ) when dissolved in water. Acids have various uses.water. Acids have various uses.

9.4

Naming AcidsNaming Acids

•Three rules can help you name Three rules can help you name an acid with the general formula an acid with the general formula HHnnX.X.

–When the name of the anion When the name of the anion (X) ends in (X) ends in -ide,-ide, the acid name the acid name begins with the prefix begins with the prefix hydro-.hydro-. The stem of the anion has the The stem of the anion has the suffix suffix -ic-ic and is followed by the and is followed by the word word acidacid..

9.4



–When the anion name ends When the anion name ends in -in -iteite, the acid name is the , the acid name is the stem of the anion with the stem of the anion with the suffix -suffix -ousous, followed by the , followed by the word word acidacid..

9.4

–When the anion name ends When the anion name ends in in -ate,-ate, the acid name is the the acid name is the stem of the anion with the stem of the anion with the suffix suffix -ic-ic followed by the followed by the word word acidacid..

9.4


•A Summary of the Three A Summary of the Three Rules for Naming Acids.Rules for Naming Acids.

9.4


Name the acids:Name the acids:

•1) HF1) HF 7) HI7) HI

•2) HNO2) HNO33 8) HClO8) HClO22

•3) HC3) HC22HH33OO22 9) H9) H22SOSO44

•4) HBr4) HBr 10) H10) H22SS

•5) HClO5) HClO44

•6) HClO6) HClO33

•Use the rules for writing the Use the rules for writing the names of acids in reverse to names of acids in reverse to write the formulas for acids.write the formulas for acids.– What is the formula for hydrobromic What is the formula for hydrobromic

acid? Following Rule 1, hydrobromic acid? Following Rule 1, hydrobromic acid (acid (hydrohydro- prefix and -- prefix and -icic suffix) must suffix) must be a combination of hydrogen ion (Hbe a combination of hydrogen ion (H++) ) and bromide ion (Brand bromide ion (Br––). The formula of ). The formula of hydrobromic acid is HBr.hydrobromic acid is HBr.

9.4

Writing Formulas for AcidsWriting Formulas for Acids

Write formulas for:Write formulas for:

•1) sulfuric acid1) sulfuric acid

•2) sulfurous acid2) sulfurous acid

•3) hydrosulfuric acid3) hydrosulfuric acid

•4) hydroiodic acid4) hydroiodic acid

•5) nitric acid5) nitric acid

•6) carbonic acid6) carbonic acid

•Bases are named in the same way as Bases are named in the same way as other ionic compounds—the name of other ionic compounds—the name of the cation is followed by the name of the cation is followed by the name of the anion.the anion.

– For example, aluminum hydroxide consists For example, aluminum hydroxide consists of the aluminum cation (Alof the aluminum cation (Al3+3+) and the ) and the hydroxide anion (OHhydroxide anion (OH––). The formula for ). The formula for aluminum hydroxide is Al(OH)aluminum hydroxide is Al(OH)33..

9.4

Names and Formulas for Names and Formulas for BasesBases

9.4 Section Quiz9.4 Section Quiz– 1.1. The name for HThe name for H22S(aq) is S(aq) is

a) sulfuric acid.a) sulfuric acid.

b) hydrosulfuric acid.b) hydrosulfuric acid.

c) sulfurous acid.c) sulfurous acid.

d) hydrosulfurous acid.d) hydrosulfurous acid.

– 2.2. The chemical formula for The chemical formula for chlorous acid is chlorous acid is

a) HClOa) HClO22..

b) HClOb) HClO33..

c) HClOc) HClO44..

d) HCl.d) HCl.


– 3.3. The correct chemical name The correct chemical name for NHfor NH44OH is OH is

•nitrogen tetrahydrogen nitrogen tetrahydrogen hydroxide.hydroxide.

•nitrogen pentahydrogen nitrogen pentahydrogen oxide.oxide.

•ammonium oxyhydride.ammonium oxyhydride.

•ammonium hydroxide.ammonium hydroxide.


9.5 The Laws Governing 9.5 The Laws Governing Formulas and NamesFormulas and Names

–The Law of Definite ProportionsThe Law of Definite Proportions

•The The law of definite law of definite proportionsproportions states that in states that in samples of any chemical samples of any chemical compound, the masses of the compound, the masses of the elements are always in the elements are always in the same proportions.same proportions.

9.5

–The Law of Multiple ProportionsThe Law of Multiple Proportions

•The The law of multiple proportionslaw of multiple proportions: : Whenever the same two elements Whenever the same two elements form more than one compound, the form more than one compound, the different masses of one element that different masses of one element that combine with the same mass of the combine with the same mass of the other element are in the ratio of small other element are in the ratio of small whole numbers.whole numbers.

9.5

9.19.1

Mixed NamingMixed Naming

•1) FeBr1) FeBr33

•2) PCl2) PCl33

•3) NaHCO3) NaHCO33

•4) BaSO4) BaSO44

•5) BrF5) BrF55

•6) NaBr6) NaBr

•7) KClO7) KClO

•8) MgI8) MgI22

•9) Fe(OH)9) Fe(OH)22

•10) Zn10) Zn33(PO(PO44))22

Formula ReviewFormula Review

•1) potassium hydroxide1) potassium hydroxide

•2) sodium carbonate2) sodium carbonate

•3) nitric acid3) nitric acid

•4) cobalt (III) nitrate4) cobalt (III) nitrate

•5) calcium chloride5) calcium chloride

Write formulas for:Write formulas for:

•1) magnesium bromide1) magnesium bromide

•2) hydrochloric acid2) hydrochloric acid

•3) carbon disulfide3) carbon disulfide

•4) nickel (II) perchlorate4) nickel (II) perchlorate

•5) cesium fluoride5) cesium fluoride

Section Quiz 9.5.Section Quiz 9.5.– 1.1. The law of definite proportions states The law of definite proportions states

that in samples of any chemical that in samples of any chemical compound, the elements are always in compound, the elements are always in the same proportion by the same proportion by

a.a.mass.mass.

b.b.volume.volume.

c.c.group number.group number.

d.d.period number.period number.

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Chapter 8: Covalent Bonding 8.1 Molecular Compounds