Chapter 4Chapter 4

The Structure of The Structure of MatterMatter

4.14.1Compounds & MoleculesCompounds & Molecules

A compound is different from the A compound is different from the elements it contains.elements it contains.

NaCl, Sodium chloride, is totally NaCl, Sodium chloride, is totally different than the metal, sodium, or different than the metal, sodium, or the gas, chlorine.the gas, chlorine.

Chemical bonds distinguish Chemical bonds distinguish compounds from mixturescompounds from mixtures

The forces that hold compounds together The forces that hold compounds together are called are called chemical bonds.chemical bonds.

During a chemical reaction During a chemical reaction chemical chemical bonds bonds are broken & atoms are are broken & atoms are re-re-arrangedarranged to form a new substance to form a new substance..

A compound has a specific formulaA compound has a specific formula

The formula for water is HThe formula for water is H2OOThe formula for table sugar is The formula for table sugar is CC1212HH2222OO1111. . Compounds are Compounds are alwaysalways made of made of specific elements in specific numbers.specific elements in specific numbers.

A molecule of water is always HA molecule of water is always H22O. O. [[twotwo hydrogen atoms bonded to hydrogen atoms bonded to oneone oxygen atom.]oxygen atom.]

Chemical structureChemical structure illustrates the illustrates the bonding within a compoundbonding within a compound

The way the atoms are arranged in a The way the atoms are arranged in a compound determine many of its properties.compound determine many of its properties.

[water is polar; oil is non-polar][water is polar; oil is non-polar]

Two terms are used to specify the positions Two terms are used to specify the positions of atoms relative to one another. of atoms relative to one another. – 1. 1. Bond lengthBond length: the average distance between : the average distance between

the nuclei of the 2 bonded atomsthe nuclei of the 2 bonded atoms– 2. 2. Bond angleBond angle: the angle formed by two bonds to : the angle formed by two bonds to

the same atomthe same atom

Models of CompoundsModels of Compounds

A model helps you to “visualize” A model helps you to “visualize” something.something.

1. 1. Ball & stickBall & stick model: ball is the atom model: ball is the atom & the stick is the bond.& the stick is the bond.

2. Structural formulas: 2. Structural formulas: use symbols & use symbols & lines to depict the structure.lines to depict the structure.3. 3. Space filling Space filling model: can’t “see” the model: can’t “see” the bonds. [bonds. [Fig. 4.4 P.111]Fig. 4.4 P.111]

StructureStructureDifferent structures give compounds Different structures give compounds different properties.different properties.

Network structureNetwork structure: : SiO2 is an ionic is an ionic

compoundcompound whichwhich has a strong, rigid has a strong, rigid structure. All the angles are the same structure. All the angles are the same (109.5(109.5oo). ).

This is why rocks containing This is why rocks containing SiO2 are hard are hard & inflexible. It takes a lot of energy to & inflexible. It takes a lot of energy to break these bonds. (high melting point)break these bonds. (high melting point)

Some network bonds are ionicSome network bonds are ionic

Some networks are made of bonded Some networks are made of bonded ions (charged particles). NaCl is ions (charged particles). NaCl is made of a network of tightly packed made of a network of tightly packed positive Napositive Na++ and negative Cl and negative Cl-- ions. ions.

The result is strong, rigid bonds that The result is strong, rigid bonds that have high melting & boiling points.have high melting & boiling points.

Ionic bonds occur between a positive Ionic bonds occur between a positive metal ion & a negative nonmetal ion.metal ion & a negative nonmetal ion.

Some compounds are moleculesSome compounds are molecules

Molecules are made when nonmetals Molecules are made when nonmetals combine with nonmetals. combine with nonmetals.

The bonds can be weak or strong.The bonds can be weak or strong.

Molecules of gases have little Molecules of gases have little attraction to each other, so they attraction to each other, so they spread out & fill any size container.spread out & fill any size container.

Strength of attraction between Strength of attraction between moleculesmolecules

Attraction forces are greatest in solids.Attraction forces are greatest in solids.

Attraction forces are less in liquids, and even Attraction forces are less in liquids, and even less in gasses. less in gasses. (see data table 4.2 on p. 113)(see data table 4.2 on p. 113)

The higher melting & boiling points of water are The higher melting & boiling points of water are due to the strong bonds within the water due to the strong bonds within the water molecule. molecule.

Each water molecule is attracted to the Each water molecule is attracted to the molecule next to it, due to the polar nature of molecule next to it, due to the polar nature of the molecule.the molecule.

Teacher demo p.113Teacher demo p.113

4.24.2Ionic & Covalent BondingIonic & Covalent Bonding

Atoms bond when their valence Atoms bond when their valence electrons interact. electrons interact.

When atoms gain or lose electrons When atoms gain or lose electrons they form they form ionic compoundsionic compounds..

When atoms share electrons they When atoms share electrons they form form moleculesmolecules..

4.24.2Ionic & Covalent BondingIonic & Covalent Bonding

Bonds between atoms act like Bonds between atoms act like flexible springsflexible springs, because they can , because they can bend & stretch without breakingbend & stretch without breaking

Ionic BondsIonic BondsIonic bonds occur between ions of Ionic bonds occur between ions of opposite charge.opposite charge.

MetalsMetals lose electrons to become lose electrons to become positive ions, called cations.positive ions, called cations.

NonmetalsNonmetals gain electrons to become gain electrons to become negative ions, called anions.negative ions, called anions.

Ratio’sRatio’sNaCl means 1 atom of Na is bonded NaCl means 1 atom of Na is bonded to 1 atom of Cl.to 1 atom of Cl.The NaThe Na++ is attracted to the Cl is attracted to the Cl-- (opposites (opposites attract).attract).

Within a network there are millions of Within a network there are millions of positive ions being attracted to the positive ions being attracted to the millions of negative ions. NaCl is the millions of negative ions. NaCl is the formula unitformula unit..The formula unit varies according to The formula unit varies according to the compound. Ex.: CaFthe compound. Ex.: CaF22

Ionic compounds conduct electricity Ionic compounds conduct electricity when meltedwhen melted

Electric current is the result of Electric current is the result of moving charges.moving charges.

When in solid form, ionic compounds When in solid form, ionic compounds do notdo not conduct electricity because conduct electricity because the ions are locked in position the ions are locked in position (crystal).(crystal).

However, in liquid form, the ions are However, in liquid form, the ions are free to move about and they free to move about and they dodo conduct electricity conduct electricity

Metallic BondsMetallic BondsMetals conduct electricity, are Metals conduct electricity, are malleable & ductile.malleable & ductile.Electrons move freely between metal Electrons move freely between metal atoms. “sea of electrons”atoms. “sea of electrons”The atoms are packed so closely that The atoms are packed so closely that the valence electrons overlap each the valence electrons overlap each other other (sea of electrons).(sea of electrons). This frees up the This frees up the electrons to move from atom to atom.electrons to move from atom to atom.Remember, electricity is the result of Remember, electricity is the result of moving charges.moving charges.

Covalent BondsCovalent Bonds

Covalent bonds form molecules Covalent bonds form molecules (nonmetals bonding to nonmetals)(nonmetals bonding to nonmetals)

Covalent compounds can be solid, Covalent compounds can be solid, liquid or gas.liquid or gas.

Most covalent substances have low Most covalent substances have low melting points.melting points.

Covalent bonds do not conduct Covalent bonds do not conduct electricity.electricity.

Covalent bonds share electronsCovalent bonds share electrons

Electrons are shared so that both Electrons are shared so that both atoms achieve the “magic number” atoms achieve the “magic number” of chemistry – 8, valence electrons.of chemistry – 8, valence electrons.

If the shared electrons are equally If the shared electrons are equally attracted to each nucleus, they attracted to each nucleus, they produce a nonpolar covalent bond.produce a nonpolar covalent bond.The sharing is represented by a The sharing is represented by a single line between the atoms. single line between the atoms. See p.119See p.119

Atoms may share more than 1 pair Atoms may share more than 1 pair of electronsof electrons

In a In a doubledouble covalent bond, 2 pairs of covalent bond, 2 pairs of electrons are shared. electrons are shared.

In a In a tripletriple covalent bond, 3 pairs covalent bond, 3 pairs electrons are shared.electrons are shared.

Triple bonds are stronger than Triple bonds are stronger than double bonds.double bonds.

Triple & double bonds are shorter Triple & double bonds are shorter than single bonds.than single bonds.

Electrons are not always equally Electrons are not always equally sharedshared

In some instances electrons are In some instances electrons are attracted more to one nucleus than attracted more to one nucleus than another.another.This results in a This results in a polarpolar molecule.molecule.Usually electrons are more attracted Usually electrons are more attracted to elements on the upper right side to elements on the upper right side of the Periodic Table.of the Periodic Table.Water is a good example of a polar Water is a good example of a polar molecule.molecule.

Polyatomic ionsPolyatomic ionsSome compounds have both ionic and Some compounds have both ionic and covalent bonds; such compounds contain covalent bonds; such compounds contain polyatomic ions.polyatomic ions.Polyatomic ions are groups of covalently Polyatomic ions are groups of covalently bonded atoms that have either lost or gained bonded atoms that have either lost or gained electrons.electrons.Polyatomic ions act just like normal ions.Polyatomic ions act just like normal ions.Parentheses are used to denote when more Parentheses are used to denote when more than one ion is bonded to another.than one ion is bonded to another.The corresponding subscript indicates that The corresponding subscript indicates that everything inside the parentheses is effected everything inside the parentheses is effected by that subscript. by that subscript.

Naming the polyatomic ionsNaming the polyatomic ions-ite & -ate are suffixes that indicate the -ite & -ate are suffixes that indicate the presence of oxygen.presence of oxygen.These endings do NOT tell you how many These endings do NOT tell you how many oxygen atoms are present.oxygen atoms are present.If there is –ate at the end of the name, If there is –ate at the end of the name, there is 1there is 1 more more oxygen atom than if there oxygen atom than if there is an –ite at the end.is an –ite at the end.The charge is the same for each ion The charge is the same for each ion Some have neither –ite or –ate, these Some have neither –ite or –ate, these don’t follow the rules.don’t follow the rules.

4.34.3Compound Names & FormulasCompound Names & Formulas

Naming ionic compounds – cations & Naming ionic compounds – cations & anions form compounds with strong bonds.anions form compounds with strong bonds.

Both elements’ names are represented in Both elements’ names are represented in the name. Ex.: BaFthe name. Ex.: BaF22 is Barium Fluoride. is Barium Fluoride.

In many cases, the name of the cation is In many cases, the name of the cation is simply the name of the element.simply the name of the element.When the anion is made of 1 element, the When the anion is made of 1 element, the anion has a name similar to the name of anion has a name similar to the name of the element but the ending is different. the element but the ending is different. See See fig. 4.5 on p. 124fig. 4.5 on p. 124

Some cation names reflect the Some cation names reflect the chargecharge

According to what we have learned, FeO According to what we have learned, FeO and Feand Fe22OO33 should both be called iron oxide. should both be called iron oxide.

Iron (Fe) is a transition metal.Iron (Fe) is a transition metal.

Transition metals can lose 1 or 2 or 3 Transition metals can lose 1 or 2 or 3 valence electrons. To distinguish between valence electrons. To distinguish between the two a Roman numeral is added in the two a Roman numeral is added in parentheses. parentheses.

The Roman numeral tells the chargeThe Roman numeral tells the charge

Iron (III) oxide tells us iron is FeIron (III) oxide tells us iron is Fe3+3+

(a cation (a cation that lost 3 electrons).that lost 3 electrons).

Determining the charge of transition Determining the charge of transition metalsmetals

Total charge of every compound must be Total charge of every compound must be zero.zero.

In FeIn Fe22OO33 there are 3 oxygen atoms. there are 3 oxygen atoms.Oxygen & all elements in column 6 have Oxygen & all elements in column 6 have oxidation #’s of 2-oxidation #’s of 2-3 oxygen atoms times – 2 charge = -63 oxygen atoms times – 2 charge = -6To total zero for the whole compound, iron To total zero for the whole compound, iron must have a charge of +6.must have a charge of +6.There are 2 iron atoms, so each must have a There are 2 iron atoms, so each must have a +3 charge+3 chargeTherefore we are working with iron (III)Therefore we are working with iron (III)

Naming Covalent BondsNaming Covalent BondsWith two element covalent bonds, With two element covalent bonds, numerical prefixes tell us the number numerical prefixes tell us the number of atoms present in the compound.of atoms present in the compound.

If there is only 1 atom of the 1If there is only 1 atom of the 1stst element listed, there is no prefix. For element listed, there is no prefix. For 2 atoms use the prefix 2 atoms use the prefix di-di-, for 3 , for 3 atoms atoms tri-tri- etc. etc.

The element furthest to the right on The element furthest to the right on the Periodic Table is named 2the Periodic Table is named 2ndnd & & ends in ends in -ide-ide

Naming Covalent CompoundsNaming Covalent CompoundsMono-Mono- OneOne

Di-Di- TwoTwo

Tri-Tri- ThreeThree

Tetra-Tetra- FourFour

Penta-Penta- FiveFive

Hexa-Hexa- SixSix

Hepta-Hepta- SevenSeven

Octa-Octa- EightEight

Nona-Nona- NineNine

Deca-Deca- TenTen

Naming Covalent CompoundsNaming Covalent Compounds

BFBF33 Boron trifluorideBoron trifluoride

NN22OO44 Dinitrogen tetroxideDinitrogen tetroxide

A compound’s simplest formula is A compound’s simplest formula is its empirical formulaits empirical formula

Empirical formula: the smallest whole Empirical formula: the smallest whole number ratio of the atoms in a compound.number ratio of the atoms in a compound.We use the molecular formula to denote We use the molecular formula to denote exactly how many atoms are in one exactly how many atoms are in one molecule of a compound.molecule of a compound.Some compounds have the same empirical Some compounds have the same empirical formula, but different molecular formulas. formula, but different molecular formulas. For example, formaldehyde, CHFor example, formaldehyde, CH22O; acetic O; acetic acid, Cacid, C22HH44OO22; ; & glucose, C& glucose, C66HH1212OO66 – – all have all have the empirical formula of CHthe empirical formula of CH22OO

4.44.4Organic & Biochemical CompoundsOrganic & Biochemical Compounds

An organic compound is a covalently An organic compound is a covalently bonded compound made of molecules.bonded compound made of molecules.Organic compounds contain carbon & Organic compounds contain carbon & usually hydrogen.usually hydrogen.When a compound has only carbon & When a compound has only carbon & hydrogen it is called a hydrogen it is called a hydrocarbon.hydrocarbon.Methane, CHMethane, CH44, has 4 single bonds. , has 4 single bonds. Methane is formed when living matter Methane is formed when living matter decays.decays.Carbon can also form double bonds when Carbon can also form double bonds when it shares 2 of its electrons. Triple bonds it shares 2 of its electrons. Triple bonds are also possible but carbon can never are also possible but carbon can never forms more than 4 bonds.forms more than 4 bonds.

AlkanesAlkanes

An alkane is a hydrocarbon that has An alkane is a hydrocarbon that has only single bonds – like we only single bonds – like we mentioned for CHmentioned for CH44..

Alkanes can have C-H bonds or C-C Alkanes can have C-H bonds or C-C bonds.bonds.

Alkanes names end in –ane.Alkanes names end in –ane.

AlkenesAlkenes

Hydrocarbons that have at least 1 Hydrocarbons that have at least 1 double bond, C=Cdouble bond, C=C

Alkenes names end in –ene.Alkenes names end in –ene.

AlcoholsAlcoholsAlcohols are organic compounds that Alcohols are organic compounds that contain hydrogen, carbon & oxygen.contain hydrogen, carbon & oxygen.

Alcohols have hydroxyl or –OH Alcohols have hydroxyl or –OH groupsgroups

PolymersPolymersA polymer is a large organic molecule made of A polymer is a large organic molecule made of many smaller bonds.many smaller bonds.Small organic molecules bond to form long Small organic molecules bond to form long chains called polymers.chains called polymers.Polymers are found in your body, wood, rubber Polymers are found in your body, wood, rubber & plastic.& plastic.Rubber, wood, cotton are examples of natural Rubber, wood, cotton are examples of natural polymers.polymers.Man-made polymers are usually either plastic Man-made polymers are usually either plastic or fibers.or fibers.The structure determines its properties, just as The structure determines its properties, just as for other compounds.for other compounds.Polymers are likened to a bowl of spaghetti, Polymers are likened to a bowl of spaghetti, tangled but can slide over one another. tangled but can slide over one another.

Biochemical CompoundsBiochemical CompoundsA biochemical compound is any organic A biochemical compound is any organic compound that is important to living compound that is important to living things.things.Some examples include carbohydrates for Some examples include carbohydrates for energy & proteins that form all the organs energy & proteins that form all the organs in our body.in our body.Carbohydrate: any organic compound that Carbohydrate: any organic compound that is made of carbon, hydrogen & oxygen & is made of carbon, hydrogen & oxygen & that provides nutrients to the cells of living that provides nutrients to the cells of living things.things.

ProteinsProteinsA protein is a biological polymer made of A protein is a biological polymer made of bonded amino acids.bonded amino acids.

An amino acid is any of 20 different An amino acid is any of 20 different naturally occurring organic molecules that naturally occurring organic molecules that combine to form proteins.combine to form proteins.

Amino acids (there are 20) are made C, H, Amino acids (there are 20) are made C, H, O, & N.O, & N.

How they combine determines the protein.How they combine determines the protein.

Proteins are long chains of amino acids.Proteins are long chains of amino acids.

DNA is a polymer w/complex DNA is a polymer w/complex structurestructure

DNA determines entire genetic make DNA determines entire genetic make up & is made of C, H, O, N & P.up & is made of C, H, O, N & P.

DNA has the shape of a twisted DNA has the shape of a twisted ladder known as a ladder known as a double helix.double helix.

Every cell in your body has a copy of Every cell in your body has a copy of your genetic make up.your genetic make up.