5.2 Molecular Substances5.2 Molecular Substances

ObjectivesObjectives

Compare the properties of molecular Compare the properties of molecular and ionic substances.and ionic substances.

Distinguish among allotropes of an Distinguish among allotropes of an element.element.

Apply formulas to name molecular Apply formulas to name molecular compounds.compounds.

Properties of Molecular Properties of Molecular SubstanceSubstance

Molecular substanceMolecular substance- a substance - a substance that has atoms held together by that has atoms held together by covalent bondscovalent bonds

Properties are more variableProperties are more variable Polyethylene plastic = softPolyethylene plastic = soft Quartz = hardQuartz = hard

PropertiesProperties

Low melting and boiling pointsLow melting and boiling points Less soluble in waterLess soluble in water Not electrolytesNot electrolytes Interparticles forces between Interparticles forces between

molecules are weak and easily molecules are weak and easily broken.broken. Explains the softness and low melting Explains the softness and low melting

points of most molecular substancespoints of most molecular substances

Properties Properties

Different enough that the differences Different enough that the differences can be used to classify and can be used to classify and separated them from one another.separated them from one another. Distillation- method of separating Distillation- method of separating

substances in a mixture by evaporation substances in a mixture by evaporation of liquid and subsequence condensation of liquid and subsequence condensation of its vapor.of its vapor.

Molecular ElementsMolecular Elements

Molecules vary greatly in sizeMolecules vary greatly in size Most elements occur in nature Most elements occur in nature

bonded to another element, but bonded to another element, but some occurs as atoms of the same some occurs as atoms of the same element bonded together.element bonded together.

Molecular elements-Molecular elements- atoms of the atoms of the same element bonded together.same element bonded together. Why? For stability.Why? For stability.

Diatomic ElementsDiatomic Elements Seven nonmetal elements are found Seven nonmetal elements are found

naturally as molecular elements of naturally as molecular elements of two identical atoms.two identical atoms. DiatomicDiatomic

Hydrogen – HHydrogen – H2 2 - Gas- Gas Nitrogen – NNitrogen – N2 2 - Gas- Gas Oxygen – OOxygen – O2 2 - Gas- Gas Fluorine – FFluorine – F2 2 - Gas- Gas Chlorine – ClChlorine – Cl2 2 - Gas- Gas Bromine – BrBromine – Br22 - Liquid - Liquid Iodine – IIodine – I2 2 - Solid- Solid

Electron Configuration of Electron Configuration of Diatomic ElementsDiatomic Elements

OxygenOxygen

ChlorineChlorine

NitrogenNitrogen

AllotropesAllotropes

AllotropesAllotropes-molecules of a single -molecules of a single element that differ in crystalline or element that differ in crystalline or molecular structure.molecular structure. Oxygen and OzoneOxygen and Ozone Ozone is the most common form in Ozone is the most common form in

atomsphereatomsphere Structural differencesStructural differences

OzoneOzone

Occurs naturally and is formed from diatomic Occurs naturally and is formed from diatomic oxygen by lightning or ultraviolet light.oxygen by lightning or ultraviolet light.

Sharp odorSharp odor Also formed from TV sets or computer monitorsAlso formed from TV sets or computer monitors Ozone is harmful to living thingsOzone is harmful to living things UsesUses

Small amounts of ozone is used to purify waterSmall amounts of ozone is used to purify water Treat clothing, carpeting and other material damaged by Treat clothing, carpeting and other material damaged by

smokesmoke Used to remove cigarette smellUsed to remove cigarette smell Layer high in our atmosphere helps to shield organisms Layer high in our atmosphere helps to shield organisms

from harmful UV radiationfrom harmful UV radiation

Phosphorus AllotropesPhosphorus Allotropes

Three allotropesThree allotropes WhiteWhite-will ignite spontaneously in air -will ignite spontaneously in air

and must be stored under waterand must be stored under water RedRed-used in the strike pad of safety -used in the strike pad of safety

matchesmatches BlackBlack- is a semiconductor- is a semiconductor Each has unique structure and Each has unique structure and

propertiesproperties Figure 5.15 p. 179Figure 5.15 p. 179

Carbon AllotropesCarbon Allotropes

Several important onesSeveral important ones GraphiteGraphite Carbon BlacksCarbon Blacks DiamondDiamond CharcoalsCharcoals FullerenesFullerenes Linear Acetylenic CarbonLinear Acetylenic Carbon

GraphiteGraphite

Most common form of carbonMost common form of carbon Atoms are linked to each other in a Atoms are linked to each other in a

continuous sheet of hexagonscontinuous sheet of hexagons Well organized structureWell organized structure The looseness between layers is why The looseness between layers is why

graphite is useful to write with.graphite is useful to write with.

Carbon BlacksCarbon Blacks

Make up most of the soot that collects in Make up most of the soot that collects in chimneyschimneys

Formed by the incomplete burning of Formed by the incomplete burning of hydrocarbon compounds.hydrocarbon compounds.

Each microscopic chunk of carbon is make Each microscopic chunk of carbon is make up of millions of jumbled chunks of up of millions of jumbled chunks of layered carbon atoms.layered carbon atoms.

Lack organizationLack organization Used in the production of printing inks and Used in the production of printing inks and

rubber products.rubber products.

DiamondDiamond

Hardest natural substanceHardest natural substance Often used on the tips of cutting tools and Often used on the tips of cutting tools and

drills.drills. Structure: every carbon atom is attached to Structure: every carbon atom is attached to

four other carbon atomsfour other carbon atoms One of the most organized of all substancesOne of the most organized of all substances

This organization of covalent bonds accounts for This organization of covalent bonds accounts for the hardness of diamonds.the hardness of diamonds.

Formed under extreme pressure and Formed under extreme pressure and temperature.temperature. Diamonds range in age from 600 million to 3 Diamonds range in age from 600 million to 3

billion years oldbillion years old

CharcoalsCharcoals

Poorly organized carbon molecules.Poorly organized carbon molecules. Produced from the burning of organic Produced from the burning of organic

mattermatter Charcoal is extremely porous Charcoal is extremely porous

great surface areagreat surface area Useful for removing odors and Useful for removing odors and

tastes(activated charcoal)tastes(activated charcoal)

FullerenesFullerenes

Unusually stableUnusually stable Group of highly organized allotropes with Group of highly organized allotropes with

even-numbered molecular formulaseven-numbered molecular formulas The buckminsterfullerene, CThe buckminsterfullerene, C6060 discovered in discovered in

1985 in soot and the shape confirmed in 1985 in soot and the shape confirmed in 1991 (p. 178)1991 (p. 178)

Some molecules are hollow spheres other Some molecules are hollow spheres other are hollow tubes with great flexibility.are hollow tubes with great flexibility. After crashing into steel plates at a speed of After crashing into steel plates at a speed of

7000 m/s the rebound with their original shape 7000 m/s the rebound with their original shape intact.intact.

Potential use as superconductorsPotential use as superconductors

Linear Acetylenic CarbonLinear Acetylenic Carbon Threadlike allotrope organized into long Threadlike allotrope organized into long

spirals of bonded carbonsspirals of bonded carbons Each spiral contains 300-500 carbon atoms.Each spiral contains 300-500 carbon atoms. Produced by using a laser to zap a graphite Produced by using a laser to zap a graphite

rod into a glass container filled with argon rod into a glass container filled with argon gas. The allotrope splatters on the glass and gas. The allotrope splatters on the glass and is then removed.is then removed.

Used in microelectronicsUsed in microelectronics Some linear acetylenic carbons may Some linear acetylenic carbons may

eventually form fullerenes, whereas other eventually form fullerenes, whereas other form soot.form soot.

Naming Binary Inorganic Naming Binary Inorganic CompoundsCompounds

Organic compoundsOrganic compounds- compounds that - compounds that contain carboncontain carbon

Inorganic compoundsInorganic compounds- compounds - compounds that do not contain carbonthat do not contain carbon

Molecular Binary CompoundsMolecular Binary Compounds Contain only two nonmetal elementsContain only two nonmetal elements bonded covalentlybonded covalently

NamingNaming

Write out the name of the first nonmetalWrite out the name of the first nonmetal Follow it by naming the second nonmetal Follow it by naming the second nonmetal

with its ending changed to with its ending changed to –ide–ide You write the first the element that is farther to You write the first the element that is farther to

the left on the periodic table, with the the left on the periodic table, with the exceptions of a few compounds that contain exceptions of a few compounds that contain hydrogen.hydrogen.

If the elements are in the same group, name If the elements are in the same group, name first the element that is closer to the bottom of first the element that is closer to the bottom of the periodic tablethe periodic table

A prefix is need when more than one atom A prefix is need when more than one atom is present for the first of the two and always is present for the first of the two and always used for the second atom of a moleculeused for the second atom of a molecule

Prefixes Prefixes

When a vowel combination (o-o or a-o) appears When a vowel combination (o-o or a-o) appears next to each other the first of the pair is usually next to each other the first of the pair is usually omitted.omitted. Mono- = 1Mono- = 1 Di- = 2Di- = 2 Tri- = 3Tri- = 3 Tetra- = 4Tetra- = 4 Penta- = 5 Penta- = 5 Hexa- = 6Hexa- = 6 Hepta- = 7Hepta- = 7 Octa- = 8Octa- = 8 Nona- = 9Nona- = 9 Deca- = 10Deca- = 10

Let’s Try It!Let’s Try It!

Name the following molecular compoundsName the following molecular compounds NONO

NONO22

NN22OO

NN22OO55

Let’s Try It!Let’s Try It!

Write the formula for the following Write the formula for the following molecular compounds.molecular compounds. Carbon disulfideCarbon disulfide

Carbon monoxideCarbon monoxide

Sulfur hexafluorideSulfur hexafluoride

Dinitrogen trioxideDinitrogen trioxide

Common NamesCommon Names

A few inorganic compounds have A few inorganic compounds have common names that all scientists common names that all scientists use in place of formal names.use in place of formal names.

Examples:Examples: WaterWater Ammonia Ammonia Also acids and basesAlso acids and bases

Table 5. 7 Names of Common Table 5. 7 Names of Common Acids and BasesAcids and Bases

FormulaFormula NameNameAcidsAcids

HClHCl

HH22SOSO44

HH33POPO44

HNOHNO33

HCHC22HH33OO22

BasesBases

NaOHNaOH

KOHKOH

NHNH33

Hydrochloric acidHydrochloric acid

Sulfuric acidSulfuric acid

Phosphoric acidPhosphoric acid

Nitric acidNitric acidAcetic acid Acetic acid (organic (organic compound)compound)

Sodium hydroxideSodium hydroxide

Potassium hydroxidePotassium hydroxide

ammoniaammonia

Naming Organic CompoundsNaming Organic Compounds

The name of even the most complex organic The name of even the most complex organic compound is based on the name of a compound is based on the name of a hydrocarbon.hydrocarbon.

HydrocarbonHydrocarbon- a organic compound that - a organic compound that contains only the elements hydrogen and contains only the elements hydrogen and carbon.carbon. Occur naturally in fossil fuelsOccur naturally in fossil fuels Used mainly as fuels and the raw materials for Used mainly as fuels and the raw materials for

making other organic compoundsmaking other organic compounds Carbon can form four covalent bonds.Carbon can form four covalent bonds.

Table 5.8 HydrocarbonsTable 5.8 HydrocarbonsFormulaFormula NameName

CHCH44

CC22HH66

CC33HH88

CC44HH1010

CC55HH1212

CC66HH1414

CC77HH1616

CC88HH1818

CC99HH2020

CC1010HH2222

MethaneMethane

EthaneEthane

PropanePropane

ButaneButane

PentanePentane

HexaneHexane

HeptaneHeptane

OctaneOctane

NonaneNonane

decanedecane

Connecting IdeasConnecting Ideas

Formulas represent the know Formulas represent the know composition of real substancescomposition of real substances

But just because you can write the But just because you can write the formula does not mean it can exist.formula does not mean it can exist.

ReviewReview

Compare ionic and molecular Compare ionic and molecular compounds.compounds.

What are the allotropes of carbon What are the allotropes of carbon and something about each?and something about each?

What are the allotropes of What are the allotropes of phosphorous and something about phosphorous and something about each?each?

HomeworkHomework

Read p. 176-178 and answer questions 1-3Read p. 176-178 and answer questions 1-3 P. 181 #7 & 8P. 181 #7 & 8 P. 183 #1-3P. 183 #1-3