Introductory Chemistry, 2 nd Edition Nivaldo Tro Chapter 5 Molecules and Compounds.

Introductory ChemistryIntroductory Chemistry, 2, 2ndnd Edition EditionNivaldo TroNivaldo Tro

Chapter 5Molecules andCompounds

Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 22

Molecules and CompoundsMolecules and Compounds

CompoundsCompounds = composed of 2 or = composed of 2 or more elements chemically more elements chemically combinedcombined

Properties completely different Properties completely different from component elementsfrom component elements

SaltSalt– Sodium (Na)Sodium (Na) – shiny, reactive, – shiny, reactive,

poisonouspoisonous– Chlorine (Cl)Chlorine (Cl) – pale yellow – pale yellow

gas, reactive, poisonousgas, reactive, poisonous– Sodium chloride (NaCl)Sodium chloride (NaCl) – –

table salt, flavor enhancertable salt, flavor enhancer


Pure substancesPure substances have have constant compositionconstant composition– all samples of a all samples of a pure pure

substancesubstance contain same contain same elements in same ratios or elements in same ratios or proportions regardless of proportions regardless of sourcesource

– mixturesmixtures have variable have variable compositioncomposition

Law of Constant CompositionLaw of Constant Composition


Compounds Display Compounds Display Constant CompositionConstant Composition

Water (HWater (H22O)O) decomposed by electrolysis yields decomposed by electrolysis yields

16.0 grams of oxygen to every 2.00 grams of 16.0 grams of oxygen to every 2.00 grams of hydrogen. hydrogen.

Water has a Water has a constantconstant Mass RatioMass Ratio of Oxygen to of Oxygen to Hydrogen of 8.0.Hydrogen of 8.0.

0.8g 2.0

g 0.16

hydrogen of mass

oxygen of mass Ratio Mass


Formulas Describe CompoundsFormulas Describe Compounds

CompoundCompound = a distinct substance that is = a distinct substance that is composed of atoms of two or more elementscomposed of atoms of two or more elements

FormulasFormulas give the number and type of each give the number and type of each atom in the simplest unit of the compoundatom in the simplest unit of the compound

– Molecules (HMolecules (H22O)O) or or ions (CaClions (CaCl22))

Number of atoms of each element is written to Number of atoms of each element is written to the right of the element as a the right of the element as a subscriptsubscript– if only one atom, 1 subscript is not writtenif only one atom, 1 subscript is not written

Polyatomic groupsPolyatomic groups are placed in parentheses are placed in parentheses

– if more than one, i. e. Caif more than one, i. e. Ca(NO(NO33))22


Formulas Describe CompoundsFormulas Describe Compounds

Examples:Examples:

water = Hwater = H22O O two atoms of two atoms of

hydrogen and 1 atom of hydrogen and 1 atom of oxygenoxygen

table sugar (sucrose) = Ctable sugar (sucrose) = C1212HH2222OO1111

12 atoms of 12 atoms of CC, 22 atoms of H , 22 atoms of H

and 11 atoms and 11 atoms OO


Classifying MaterialsClassifying Materials

Atomic elementsAtomic elements = = elements whose particles elements whose particles are single atoms; Na, Ne, are single atoms; Na, Ne, Hg, AgHg, Ag

Molecular elementsMolecular elements = = elements whose particles elements whose particles are multi-atom molecules; are multi-atom molecules; HH22, O, O22, N, N22, Cl, Cl22

88

Molecular ElementsMolecular ElementsCertain elements occur as 2 atom moleculesCertain elements occur as 2 atom moleculesRule of 7’s Rule of 7’s – there are 7 common diatomic elementsthere are 7 common diatomic elements– find the element with atomic number 7, Nfind the element with atomic number 7, N– make a figure 7 by going over to Group 7A, then downmake a figure 7 by going over to Group 7A, then down– don’t forget to include Hdon’t forget to include H22

H2

Cl2

Br2

I2

VIIAVIIAN2 O2 F2

7


Classifying MaterialsClassifying Materials

Molecular compoundsMolecular compounds = = compounds whose particles compounds whose particles are molecules made of only are molecules made of only nonmetals, i.e. COnonmetals, i.e. CO22

Ionic compoundsIonic compounds = = compounds whose particles compounds whose particles are are cations (+)cations (+) and and anions (-)anions (-), , i.e. NaCli.e. NaCl


Molecular CompoundsMolecular Compounds

Two or more Two or more nonmetalsnonmetals, i.e. H, i.e. H22O, O,

COCO22, C, C66HH1212OO66

Smallest unit is a Smallest unit is a moleculemolecule


Order of Elements in a FormulaOrder of Elements in a FormulaMetals written firstMetals written first– NaClNaCl

Nonmetals written in order Nonmetals written in order from Table 5.1from Table 5.1– COCO22

– occasional exceptions for occasional exceptions for historical or informational historical or informational reasonsreasons

HH22O, but NaO, but NaOHOH

Order of Listing Order of Listing NonmetalsNonmetalsin Chemical Formulasin Chemical Formulas

Table 5.1Table 5.1

FFOOClClBrBrIISSHHNNPPCC


Ionic CompoundsIonic Compounds

MetalsMetals + + nonmetalsnonmetals

No individual No individual molecule units, molecule units, instead have a 3-instead have a 3-dimensional array of dimensional array of cationscations and and anionsanions made of made of formula formula unitsunits

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Molecular View of Elements and CompoundsMolecular View of Elements and Compounds


Classify each of the following as either an Classify each of the following as either an atomic element, molecular element, molecular atomic element, molecular element, molecular

compound or ionic compound compound or ionic compound

aluminum, Alaluminum, Al

aluminum chloride, AlClaluminum chloride, AlCl33

chlorine, Clchlorine, Cl22

acetone, Cacetone, C33HH66OO

carbon monoxide, COcarbon monoxide, CO

cobalt, Cocobalt, Co


Classify each of the following as either an Classify each of the following as either an atomic element, molecular element, molecular atomic element, molecular element, molecular

compound or ionic compound compound or ionic compound

aluminum, Al aluminum, Al = atomic element= atomic element

aluminum chloride, AlClaluminum chloride, AlCl33 = ionic = ionic

compoundcompound

chlorine, Clchlorine, Cl22 = molecular element= molecular element

acetone, Cacetone, C33HH66O O = molecular compound= molecular compound

carbon monoxide, CO carbon monoxide, CO = molecular = molecular compoundcompound

cobalt, Co cobalt, Co = atomic element= atomic element


Major Classes of CompoundsMajor Classes of Compounds

IonicIonic– metal + nonmetalmetal + nonmetal

metal first in formulametal first in formula

Binary IonicBinary Ionic

– compounds with polyatomic ionscompounds with polyatomic ions

MolecularMolecular– 2 nonmetals2 nonmetals

Binary Molecular (or Binary Covalent)Binary Molecular (or Binary Covalent)

– AcidsAcids – formula starts with H – formula starts with Hthough acids are molecular, they behave as ionic though acids are molecular, they behave as ionic when dissolved in waterwhen dissolved in water

may be binary or oxyacidmay be binary or oxyacid

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Binary Ionic Compounds:Binary Ionic Compounds:Writing a correct formulaWriting a correct formula

1. Write down the charges of the 1. Write down the charges of the stable ions with the stable ions with the positive ion positive ion first.first.

Ex: for Chlorine and magnesium

Mg Cl 1-2+

1818

2. Cross-over charges to get subscripts. 2. Cross-over charges to get subscripts. Drop all +/- signs.Drop all +/- signs.


Mg Cl1 -2+

1 2

1919

3.3. Reduce/Simplify subscripts to get the Reduce/Simplify subscripts to get the lowest whole number ratio. The subscript lowest whole number ratio. The subscript “1” does not have to be shown.“1” does not have to be shown.


MgCl2

Ex: calcium and sulfur

Ca+2S-2 Ca2S2cross-over CaSsimplify

2020

How many electrons will an atom lose or gain in an ionic compound?

lose

1 e

-

lose

2 e

-

lose

3 e

-

gain

3 e

-

gain

2 e

-

gain

1 e

-

2121

What will be the charge on the What will be the charge on the “stable ion” formed?“stable ion” formed?

+1+2 +3 -3 -2 -1


Rules for Naming Rules for Naming Ionic Ionic CompoundsCompounds from Formula from Formula

Made of Made of cationcation and and anionanionName by simply naming the ionsName by simply naming the ions– If cation is:If cation is:

Type I metal (main group) = metal nameType I metal (main group) = metal nameType II metal (transition element) = metal Type II metal (transition element) = metal name(charge)name(charge)Polyatomic ion = name of polyatomic ionPolyatomic ion = name of polyatomic ion

– If anion is:If anion is:Nonmetal = root of nonmetal name + Nonmetal = root of nonmetal name + ideidePolyatomic ion = name of polyatomic ionPolyatomic ion = name of polyatomic ion


Metal CationsMetal Cations

Type IType I – metals whose ions can only metals whose ions can only

have one possible chargehave one possible charge

IA, IIA, (Al, Ga, In)IA, IIA, (Al, Ga, In)– determine charge by position determine charge by position

on the Periodic Tableon the Periodic Table

IA = +1, IIA = +2, (Al, Ga, In IA = +1, IIA = +2, (Al, Ga, In = +3)= +3)

Type IIType II– metals whose ions can have metals whose ions can have

more than one possible more than one possible charge (transition elements)charge (transition elements)

– determine charge by charge determine charge by charge on anionon anion

How do you know a How do you know a metal cation is Type II?metal cation is Type II?

its not Type I !!!its not Type I !!!


Determine if the following metals are Type I or Determine if the following metals are Type I or Type II. If Type I, determine the charge on the Type II. If Type I, determine the charge on the

cation it forms.cation it forms.

lithium, Lilithium, Li

copper, Cucopper, Cu

gallium, Gagallium, Ga

tin, Sntin, Sn

strontium, Srstrontium, Sr


Determine if the following metals are Type I or Determine if the following metals are Type I or Type II. If Type I, determine the charge on the Type II. If Type I, determine the charge on the

cation it forms.cation it forms.

lithium, Lilithium, Li Type IType I +1+1

copper, Cucopper, Cu Type IIType II

gallium, Gagallium, Ga Type IType I +3+3

tin, Sntin, Sn Type IIType II

strontium, Srstrontium, Sr Type IType I +2+2


Determining Charge and Naming Determining Charge and Naming Monatomic Nonmetal AnionsMonatomic Nonmetal Anions

Determine the charge from position on Determine the charge from position on the Periodic Tablethe Periodic Table

To name anion, change ending on the To name anion, change ending on the element name to element name to ––ideide

4A = -44A = -4 5A = -35A = -3 6A = -26A = -2 7A = -17A = -1

C = C = carbidecarbide

N = nitrideN = nitride O = oxideO = oxide F = fluorideF = fluoride

Si = Si = silicidesilicide

P = P = phosphidephosphide

S = sulfideS = sulfide Cl = Cl = chloridechloride

2727

Naming Type I Binary Ionic CompoundsNaming Type I Binary Ionic Compounds

Contain Contain Metal CationMetal Cation + + Nonmetal AnionNonmetal Anion

Metal listed first in formula & nameMetal listed first in formula & name

1.1. name metal cation first, name nonmetal name metal cation first, name nonmetal anion secondanion second

2.2. cation name is the metal namecation name is the metal name

3.3. nonmetal anion named by changing the nonmetal anion named by changing the ending on the nonmetal name to ending on the nonmetal name to -ide-ide

2828

What is the correct formula and name for What is the correct formula and name for a compound made from:a compound made from:

1. nitrogen and potassium1. nitrogen and potassium

2. magnesium and oxygen2. magnesium and oxygen

3. chlorine and calcium3. chlorine and calcium

4. oxygen and aluminum4. oxygen and aluminum

2929

1. nitrogen and potassiumK3N potassium nitride

2. magnesium and oxygenMgO magnesium oxide

3. chlorine and calciumCaCl2 calcium chloride

4. oxygen and aluminumAl2O3 aluminum oxide


Naming Type II Binary Ionic CompoundsNaming Type II Binary Ionic Compounds

Name metal cation first, name nonmetal Name metal cation first, name nonmetal anion secondanion second

Metal cation nameMetal cation name is the metal name is the metal name followed by a followed by a Roman Numeral in Roman Numeral in parentheses to indicate its chargeparentheses to indicate its charge

– determine charge from anion chargedetermine charge from anion charge– Common Type II cations in Table 5.5Common Type II cations in Table 5.5

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


Example – Naming Binary Ionic, Type II MetalExample – Naming Binary Ionic, Type II Metal

CuClCuCl

1.1. Identify Major ClassIdentify Major ClassCu = metal, on left side of Periodic TableCu = metal, on left side of Periodic Table

Cl = nonmetal, on right side of Periodic TableCl = nonmetal, on right side of Periodic Table

IonicIonic

2.2. Identify the Subclass Identify the Subclass 2 elements, 2 elements,

Binary IonicBinary Ionic

3.3. Is the metal Type I or Type IIIs the metal Type I or Type IICu not in Group IA, IIA, or (Al, Ga, In) Cu not in Group IA, IIA, or (Al, Ga, In) Type II Type II


Example – Naming Binary Ionic, Type II MetalExample – Naming Binary Ionic, Type II Metal CuClCuCl

4.4. Identify Identify cationcation and and anionanionClCl = = ClCl-- because it is Group 7 because it is Group 7CuCu = = CuCu++ to balance the charge to balance the charge

5.5. Name the cationName the cationCuCu++ = copper( = copper(II))

6.6. Name the anionName the anionClCl-- = chloride = chloride

7.7. Write the cation name first, then the Write the cation name first, then the anion nameanion name

copper(copper(II) chloride) chloride

3333

Give the formula and name for a Give the formula and name for a compound from Cucompound from Cu+1+1 and sulfur and sulfur

Cu+1 S-2

formula = Cu2S

name = copper(I) sulfide

3434

Give the formula and name for a Give the formula and name for a compound from compound from FeFe+2+2 and and chlorinechlorine

Fe+2 Cl-1 formulaformula = FeClFeCl22

namename = = iron(iron(IIII) chloride) chloride

Give the formula and name for a Give the formula and name for a compound from compound from CuCu+2+2 and and sulfursulfur

Cu+2 S-2 formula = formula = CuSCuS

name = name = copper(copper(IIII) sulfide) sulfide

3535

What is the formula for copper(What is the formula for copper(IIII) ) oxide?oxide?

Cu+2 O-2

formula = CuO


Compounds with Compounds with Polyatomic IonsPolyatomic Ions

Polyatomic ionsPolyatomic ions are single ions that are single ions that contain more than one atomcontain more than one atom

Formula: cation first, polyatomic anion or Formula: cation first, polyatomic anion or polyatomic cation, monatomic anionpolyatomic cation, monatomic anion

Name cation first and then anionName cation first and then anion– Non-polyatomic cations named like Type I and Non-polyatomic cations named like Type I and

IIII– Non-polyatomic anions named with Non-polyatomic anions named with ––ideide– Polyatomic ionsPolyatomic ions = use name of polyatomic ion = use name of polyatomic ion


Some Common Polyatomic IonsSome Common Polyatomic Ions(be able to recognize these)(be able to recognize these)NameName Formula and ChargeFormula and Chargeacetateacetate CC22HH33OO22

––

carbonatecarbonate COCO3322––

hydrogen carbonatehydrogen carbonate(aka bicarbonate)(aka bicarbonate)

HCOHCO33––

hydroxidehydroxide OHOH––

nitratenitrate NONO33––

nitritenitrite NONO22––

sulfatesulfate SOSO4422––

chloratechlorate ClOClO33––

ammoniumammonium NHNH44++


Naming Ionic Compounds with Polyatomic IonNaming Ionic Compounds with Polyatomic Ion NaNa22SOSO44

1.1. Identify Major ClassIdentify Major ClassNa = metal, on the left side of Periodic TableNa = metal, on the left side of Periodic Table

SOSO44 = is a polyatomic ion, = is a polyatomic ion, Ionic Ionic

2.2. Identify the SubclassIdentify the Subclasscompound has 3 elements compound has 3 elements Ionic with Ionic with

Polyatomic IonPolyatomic Ion

3.3. Is the metal Type I or Type IIIs the metal Type I or Type IINa is in Group IA, Na is in Group IA, Type I Type I


4.4. Identify the ionsIdentify the ionsNa = NaNa = Na+ + because in Group 1because in Group 1

SOSO44 = SO = SO442-2- a polyatomic ion a polyatomic ion

5.5. Name the cationName the cationNaNa++ = sodium (Type I) = sodium (Type I)

6.6. Name the anionName the anion

SOSO442-2- = sulfate = sulfate

7.7. Write the name of the cation followed by Write the name of the cation followed by the name of the anionthe name of the anion

sodium sulfatesodium sulfate

Naming Ionic Compounds with Polyatomic IonNaming Ionic Compounds with Polyatomic Ion NaNa22SOSO44


Naming Ionic Compounds with Polyatomic IonNaming Ionic Compounds with Polyatomic Ion Fe(NOFe(NO33))33

1.1. Identify Major ClassIdentify Major ClassFe = metal, on left side of Periodic TableFe = metal, on left side of Periodic Table

NONO33 = is a polyatomic ion because it is in ( ) = is a polyatomic ion because it is in ( )

IonicIonic

2.2. Identify the SubclassIdentify the SubclassHave 3 elements Have 3 elements Ionic with Polyatomic Ion Ionic with Polyatomic Ion

3.3. Is the metal Type I or Type IIIs the metal Type I or Type IIFe not in Group IA, IIA, or (Al, Ga, In) Fe not in Group IA, IIA, or (Al, Ga, In) Type II Type II


Naming Ionic compounds with Polyatomic IonNaming Ionic compounds with Polyatomic Ion

Fe(NOFe(NO33))335.5. Identify the ionsIdentify the ions

NONO33 = NO = NO33-- a polyatomic ion a polyatomic ion

Fe = FeFe = Fe+3+3 to balance the charge of the 3 NO to balance the charge of the 3 NO33-1-1

6.6. Name the cationName the cationFeFe+3+3 = iron( = iron(IIIIII) (Type ) (Type IIII))

7.7. Name the anionName the anion

NONO33-- = nitrate = nitrate

8.8. Write the name of the cation followed by Write the name of the cation followed by the name of the anionthe name of the anion

iron(iron(IIIIII) nitrate) nitrate


Rules for Naming Binary Rules for Naming Binary Molecular Compounds Molecular Compounds

Binary molecularBinary molecular compounds = compounds = composed of composed of 2 nonmetal elements2 nonmetal elementsfor binary molecular compound:for binary molecular compound:– name first nonmetalname first nonmetal– then name second nonmetal with then name second nonmetal with ideide

endingending– then give each name a then give each name a prefixprefix to indicate to indicate

number of atoms number of atoms (subscript)(subscript) of each of each element in formulaelement in formula

4343

Naming Binary Molecular Compounds Naming Binary Molecular Compounds

1.1. Name first element in formula first Name first element in formula first – use the full name of the elementuse the full name of the element

2.2. Name the second element in the formula with Name the second element in the formula with an an -ide-ide

– as if it were an anion, as if it were an anion, however, remember these however, remember these compounds do not contain ionscompounds do not contain ions!!

3.3. Use a prefix in front of each name to indicate Use a prefix in front of each name to indicate the number of atomsthe number of atoms

a)a) Never use the prefix Never use the prefix mono-mono- on the first element on the first element


Subscript - PrefixesSubscript - Prefixes1 = mono-; 1 = mono-; – not used on first nonmetalnot used on first nonmetal

2 = di-2 = di-3 = tri-3 = tri-4 = tetra-4 = tetra-5 = penta-5 = penta-6 = hexa-6 = hexa-7 = hepta-7 = hepta-8 = octa-8 = octa-drop last “a” if name begins with voweldrop last “a” if name begins with vowel


Naming Binary Molecular CompoundsNaming Binary Molecular Compounds BFBF33

1.1. Identify Major ClassIdentify Major ClassB = nonmetal, on right side of Periodic B = nonmetal, on right side of Periodic

TableTable

F = nonmetal, on right side of Periodic F = nonmetal, on right side of Periodic TableTable

MolecularMolecular

2.2. Identify the SubclassIdentify the Subclass2 elements 2 elements Binary Molecular Binary Molecular


Naming Binary Molecular CompoundsNaming Binary Molecular Compounds BFBF33

4.4. Name the first element: Name the first element: boronboron5.5. Name the second element with an Name the second element with an –ide–ide

fluorine fluorine fluor fluorideide6.6. Add a prefix to each name to indicate the Add a prefix to each name to indicate the

subscriptsubscriptmonoboron, trifluoridemonoboron, trifluoride

7.7. Write the first element with prefix, then the Write the first element with prefix, then the second element with prefixsecond element with prefix

– Drop prefix Drop prefix monomono from first element from first element

boron trifluorideboron trifluoride


Formula MassFormula Mass

Formula massFormula mass = mass of an individual = mass of an individual molecule or formula unitmolecule or formula unit

also known as also known as molecular mass or molecular molecular mass or molecular weightweight

SumSum of the masses of the atoms in a single of the masses of the atoms in a single molecule or formula unitmolecule or formula unit– whole = sum of the parts!whole = sum of the parts!

mass of 1 molecule of Hmass of 1 molecule of H22O O

= 2(1.01 amu H) + 16.00 amu O = 18.02 amu= 2(1.01 amu H) + 16.00 amu O = 18.02 amu

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Introductory Chemistry, 2 nd Edition Nivaldo Tro Chapter 5 Molecules and Compounds.

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