Chapter 5

Chapter 5Chapter 5Molecules and Molecules and CompoundsCompounds

HomeworkHomework Assigned Problems (odd numbers only)Assigned Problems (odd numbers only)

RequiredRequired ““Problems” 23-79 (odd)Problems” 23-79 (odd)

““Cumulative Problems” 81-97 (odd)Cumulative Problems” 81-97 (odd)

Highlight ProblemsHighlight Problems ““Highlight Problems” 99, 101 (odd)Highlight Problems” 99, 101 (odd)

Compounds Display Constant CompositionCompounds Display Constant Composition

Compounds are pure substances consisting of Compounds are pure substances consisting of two or more elements held together by a two or more elements held together by a chemical bond chemical bond

A compound can be broken into its elements by A compound can be broken into its elements by a chemical processa chemical process

The percentage of each element in a specific The percentage of each element in a specific compound does not varycompound does not vary The Law of Definite Proportions The Law of Definite Proportions (Constant (Constant

Composition): In a pure compound, the elements are Composition): In a pure compound, the elements are always present in the same definite proportions by always present in the same definite proportions by massmass

Compounds Display Constant CompositionCompounds Display Constant Composition

Example:Example: Two samples of ammonia gas with different sample Two samples of ammonia gas with different sample

massesmasses Upon decomposition, the mass ratios of nitrogen to Upon decomposition, the mass ratios of nitrogen to

hydrogen are the samehydrogen are the same

Sample 1: Sample 2:4.63g 0.327

g5131

.4.62

g 0.356

g6441

.

Chemical Formulas: Chemical Formulas: How to Represent CompoundsHow to Represent Compounds

Chemical formulas are a concise way of stating Chemical formulas are a concise way of stating a specific chemical compound’s compositiona specific chemical compound’s composition

The notation contains the symbols of the The notation contains the symbols of the elements present and the subscripts to indicate elements present and the subscripts to indicate the number of atoms per element in a structural the number of atoms per element in a structural unit of the compoundunit of the compound

Aspirin’s chemical formula is C9H8O4

Element symbols

21 atoms are present:9 carbon atoms, 8 hydrogen atoms, and 4 oxygen atomsRatio of C to H to O is 9:8:4

subscripts


All pure samples of a compound have the same All pure samples of a compound have the same compositioncomposition

If only one atom is present in a molecule, the If only one atom is present in a molecule, the subscript “1” is omittedsubscript “1” is omitted

Follow the capitalization rules for elemental Follow the capitalization rules for elemental symbolssymbols

When writing formulas, list the metal or most When writing formulas, list the metal or most metallic element firstmetallic element first

Co is the symbol for cobaltCO is the formula for carbon monoxide

sodium chloride NaCl not ClNacarbon dioxide CO2 not O2C


If a chemical formula contains groups of atoms in parentheses, the subscript following the parentheses indicates the number polyatomic units in the formula

Number of atoms is determined by multiplying the subscript outside the parenthesis by the subscript for every atom inside the parenthesis

Composition is 1 Mg atom, 2 N atoms, 6 O atoms

Polyatomic ion

A Molecular View ofA Molecular View ofElements and CompoundsElements and Compounds

Pure substancesPure substances ElementsElements

AtomicAtomic MolecularMolecular

CompoundsCompounds Ionic Ionic MolecularMolecular

Elements and CompoundsElements and Compounds Elements are substances that cannot be decomposed into simpler Elements are substances that cannot be decomposed into simpler

substancessubstances Each element is composed of only one type of atomEach element is composed of only one type of atom Most elements are Most elements are atomicatomic elements elements and exist as single atoms and exist as single atoms

(monatomic) (monatomic) Molecular elements Molecular elements are found naturally as two or more of the same are found naturally as two or more of the same

type of atom bound together (diatomic)type of atom bound together (diatomic)

Elements and CompoundsElements and Compounds

A compound can be decomposed into two or more simpler A compound can be decomposed into two or more simpler substancessubstances

The ultimate breakdown products are elementsThe ultimate breakdown products are elements Two types of compoundsTwo types of compounds

MolecularMolecular IonicIonic

Molecular CompoundsMolecular Compounds

A molecule is a group of two or more atoms A molecule is a group of two or more atoms bound together as a unitbound together as a unit

A A molecular compound molecular compound involves a bond between involves a bond between two or more nonmetalstwo or more nonmetals

Bonds occur between different or identical Bonds occur between different or identical atomsatoms

The individual molecule is the smallest particle The individual molecule is the smallest particle that can exist as a stable, independent unit of that can exist as a stable, independent unit of the compoundthe compound

Molecular (Covalent) CompoundsMolecular (Covalent) Compounds Molecular compounds are compounds composed of Molecular compounds are compounds composed of

molecules that exist as the individual structural unit molecules that exist as the individual structural unit The simplest molecule contains two atoms (diatomic). The simplest molecule contains two atoms (diatomic).

They can be the same or different atomsThey can be the same or different atoms Next in complexity are triatomic and tetraatomicNext in complexity are triatomic and tetraatomic

COcarbon monooxide

H2Owater

A diatomic molecule A triatomic molecule

O2

oxygen

A diatomic molecule

O3

ozone

A triatomic molecule

Ionic CompoundsIonic Compounds

Ionic compounds Ionic compounds are care compounds which ompounds which are held together by the attraction of are held together by the attraction of positive and negative ionspositive and negative ions

Solid crystalsSolid crystals formed by a very ordered formed by a very ordered packing of oppositely charged ionspacking of oppositely charged ions

Most ionic compounds are composed of a Most ionic compounds are composed of a metal and a nonmetalmetal and a nonmetal

High melting temperaturesHigh melting temperatures

Fig4_21a

Cl–

Cl–

Cl–

Cl–

Cl–

Cl–

Na+

Na+

Na+

Na+

Na+

Na+

Ionic CompoundsIonic Compounds SolidsSolids They do not exist as single They do not exist as single

moleculesmolecules The chemical formula The chemical formula

represents the simplest ratio represents the simplest ratio that these atoms combine that these atoms combine togethertogether

Held strongly together, these Held strongly together, these ions are packed together into a ions are packed together into a “lattice” “lattice”

Each NaEach Na++ ion is surrounded on ion is surrounded on each side by Cleach side by Cl-- ions ions

Each ClEach Cl-- ion is surrounded on ion is surrounded on each side by Naeach side by Na++ ions ions

Formula unit = NaCl

Ionic CompoundsIonic Compoundsvs. Molecular Compoundsvs. Molecular Compounds

For molecular For molecular compounds, the compounds, the chemical formulas chemical formulas give the composition give the composition of the moleculesof the molecules

For ionic compounds, For ionic compounds, the chemical formulas the chemical formulas give the ion ratio give the ion ratio within the compoundwithin the compound

Writing Formulas for Ionic Compounds Writing Formulas for Ionic Compounds (Charge Balance in Ionic Compounds)(Charge Balance in Ionic Compounds)

Binary ionic compounds are composed of Binary ionic compounds are composed of only two elements (metal and nonmetal)only two elements (metal and nonmetal) The symbol of the cation always The symbol of the cation always

precedes the symbol of the anionprecedes the symbol of the anion The sum of the positive charges (cation) The sum of the positive charges (cation)

must equal the sum of the negative must equal the sum of the negative charges (anion) charges (anion)

Net charge is zero (charge-neutral)Net charge is zero (charge-neutral) Subscripts written as whole numbers Subscripts written as whole numbers

indicate the number of each ion in the indicate the number of each ion in the formula unitformula unit

Writing Formulas for Ionic Compounds Writing Formulas for Ionic Compounds Subscripts in FormulasSubscripts in Formulas

Sodium ChlorideSodium Chloride Formed from Formed from

sodium and sodium and chlorine atomschlorine atoms

An ionic bond An ionic bond forms consisting of forms consisting of a sodium ion a sodium ion (+ charge) and a (+ charge) and a chloride ion chloride ion (- charge)(- charge)

Each sodium loses Each sodium loses one electron to one electron to achieve an octet achieve an octet

Each chlorine atom Each chlorine atom gains one electron gains one electron to achieve an octetto achieve an octet

Formula is Formula is NaClNaCl

Writing Formulas for Ionic Compounds Writing Formulas for Ionic Compounds Subscripts in FormulasSubscripts in Formulas

Magnesium ChlorideMagnesium Chloride Formed from Formed from

magnesium and magnesium and two chlorinestwo chlorines

An ionic bond An ionic bond forms consisting of forms consisting of a magnesium ion a magnesium ion (2+ charge) and (2+ charge) and two chloride ions two chloride ions (- charge (- charge each)each)

Each magnesium Each magnesium loses two electrons loses two electrons to achieve an octet to achieve an octet

Each chlorine atom Each chlorine atom gains one electron to gains one electron to achieve an octetachieve an octet

Formula is Formula is MgClMgCl22

Writing Ionic Formulas for Writing Ionic Formulas for Ionic ChargesIonic Charges

Subscripts in a formula represent the number of positive and Subscripts in a formula represent the number of positive and negative ionsnegative ions Write the formula for the ionic compound containing NaWrite the formula for the ionic compound containing Na+ + and Nand N3-3-

••

••

• •

• •

• •

• •

Na•

Na•

N

Na+

Na+

Na+

N • • •

• •

• •

• •

• • • •

3-

Net charge: 3(1+) + 1(3-)=0Net charge: 3(1+) + 1(3-)=0Formula:Formula: NaNa33NN

Na•

Each loses 1eEach loses 1e--

Gains 3eGains 3e--

Naming Ionic CompoundsNaming Ionic Compounds

For ionic compounds containing two elements:For ionic compounds containing two elements: Compounds containing a metal and a Compounds containing a metal and a

nonmetal are called nonmetal are called binary ionic compoundsbinary ionic compounds Two types of metals:Two types of metals:

Single Cation Metals: Form one positive ionSingle Cation Metals: Form one positive ion Multiple Cation Metals: Form more than one Multiple Cation Metals: Form more than one

positive ionpositive ion

The systematic naming uses the name of the The systematic naming uses the name of the cation first, followed by the name of the anioncation first, followed by the name of the anion

Subscripts in the formula are not included in Subscripts in the formula are not included in the namethe name

Types of Metal IonsTypes of Metal Ions

Single Cation Metals (Type I)Single Cation Metals (Type I) Form only one type of ion (one possible Form only one type of ion (one possible

charge)charge) Main group metals in groups IA, IIA, and Main group metals in groups IA, IIA, and

some IIIAsome IIIA e.g. Sodium only forms one ion e.g. Sodium only forms one ion (Na(Na++)) in in

chemical reactionschemical reactions Determine charge by position on the Determine charge by position on the

periodic tableperiodic table (also see table 5.3 on page (also see table 5.3 on page 136)136)

Types of Metal IonsTypes of Metal Ions

Single Cation Metals (Type I)Single Cation Metals (Type I) Form only one type of ion (one possible charge)Form only one type of ion (one possible charge) Main group metals in groups IA, IIA, and some IIIAMain group metals in groups IA, IIA, and some IIIA e.g. Sodium only forms one ion e.g. Sodium only forms one ion (Na(Na++)) in chemical in chemical

reactionsreactions Determine charge by position on the Determine charge by position on the periodic tableperiodic table

(also see table 5.3 on page 136)(also see table 5.3 on page 136)

Types of Metal IonsTypes of Metal Ions Multiple Cation Metals (Type II) Multiple Cation Metals (Type II)

Form two or more types of ions (variable Form two or more types of ions (variable possible charge)possible charge)

Transition metals in groups 3B to 12B, and Transition metals in groups 3B to 12B, and some 4A and 5Asome 4A and 5A

For example, iron forms two ions (FeFor example, iron forms two ions (Fe2+ 2+ and and FeFe3+3+) in chemical reactions) in chemical reactions

Determine charge by the “stock system” for Determine charge by the “stock system” for naming ions naming ions

The The metal namemetal name followed by a followed by a Roman Roman numeralnumeral in parentheses to indicate its in parentheses to indicate its charge (see table 5.4 on page 136)charge (see table 5.4 on page 136)

Types of Metal IonsTypes of Metal Ions Multiple Cation Metals (Type II) Multiple Cation Metals (Type II)

Form two or more types of ions (variable possible charge)Form two or more types of ions (variable possible charge) Transition metals in groups 3B to 12B, and some 4A and 5ATransition metals in groups 3B to 12B, and some 4A and 5A For example, iron forms two ions (FeFor example, iron forms two ions (Fe2+ 2+ and Feand Fe3+3+) in chemical ) in chemical

reactionsreactions Determine charge by the “stock system” for naming ions Determine charge by the “stock system” for naming ions The The metal namemetal name followed by a followed by a Roman numeralRoman numeral in parentheses to in parentheses to

indicate its charge (see table 5.4 on page 136)indicate its charge (see table 5.4 on page 136)

Naming Type I Binary Ionic CompoundsNaming Type I Binary Ionic Compounds

Compounds which contain a positively Compounds which contain a positively charged metallic ion and a negatively charged charged metallic ion and a negatively charged nonmetallic ionnonmetallic ion

Name metal Name metal cationcation first, name nonmetal first, name nonmetal anionanion secondsecond

Single metal cation name is the Single metal cation name is the metal name metal name only, only, drop the word “ion”drop the word “ion”

Nonmetal anion named by changing the Nonmetal anion named by changing the ending on the nonmetal name to -ending on the nonmetal name to -ideide

Name of metal__base name of nonmetal + -ide

Naming Type I Ionic CompoundsNaming Type I Ionic Compounds

NaINaI Sodium IodSodium Iodideide

CaFCaF22

Calcium FluorCalcium Fluorideide LiLi22OO

Lithium OxLithium Oxideide AgClAgCl

Silver ChlorSilver Chlorideide

KClPotassium Chloride

Na3PSodium Phosphide

Rb2SRubidium Sulfide

Mg3N2

Magnesium Nitride

Naming Type II Binary Ionic CompoundsNaming Type II Binary Ionic CompoundsMultiple Cation Metal CompoundsMultiple Cation Metal Compounds

Metal listed first in formula & name (same Metal listed first in formula & name (same order as for Type I compounds)order as for Type I compounds)

Determine metal cation charge from the Determine metal cation charge from the anion chargeanion charge

Common multiple cations in Table 5.4, Common multiple cations in Table 5.4, page 136page 136

Naming Type II Binary Ionic CompoundsNaming Type II Binary Ionic CompoundsMultiple Cation Metal CompoundsMultiple Cation Metal Compounds

Use the Use the metal namemetal name (cation) first, followed (cation) first, followed by a by a Roman numeralRoman numeral in parentheses to in parentheses to indicate its chargeindicate its charge

Nonmetal anion named by changing the Nonmetal anion named by changing the ending on the nonmetal name to -ending on the nonmetal name to -ideide

Name of metal (charge of metal)______base name of nonmetal + -idecation anion

Naming Type II Binary Ionic CompoundsNaming Type II Binary Ionic Compounds

FeIFeI33

1(1(??)+3(-1)=0)+3(-1)=0 Iron Iron (III)(III) Iod Iodideide

CuCu22OO 2(2(??)+1(-2)=0)+1(-2)=0 Copper Copper (I)(I) Ox Oxideide

SnBrSnBr22

1(1(??)+2(-1)=0)+2(-1)=0 Tin Tin (II)(II) Brom Bromideide

Naming Type II Binary Ionic CompoundsNaming Type II Binary Ionic Compounds Determining the Charge of the Cation from the AnionDetermining the Charge of the Cation from the Anion

Determine the charge of Cu in CuDetermine the charge of Cu in Cu22OOWrite the name of the compoundWrite the name of the compound1)1)Determine theDetermine the charge of the cation from charge of the cation from

the anionthe anion CuCu22O - the nonmetal anion is O, since it is O - the nonmetal anion is O, since it is

in Group 6A, its charge is in Group 6A, its charge is 2-2- Since there are 2 Cu ions in the formula Since there are 2 Cu ions in the formula

and the total positive charge is and the total positive charge is 2+2+, divide , divide by the by the number of cationsnumber of cations so each Cu has so each Cu has a a 1+1+ charge charge


2)2) Name the cation by its element name and Name the cation by its element name and use a Roman numeral in parenthesis to use a Roman numeral in parenthesis to indicate its chargeindicate its charge

Copper (I)Copper (I)3)3) Name the anion by changing the last part of Name the anion by changing the last part of

its element name to –its element name to –ideide OxygenOxygen4)4) Write the name of the cation first and the Write the name of the cation first and the

name of the anion secondname of the anion second

copper (I) oxide

oxide


• SnISnI44

• 1(?)+4(-1)=01(?)+4(-1)=0• Tin Tin (IV)(IV) iod iodideide

• HgOHgO• 1(?)+1(-2)=01(?)+1(-2)=0• Mercury Mercury (II)(II) Ox Oxideide

• MnClMnCl22• 1(?)+2(-1)=01(?)+2(-1)=0• Manganese Manganese (II) (II) ChlorChlorideide

Writing Formulas from the Name of Writing Formulas from the Name of an Ionic Compoundan Ionic Compound

Usually involves a metal and a nonmetalUsually involves a metal and a nonmetal

1)1) Identify the cation and the anionIdentify the cation and the anion

2)2) Balance the charges to write the formulaBalance the charges to write the formula If it is a multiple cation metal, the Roman If it is a multiple cation metal, the Roman

numeral determines the charge of the numeral determines the charge of the cationcation

3)3) When writing the formula, take the name of When writing the formula, take the name of the cation first, followed by the name of the the cation first, followed by the name of the anionanion


Compound name is lithium chlorideCompound name is lithium chloride LiLi++ and Cl and Cl-- are the ions are the ions Balance the chargesBalance the charges

Write the formulaWrite the formula LiClLiCl is the formula using the is the formula using the

subscripts from the charge balancesubscripts from the charge balance

0 )(1)(1

ClLi

11


Compound name is iron (III) oxideCompound name is iron (III) oxide FeFe3+3+ and O and O2-2- are the ions are the ions Balance the chargesBalance the charges

Write the formulaWrite the formula FeFe22OO33 is the formula using the is the formula using the


0 )(2)(3

OFe 23

2 3

Polyatomic IonsPolyatomic Ions Polyatomic ionsPolyatomic ions are a group of atoms are a group of atoms

covalently bonded together into a single unit covalently bonded together into a single unit The unit obtains a chargeThe unit obtains a charge Most PA ions are negatively charged Most PA ions are negatively charged

Oxyanions (anions): P, S, C, or N Oxyanions (anions): P, S, C, or N covalently bound to one or more oxygenscovalently bound to one or more oxygens

Never occur independently, always Never occur independently, always associated with ions of opposite chargeassociated with ions of opposite charge

Only one PA is positively chargedOnly one PA is positively charged ammonium ionammonium ion

Naming Ionic Compounds Containing a Naming Ionic Compounds Containing a Polyatomic IonPolyatomic Ion

Must Must memorizememorize name, formula and name, formula and charge (charge (Table 5.6 on page 138Table 5.6 on page 138). Look for ). Look for relationships between ionsrelationships between ions

Most PA ions areMost PA ions are oxyanions oxyanions: The number : The number of oxygen atoms bonded to the same of oxygen atoms bonded to the same element (e.g. P, S, or N) will determine element (e.g. P, S, or N) will determine the name (suffix) of the ionthe name (suffix) of the ion ~~ateate is most common is most common ~~iteite has one less oxygen bonded has one less oxygen bonded

Naming Ionic Compounds Containing a Naming Ionic Compounds Containing a Polyatomic IonPolyatomic Ion ~~ate, ate, ~~ite pairs of ionsite pairs of ions

The ion in the pair with the most oxygens is always the The ion in the pair with the most oxygens is always the ~~ate ionate ion

The ion in the pair with one less oxygen is always The ion in the pair with one less oxygen is always the the ~~ite ion ite ion

Ion pair with a 3- charge Ion pair with a 3- charge phosphphosphateate (PO (PO44

3-3-), phosph), phosphiteite (PO (PO333-3-))

Ion pair with a 2- charge Ion pair with a 2- charge sulfsulfateate (SO (SO44

2-2-), sulf), sulfiteite (SO (SO332-2-) )

Ion pair with a 1- chargeIon pair with a 1- charge nitrnitrateate (NO (NO33

--), nitr), nitriteite (NO (NO22--))

Naming Ionic Compounds Containing a Polyatomic IonNaming Ionic Compounds Containing a Polyatomic Ion

Group 7A elementsGroup 7A elements can form more than two can form more than two types of polyatomic ions (oxyanions)types of polyatomic ions (oxyanions)

Additional prefixes are used to differentiate Additional prefixes are used to differentiate the ionsthe ions

See page 138-9 (class text) and page 330 See page 138-9 (class text) and page 330 (lab text)(lab text)

The number of oxygens attached to the The number of oxygens attached to the central atom has an effect on the name of central atom has an effect on the name of the ionthe ion

e.g. Polyatomic ions of chlorine, bromine e.g. Polyatomic ions of chlorine, bromine and iodineand iodine

Naming Ionic Compounds Containing a Naming Ionic Compounds Containing a Polyatomic Ion (Group VIIA)Polyatomic Ion (Group VIIA)

Example: Polyatomic ions of chlorineExample: Polyatomic ions of chlorine

1)1) -ate ion-ate ion chlorchlorate ate = ClO= ClO33

--

2)2) -chlorate ion with 1 more O than -chlorate ion with 1 more O than chloratechlorate, use , use per-per- prefixprefix perperchlorate = ClOchlorate = ClO44

--

3)3) - - chloratechlorate ion with 1 less O, use ion with 1 less O, use -ite-ite suffix suffix chlorchloriteite = ClO = ClO22

--

4)4) --chloritechlorite ion with 1 less O, use ion with 1 less O, use hypo-hypo- prefix prefix hypohypochlorite = ClOchlorite = ClO--


Named the same way as binary ionic Named the same way as binary ionic compoundscompounds

Positive ion (metal) name is written firstPositive ion (metal) name is written first Polyatomic ions name follows the metalPolyatomic ions name follows the metal No prefixes are used in the nameNo prefixes are used in the name Cation: Check to see if metal is single or Cation: Check to see if metal is single or

multiple cationmultiple cation Use the name of the PA ion given in table Use the name of the PA ion given in table

5.6 on page 1385.6 on page 138


• CaSOCaSO44

• calcium sulfatecalcium sulfate• CaCa2+ 2+ and SOand SO44

2-2-

• LiLi22COCO33

• lithium carbonatelithium carbonate• LiLi++, CO, CO33

2-2-

• Al(NOAl(NO33))33

• aluminum nitratealuminum nitrate• AlAl3+3+, NO, NO33

--

Writing Formulas for Compounds Writing Formulas for Compounds Containing a Polyatomic IonContaining a Polyatomic Ion

Formulas are written like binary ionic Formulas are written like binary ionic compoundscompounds

Consider polyatomic ions as single units with Consider polyatomic ions as single units with a certain chargea certain charge

Obtain the correct ratio of cation to anion to Obtain the correct ratio of cation to anion to achieve a achieve a net charge of zeronet charge of zero

Use parentheses if more than one of the Use parentheses if more than one of the same PA unit is needed in a formulasame PA unit is needed in a formula

Use subscripts to indicate the number of a Use subscripts to indicate the number of a particular ion in a formulaparticular ion in a formula


Compound name is magnesium carbonateCompound name is magnesium carbonate MgMg2+2+ and CO and CO33

2-2- are the ions are the ions Balance the chargesBalance the charges

Write the formulaWrite the formula

MgCOMgCO33 is the formula using the is the formula using the


0 )(2)(2

COMg 23

2

1 1


Compound name is calcium nitrateCompound name is calcium nitrate CaCa2+2+ and NO and NO33

-- are the ions are the ions Balance the chargesBalance the charges


Ca(NOCa(NO33))22 is the formula using the is the formula using the


0 )(1)(2

NOCa 32

1 2


Compound name is iron (III) sulfateCompound name is iron (III) sulfate FeFe3+3+ and SO and SO44

2-2- are the ions are the ions Balance the chargesBalance the charges


FeFe22(SO(SO44))33 is the formula using the is the formula using the


0 )(2 )(3

SOFe 24

3

2 3


Compound name is ammonium phosphateCompound name is ammonium phosphate NHNH44

++ and PO and PO443-3- are the ions are the ions

Balance the chargesBalance the charges


(NH(NH44))33POPO44 is the formula using the is the formula using the


0 )(3 )(1

PONH 34

4

3 1

Naming Molecular CompoundsNaming Molecular Compounds

Molecular binary compounds Molecular binary compounds Composed of two nonmetal elementsComposed of two nonmetal elements

Naming a compoundNaming a compound Use the full (element ) name for the first Use the full (element ) name for the first

nonmetalnonmetal Add the Add the –ide–ide ending to the full name of the ending to the full name of the

second nonmetalsecond nonmetal Second nonmetal named like the nonmetal in Second nonmetal named like the nonmetal in

binary ionic compounds (anion) binary ionic compounds (anion) Indicate the number of atoms by adding Indicate the number of atoms by adding

numerical prefixesnumerical prefixes

Prefixes Used in Naming Molecular (Covalent) Prefixes Used in Naming Molecular (Covalent) Compounds (page 140)Compounds (page 140)

SubscriptSubscript Prefix usedPrefix used

11 monomono~~ (Usually omitted on the first atom)(Usually omitted on the first atom)

22 di di ~~

33 tri tri ~~

44 tetra tetra ~~

55 penta penta ~~

66 hexa hexa ~~

77 hepta hepta ~~

88 octa octa ~~

99 nona nona ~~

1010 deca deca ~~


In ionic compounds the subscripts are not mentioned in In ionic compounds the subscripts are not mentioned in the namethe name

Many compounds can exist for many pairs of nonmetallic Many compounds can exist for many pairs of nonmetallic elements (e.g. nitrogen and oxygen)elements (e.g. nitrogen and oxygen)

ONNONO 22

BaCl2

barium chloride

barium dichloride

Na2SO4

sodium sulfate

disodium sulfate

nitrogen monoxide nitrogen dioxide dinitrogen monoxide

Prefix- Name of 1st nonmetal ___Prefix- Name of 2nd nonmetal + -ide

Naming Molecular CompoundsNaming Molecular Compounds IFIF55

iodine iodine pentapentafluorfluorideide

BB22OO33

didiboron boron tritrioxoxideide

NONO33

nitrogen nitrogen tritrioxoxideide


• AsClAsCl33• arsenic arsenic tritrichlorchlorideide

• COCO22

• carbon carbon didioxoxideide

• COCO• carbon carbon monmonoxoxideide

Naming Molecular (Covalent) Compounds Naming Molecular (Covalent) Compounds from their Chemical Formulafrom their Chemical Formula

When writing a formula from the When writing a formula from the namename of of a binary molecular compounda binary molecular compound

You must know (memorize) definition of You must know (memorize) definition of the numerical prefixes used in naming the numerical prefixes used in naming covalent compounds (see page 140) covalent compounds (see page 140)

1)1) Write the Write the symbolssymbols in order the in order the elements appear in the nameelements appear in the name

2)2) Identify the Identify the prefixesprefixes with the with the appropriate subscriptsappropriate subscripts

ExamplesExamples

• DiDinitrogen nitrogen PentPentoxideoxide• NN22OO55

• TetraTetraphosphorous phosphorous HexaHexasulfidesulfide• PP44NN66

• Iodine Iodine HeptaHeptasulfidesulfide• IFIF77

• MonoMonoiodine Heptasulfideiodine Heptasulfide

Naming Molecular Compounds A systematic name for a compound (IUPAC rules)

conveys information about the composition of the compound

Some compounds retain their “common” or “trivial” names which are not based upon IUPAC rules

These names were acquired before the systematic nomenclature was established

Naming Acids Naming Acids

Acids are hydrogen containing molecular Acids are hydrogen containing molecular compounds that produce Hcompounds that produce H+ + and an anion when and an anion when dissolved in waterdissolved in water

They have a sour taste and dissolve some They have a sour taste and dissolve some metalsmetals

They can be recognized by H written as the first They can be recognized by H written as the first element in their formulaselement in their formulas

Acids: HCl, H2S, H2SO4, HNO3

Nonacids: NH3, CH4, PH3, SiH4

Naming AcidsNaming Acids Many molecular compounds containing hydrogen Many molecular compounds containing hydrogen

dissolve in water to form Hdissolve in water to form H++ and an anion and an anion All acids produce HAll acids produce H++ ion which gives acids their ion which gives acids their

characteristic propertiescharacteristic properties The names of acids are derived from the names of The names of acids are derived from the names of

the anions produced by dissociation from the Hthe anions produced by dissociation from the H++ ion ion

Naming AcidsNaming Acids

Binary acidsBinary acids have a H have a H++ ion and a nonmetal ion and a nonmetal anionanion

OxyacidsOxyacids have a H have a H++ ion and a polyatomic ion and a polyatomic anion (PA ion contains oxygen)anion (PA ion contains oxygen)

There are three rules for naming acids There are three rules for naming acids depending on whether the name of the depending on whether the name of the anion has the suffixanion has the suffix - -ideide,-,-ateate, -, -iteite

Naming Binary Acids:Naming Binary Acids:

Anions Ending in -ideAnions Ending in -ide

Use the prefix Use the prefix hydro-hydro- before the base (root) before the base (root) name of the elementname of the element

Add the suffixAdd the suffix -ic-ic and the word and the word acidacid to the to the root name for the elementroot name for the element

Example: HClExample: HCl hydrohydrochlorchloricic acidacid

Example: HIExample: HI hydrohydroiodiodicic acidacid

Hydro- + base name of nonmetal + -ic______ acid

Naming OxyacidsNaming Oxyacids An oxyacid is a molecular compound composed An oxyacid is a molecular compound composed

of hydrogen, oxygen, and another nonmetalof hydrogen, oxygen, and another nonmetal Exist as pure compounds and water solutionsExist as pure compounds and water solutions Produce HProduce H++ and a polyatomic ion when and a polyatomic ion when

dissolved in waterdissolved in water

For many nonmetals there is a series of For many nonmetals there is a series of oxyacids and they differ only in the amount of oxyacids and they differ only in the amount of oxygen presentoxygen present

HClO4-, HClO3

-, HClO2-, HClO-

HNO3 H+ + NO3

-

SO42-, SO3

2- , NO3-, NO2

-

Naming OxyacidsNaming OxyacidsAnions Ending in -ateAnions Ending in -ate

A series of oxyanionsA series of oxyanions

Use the root name of the polyatomic ionUse the root name of the polyatomic ion If polyatomic ion ends in If polyatomic ion ends in –ate–ate, use , use –ic–ic suffix suffix

Example: HExample: H22SOSO44 (from SO (from SO442- 2- ,sulf,sulfateate ion) ion)

sulfursulfuric acid (NO hydro- prefix used)ic acid (NO hydro- prefix used)

base name of polyatomic ion + -ic______ acid

SO32-

sulfitesulfate

SO42-

Naming OxyacidsNaming OxyacidsAnions Ending in -iteAnions Ending in -ite

A series of oxyanionsA series of oxyanions

Use the root name of the polyatomic ionUse the root name of the polyatomic ion If polyatomic ion ends in If polyatomic ion ends in –ite–ite, use , use –ous–ous suffix suffix

Example: HExample: H22SOSO33 (from SO (from SO332- 2- ,sulf,sulfiteite ion) ion)

sulfursulfurous acid (NO hydro- prefix ous acid (NO hydro- prefix used)used)

base name of polyatomic ion + -ous______ acid

sulfate

SO42- SO3

2-

sulfite

Summary of Writing Ionic Summary of Writing Ionic CompoundsCompounds

Summary of guidelines when writing binary ionic Summary of guidelines when writing binary ionic compoundcompound

The symbol of the cation always precedes the The symbol of the cation always precedes the anionanion

The sum of the positive charges must equal the The sum of the positive charges must equal the sum of the negative charges:sum of the negative charges:A net charge of zeroA net charge of zero

Whole numbers are written as subscripts to Whole numbers are written as subscripts to indicate the number of each ion (or group) in the indicate the number of each ion (or group) in the formulaformula

Formula Mass: The Mass of a Molecule or Formula Unit

The formula mass is the sum of the atomic masses of atoms present in a single formula unit of a substance

It is obtained by adding the atomic masses of the constituent elements

Each atomic mass is counted as many times as the symbol occurs in the formulaCalculate the formula mass of Calcium NitrateChemical formula: Ca(NO3)2

Formula Mass = 1 (formula mass of Ca) + 2 (formula mass of N) + 6 (formula mass of O)

= 40.08 amu + 2 (14.01 amu) + 6 (16.00 amu) = 164.1 amu

Chapter 5

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