AP Notes Chapter 2 Molecules, Ions and Their Compounds.

AP Notes Chapter 2 AP Notes Chapter 2

Molecules, Ions and Their Compounds Molecules, Ions and Their Compounds

Chemical CompoundsChemical Compounds Chemical compounds result from the Chemical compounds result from the

joining together of atomsjoining together of atoms Chemical Bonds are the forces that hold Chemical Bonds are the forces that hold

atoms together.atoms together. Chemical formulas are used to describe Chemical formulas are used to describe

the number and kind of atoms in a the number and kind of atoms in a compoundcompound There are two major types of There are two major types of compounds that differ mostly by the compounds that differ mostly by the way the atoms hold on to each other way the atoms hold on to each other or the type of bond.or the type of bond.

•Ionic compound are held together with an Ionic compound are held together with an Ionic bond joining metal ions and non metal Ionic bond joining metal ions and non metal ions ions

•Transfer of electrons cause the formation of Transfer of electrons cause the formation of ions or charged particlesions or charged particles

Ionic CompoundsIonic Compounds

Ions & Ionic CompoundsIons & Ionic Compounds Atoms or groups of atoms with a charge.Atoms or groups of atoms with a charge. Cations- positive ions - get by losing Cations- positive ions - get by losing

electrons(s). Metallicelectrons(s). Metallic Anions- negative ions - get by gaining Anions- negative ions - get by gaining

electron(s). Nonmetallicelectron(s). Nonmetallic It is these opposite charges that define It is these opposite charges that define

an ionic compound and an ionic bondan ionic compound and an ionic bond Solid Ionic compounds are called salts.Solid Ionic compounds are called salts.

+1+2 -1-2-3

Ionic CompoundsIonic Compounds Law of Definite Proportion-Law of Definite Proportion- compounds have a constant composition. compounds have a constant composition. Ions react in specific ratios by mass and charge.Ions react in specific ratios by mass and charge. Ionic compounds do not have a chargeIonic compounds do not have a charge Positive and negative charges balance Positive and negative charges balance Ions exist in small whole number ratios.Ions exist in small whole number ratios. Get charges from table, name of metal ion, or memorized from the Get charges from table, name of metal ion, or memorized from the

list.list. Use parenthesis to indicate multiple polyatomics.Use parenthesis to indicate multiple polyatomics.

Naming Ionic CompoundsNaming Ionic Compounds Cation is wrtiten first in name and formula. Cation is wrtiten first in name and formula. If the cation is monoatomic- Name the If the cation is monoatomic- Name the

metal (cation) just write the name.metal (cation) just write the name. If the cation is polyatomic- name it.If the cation is polyatomic- name it. THEN If the anion is monoatomic- name it THEN If the anion is monoatomic- name it

but change the ending to but change the ending to –ide.–ide. If the anion is poly atomic- just name itIf the anion is poly atomic- just name it Practice Ion names and formula w/chargePractice Ion names and formula w/charge

Naming Ionic CompoundsNaming Ionic Compounds Have to know what ions they formHave to know what ions they form off table, polyatomic, or figure it outoff table, polyatomic, or figure it out CaSCaS KK22SS

AlPOAlPO44 KK22SOSO44

FeSFeS CoICoI33

Calcium sulfide

Potassium sulfide

Aluminum phosphate

Potassium sulfate

Iron II sulfide or Ferrous sulfide

Cobalt III iodide or Cobaltic iodide

Naming Ionic CompoundsNaming Ionic Compounds FeFe22(C(C22OO44))

MgOMgO MnOMnO

KMnOKMnO44

NHNH44NONO33

HgHg22ClCl22

CrCr22OO33

Writing Ionic FormulasWriting Ionic Formulas

Sodium nitrideSodium nitride sodium- Na is always +1sodium- Na is always +1 Nitride - ide tells you it comes from the Nitride - ide tells you it comes from the

tabletable nitride is Nnitride is N-3-3 Doesn’t add up to zero.Doesn’t add up to zero.

Na+1 N-3

Writing Ionic FormulasWriting Ionic Formulas Sodium nitrideSodium nitride sodium- Na is always +1sodium- Na is always +1 nitride - ide tells you it comes from the tablenitride - ide tells you it comes from the table nitride is Nnitride is N-3-3 Doesn’t add up to zeroDoesn’t add up to zero Need 3 NaNeed 3 Na

Na+1 N-3 Na3N

Ionic Compound FormulasIonic Compound Formulas Sodium sulfiteSodium sulfite calcium iodidecalcium iodide Lead (II) oxide Lead (II) oxide Lead (IV) oxideLead (IV) oxide Mercury (I) sulfideMercury (I) sulfide Barium chromateBarium chromate Aluminum hydrogen sulfateAluminum hydrogen sulfate Cerium (IV) nitriteCerium (IV) nitrite

Na2S

CaI2

PbOPb2O4 or PbO2

Hg2S

BaCrO4

Al(HSO4)3

Ce(NO3)4

Covalent CompoundsCovalent Compounds Composed of MoleculesComposed of Molecules Law of Multiple Proportions-Law of Multiple Proportions- When two When two

elements form more than one compound, elements form more than one compound, the ratios of the masses of the second the ratios of the masses of the second element that combine with one gram of the element that combine with one gram of the first can be reduced to small whole first can be reduced to small whole numbers.numbers.

Chemical formula- the number and type of Chemical formula- the number and type of atoms in a molecule. atoms in a molecule.

CC22HH66 - 2 carbon atoms, 6 hydrogen atoms - 2 carbon atoms, 6 hydrogen atoms Structural formula shows the connections, Structural formula shows the connections,

but not necessarily the shape.but not necessarily the shape.

Molecules differ by the number and Molecules differ by the number and kind of elements that make them up kind of elements that make them up

Speculate on the formula of two oxides Speculate on the formula of two oxides of carbon and oxygenof carbon and oxygen Carbon monoxide =Carbon monoxide = Carbon dioxide =Carbon dioxide =

Show that these compounds follow the Show that these compounds follow the law of multiple proportion.law of multiple proportion.

Sometimes formula is not enough to Sometimes formula is not enough to get an adequate picture of a compoundget an adequate picture of a compound

CO

CO2

H

H

H H

H

HC C

There are also other models that There are also other models that attempt to show three dimensional attempt to show three dimensional shape.shape.

Ball and stick.Ball and stick.

Ball and stick.Ball and stick.

Covalent compoundsCovalent compounds Two words, with prefixes.Two words, with prefixes. Prefixes tell you how many.Prefixes tell you how many. mono, di, tri, tetra, penta, hexa, mono, di, tri, tetra, penta, hexa,

septa, nona, decasepta, nona, deca First element whole name with the First element whole name with the

appropriate prefix, except mono.appropriate prefix, except mono. Second element, Second element, -ide -ide ending with ending with

appropriate prefix.appropriate prefix. PracticePractice

Naming Covalent Naming Covalent CompoundsCompounds Two words, with prefixesTwo words, with prefixes

Prefixes tell you how many.Prefixes tell you how many. mono, di, tri, tetra, penta, hexa, mono, di, tri, tetra, penta, hexa,

septa, nona, decasepta, nona, deca First element whole name with the First element whole name with the

appropriate prefix, except monoappropriate prefix, except mono Second element, Second element, -ide -ide ending with ending with

appropriate prefixappropriate prefix PracticePractice

COCO22

CO CO CClCCl44

NN22OO44

XeFXeF66

NN44OO44

PP22OO1010

Naming Covalent Naming Covalent CompoundsCompounds

Covalent compoundsCovalent compounds

The name tells you how to write the The name tells you how to write the formulaformula

Sulfur dioxideSulfur dioxide difluorine monoxidedifluorine monoxide nitrogen trichloridenitrogen trichloride diphosphorus pentoxidediphosphorus pentoxide

Summary for Writing Summary for Writing Formulas and Names of Formulas and Names of

Compounds Compounds Two sets of rules, ionic and covalentTwo sets of rules, ionic and covalent To decide which to use, decide what To decide which to use, decide what

the first word is.the first word is. If is a metal or polyatomic use ionic.If is a metal or polyatomic use ionic. If it is a non-metal use covalent.If it is a non-metal use covalent.

AcidsAcids

Substances that produce HSubstances that produce H++ ions ions when dissolved in water.when dissolved in water.

All acids begin with H.All acids begin with H. Two types of acids: Two types of acids: OxyacidsOxyacids Non-oxyacidsNon-oxyacids

Naming acidsNaming acids

If the formula has oxygen in itIf the formula has oxygen in it write the name of the anion, but change write the name of the anion, but change

ate to -ic acidate to -ic acid ite to -ous acidite to -ous acid

Watch out for sulfWatch out for sulfururic and sulfic and sulfururousous HH22CrOCrO44

HMnOHMnO44

HNOHNO22

Naming acidsNaming acids

If the acid doesn’t have oxygenIf the acid doesn’t have oxygen add the prefix hydro-add the prefix hydro- change the suffix -ide to -ic acidchange the suffix -ide to -ic acid HClHCl HH22SS

HCNHCN

Formulas for acidsFormulas for acids

Backwards from names.Backwards from names. If it has hydro- in the name it has no If it has hydro- in the name it has no

oxygenoxygen Anion ends in -ideAnion ends in -ide No hydro, anion ends in -ate or -iteNo hydro, anion ends in -ate or -ite Write anion and add enough H to Write anion and add enough H to

balance the charges.balance the charges.

Formulas for acidsFormulas for acids hydrofluoric acidhydrofluoric acid dichromic aciddichromic acid carbonic acidcarbonic acid hydrophosphoric acidhydrophosphoric acid hypofluorous acidhypofluorous acid perchloric acidperchloric acid phosphorous acid phosphorous acid

Percent Percent CompositionComposition Percent of each element a compound is Percent of each element a compound is

composed of.composed of. Find the mass of each element, divide by Find the mass of each element, divide by

the total mass, multiply by a 100.the total mass, multiply by a 100. Easiest if you use a mole of the Easiest if you use a mole of the

compound.compound. Find the percent composition of CHFind the percent composition of CH44

AlAl22(Cr(Cr22OO77))33

CaSOCaSO44 · 2H · 2H22OO

Working Working backwardsbackwards From percent composition, you can From percent composition, you can

determine the empirical formula.determine the empirical formula. Empirical FormulaEmpirical Formula the lowest ratio of the lowest ratio of

atoms in a molecule.atoms in a molecule. Based on mole ratios.Based on mole ratios. A sample is 59.53% C, 5.38%H, A sample is 59.53% C, 5.38%H,

10.68%N, and 24.40%O what is its 10.68%N, and 24.40%O what is its empirical formula.empirical formula.

Sample ProblemSample Problem

A 0.2000 gram sample of a A 0.2000 gram sample of a compound (vitamin C) composed of compound (vitamin C) composed of only C, H, and O is burned only C, H, and O is burned completely with excess Ocompletely with excess O22 . 0.2998 g . 0.2998 g

of COof CO22 and 0.0819 g of H and 0.0819 g of H22O are O are

produced. What is the empirical produced. What is the empirical formula?formula?

Empirical To Molecular Empirical To Molecular FormulasFormulas

Empirical is lowest ratio.Empirical is lowest ratio. Molecular is actual molecule.Molecular is actual molecule. Need Molar mass.Need Molar mass. Ratio of empirical to molar mass will Ratio of empirical to molar mass will

tell you the molecular formula.tell you the molecular formula. Must be a whole number because...Must be a whole number because...

Sample ProblemSample Problem A compound is made of only sulfur A compound is made of only sulfur

and oxygen. It is 69.6% S by mass. and oxygen. It is 69.6% S by mass. Its molar mass is 184 g/mol. What is Its molar mass is 184 g/mol. What is its formula?its formula?

HydratesHydrates Some salts trap water crystals when Some salts trap water crystals when

they form crystals.they form crystals. These are hydrates.These are hydrates. Both the name and the formula needs Both the name and the formula needs

to indicate how many water molecules to indicate how many water molecules are trapped.are trapped.

In the name we add the word hydrate In the name we add the word hydrate with a prefix that tells us how many with a prefix that tells us how many water molecules. water molecules.

HydrateHydratess In the formula you put a dot and then In the formula you put a dot and then

write the number of molecules.write the number of molecules. Calcium chloride dihydrateCalcium chloride dihydrate

Chromium (III) nitrate hexahydrateChromium (III) nitrate hexahydrateCaClCaCl2222

Cr(NOCr(NO33))33 6H 6H22OO