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Chapter 5Chapter 5

Atoms, Molecules, and Ions Atoms, Molecules, and Ions

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HistoryHistory GreeksGreeks Democritus and Leucippus - atomosDemocritus and Leucippus - atomos Aristotle- 4 elements.Aristotle- 4 elements. Alchemy-experimentationAlchemy-experimentation 1660 - Robert Boyle- experimental 1660 - Robert Boyle- experimental

definition of element.definition of element. Lavoisier- Father of modern chemistry.Lavoisier- Father of modern chemistry. He wrote the book.He wrote the book.

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Conservation of MassConservation of Mass

In any chemical reaction the total In any chemical reaction the total mass of the reactants will equal the mass of the reactants will equal the total mass of the productstotal mass of the products

36.04 g Reactants 36.04 g Products36.04 g Reactants 36.04 g Products

2H2H22 + O + O22 2H 2H22OO

4.04g + 32.00g = 36.04g4.04g + 32.00g = 36.04g

LawsLaws

Law of Definite Proportion-Law of Definite Proportion- The law stating that a pure substance, The law stating that a pure substance,

e.g. He.g. H22O, will always have the same O, will always have the same percent by weightpercent by weight, e.g. 11.2% H  and , e.g. 11.2% H  and 88.8% O.88.8% O.

elements will combine in specific elements will combine in specific ratios by mass.ratios by mass.

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Law of Definite ProportionsLaw of Definite Proportions

HH220 H 2 x 1.01g = 2.02g0 H 2 x 1.01g = 2.02g

O 1 x 16.00g = 16.00gO 1 x 16.00g = 16.00g

18.02g18.02g

2.02g H / 18.02 g H2.02g H / 18.02 g H22O = 0.11 x 100 = 11%O = 0.11 x 100 = 11%

16.00g H / 18.02 g H16.00g H / 18.02 g H22O = 0.88 x 100 = 88 %O = 0.88 x 100 = 88 %

What are the proportions in a COWhat are the proportions in a CO22 molecule? molecule?

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Law of Multiple ProportionsLaw of Multiple ProportionsIn chemistry, the law of multiple proportions is sometimes called Dalton's Law after its discoverer, the English chemist John Dalton.

The law is:

If two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers.

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For example carbon oxide: CO and CO2

100 grams of carbon may react with 133 grams of oxygen to produce carbon monoxide (CO)

100 grams of carbon may react with 266 grams of oxygen to produce carbon dioxide (CO2)

The ratio of the masses of oxygen that can react with 100 grams of carbon is 266:133 ≈ 2:1, a ratio of small whole numbers.

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What?!What?! Compare Water HCompare Water H22O and Hydrogen Peroxide O and Hydrogen Peroxide

HH22OO22

HH22O - H 2 x 1.01g = 2.02 gO - H 2 x 1.01g = 2.02 g

O 1 x 16.00g = 16.00 gO 1 x 16.00g = 16.00 g

16.00 g Oxygen / 2.02 g Hydrogen = 16.00 g Oxygen / 2.02 g Hydrogen =

8gO/1gH8gO/1gH

Water has 8 g of oxygen per 1 g of hydrogen.Water has 8 g of oxygen per 1 g of hydrogen.

Law of Multiple ProportionsLaw of Multiple Proportions

HH22OO22 – H 2 x 1.01g = 2.02g – H 2 x 1.01g = 2.02g

O 2 x 16.00g = 32.00gO 2 x 16.00g = 32.00g

32.00 g Oxygen / 2.02g Hydrogen = 32.00 g Oxygen / 2.02g Hydrogen =

16gO/1gH16gO/1gH Hydrogen peroxide has 16 g of oxygen per g of Hydrogen peroxide has 16 g of oxygen per g of

hydrogen.hydrogen. Compare the 2 samplesCompare the 2 samples 16g 16g H2O2 H2O2 / 8g / 8g H2H2 = 2 / 1 ratio = 2 / 1 ratio Small whole number ratios.Small whole number ratios.

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Dalton’s Atomic TheoryDalton’s Atomic Theory1)1) Elements are made up of atomsElements are made up of atoms

2)2) Atoms of each element are identical. Atoms of each element are identical. Atoms of different elements are different.Atoms of different elements are different.

3)3) Compounds are formed when atoms Compounds are formed when atoms combine. Each compound has a specific combine. Each compound has a specific number and kinds of atom.number and kinds of atom.

4)4) Chemical reactions are rearrangement of Chemical reactions are rearrangement of atoms. Atoms are not created or atoms. Atoms are not created or destroyed.destroyed.

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Experiments to determine what Experiments to determine what an atom wasan atom was

J. J. Thomson- used Cathode ray tubesJ. J. Thomson- used Cathode ray tubes

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Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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Passing an electric current makes a beam Passing an electric current makes a beam appear to move from the negative to the appear to move from the negative to the positive end.positive end.

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field By adding an electric field

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Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field, he found that By adding an electric field, he found that the moving pieces were negative the moving pieces were negative

+

-

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Thomsom’s ModelThomsom’s Model Found the electron.Found the electron. Couldn’t find positive Couldn’t find positive

(for a while). (for a while). Said the atom was like Said the atom was like

plum pudding.plum pudding. A bunch of positive A bunch of positive

stuff, with the stuff, with the electrons able to be electrons able to be removed. removed.

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Rutherford’s ExperimentRutherford’s Experiment Used uranium to produce alpha particles.Used uranium to produce alpha particles. Aimed alpha particles at gold foil by Aimed alpha particles at gold foil by

drilling hole in lead block.drilling hole in lead block. Since the mass is evenly distributed in Since the mass is evenly distributed in

gold atoms alpha particles should go gold atoms alpha particles should go straight through.straight through.

Used gold foil because it could be made Used gold foil because it could be made atoms thin.atoms thin.

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Lead block

Uranium

Gold Foil

Florescent Screen

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What he expected

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Because

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Because, he thought the mass was evenly distributed in the atom.

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What he got

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How he explained it

+

Atom is mostly emptyAtom is mostly empty Small dense,Small dense,

positive piecepositive pieceat center.at center.

Alpha particlesAlpha particlesare deflected byare deflected by it if it if they get closethey get close enough. enough.

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+

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Modern ViewModern View The atom is mostly The atom is mostly

empty space.empty space. Two regionsTwo regions Nucleus- protons Nucleus- protons

and neutrons.and neutrons. Electron cloud- Electron cloud-

region where you region where you might find an might find an electron.electron.

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Sub-atomic ParticlesSub-atomic Particles Z - atomic number = number of protons Z - atomic number = number of protons

determines type of atom.determines type of atom. A - mass number = number of protons + A - mass number = number of protons +

neutrons.neutrons. Number of protons = number of electrons if Number of protons = number of electrons if

neutral.neutral.

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SymbolsSymbols

XA

Z

Na23

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Mass #

Atomic#

(p+ and n0)

(p+)

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Periodic TablePeriodic Table

Click Link

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MetalsMetals ConductorsConductors Lose electronsLose electrons Malleable and ductileMalleable and ductile

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NonmetalsNonmetals BrittleBrittle Gain electronsGain electrons Covalent bondsCovalent bonds

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Semi-metals or MetalloidsSemi-metals or Metalloids

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Alkali Metals

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Alkaline Earth Metals

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Halogens

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Transition metals

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Noble Gases

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Inner Transition Metals

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+1+2 -1-2-3

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IonsIons Atoms or groups of atoms with a charge.Atoms or groups of atoms with a charge. Cations- positive ions - metals losing Cations- positive ions - metals losing

electrons(s).electrons(s). Anions- negative ions - nometals gaining Anions- negative ions - nometals gaining

electron(s).electron(s). Ionic bonding- held together by the Ionic bonding- held together by the

opposite charges.opposite charges. Ionic solids are called salts.Ionic solids are called salts.

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Polyatomic IonsPolyatomic Ions Groups of atoms that have a charge.Groups of atoms that have a charge. No, you don’t have to memorize them.No, you don’t have to memorize them. List on page 97 or on the back of your List on page 97 or on the back of your

periodic table.periodic table.

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Naming compoundsNaming compounds Two typesTwo types IonicIonic - metal and non metal or polyatomics. - metal and non metal or polyatomics. If the metal is in the 1If the metal is in the 1stst or 2 or 2ndnd column column

(representative element). NO (roman numeral) in (representative element). NO (roman numeral) in the namethe name

If the metal is a transition metal a (roman If the metal is a transition metal a (roman numeral) may be needed (check your periodic numeral) may be needed (check your periodic table)table)

CovalentCovalent- we will just learn the rules for 2 non-- we will just learn the rules for 2 non-metals.metals.

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Ionic compoundsIonic compounds If the cation is monoatomic- Name the metal (cation) If the cation is monoatomic- Name the metal (cation)

just write the name.just write the name.Mg Mg 2+2+ MagnesiumMagnesium

If the cation is polyatomic- name it.If the cation is polyatomic- name it.

NHNH44++ AmmoniumAmmonium

If the anion is monoatomic- name it but change the If the anion is monoatomic- name it but change the ending to ending to –ide.–ide.ClCl1-1- ChlorChlorideide

If the anion is polyatomic- just name itIf the anion is polyatomic- just name it

POPO44 3-3- PhosphatePhosphate Practice.Practice.

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Ionic CompoundsIonic 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 Two types Two types

– Binary ionic – 2 elements (cation + anion)Binary ionic – 2 elements (cation + anion)– Ternary ionic – 3 elements Ternary ionic – 3 elements – (cation + Polyatomic ion)(cation + Polyatomic ion)

CaSCaS KK22SS

AlPOAlPO44 KK22SOSO44

FeSFeS CoICoI33

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Ionic CompoundsIonic Compounds FeFe22(C(C22OO44))

MgOMgO MnOMnO

KMnOKMnO44

NHNH44NONO33

HgHg22ClCl22

CrCr22OO33

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Ionic CompoundsIonic Compounds KClOKClO44

NaClONaClO33

YBrOYBrO22

Cr(ClO)Cr(ClO)66

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Writing FormulasWriting Formulas Two sets of rules, ionic and covalentTwo sets of rules, ionic and covalent To decide which to use, decide what the To decide which to use, decide what the

first wordfirst word or elementor element is. is. If it is a metal or polyatomic use If it is a metal or polyatomic use ionicionic.. If it is a non-metal use If it is a non-metal use covalentcovalent..

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Ionic FormulasIonic Formulas Charges must add up to zero.Charges must add up to zero. Get charges from table, name of metal ion, Get charges from table, name of metal ion,

or memorized from the list.or memorized from the list. Use parenthesis to indicate multiple Use parenthesis to indicate multiple

polyatomics.polyatomics.

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Ionic FormulasIonic 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

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Ionic FormulasIonic 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

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Ionic FormulasIonic 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

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Ionic CompoundsIonic Compounds 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

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Chemical BondsChemical Bonds The forces that hold atoms together.The forces that hold atoms together. Covalent bonding - sharing electrons.Covalent bonding - sharing electrons. Makes molecules.Makes molecules. 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.

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H

H

H H

H

HC C

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

Ball and stick.Ball and stick.

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Binary Molecular CompoundsBinary Molecular Compounds Two words, with prefixes.Two words, with prefixes. Prefixes tell you how many atoms.Prefixes tell you how many atoms. 1-mono, 2-di, 3-tri, 4-tetr(a), 5-pent(a), 1-mono, 2-di, 3-tri, 4-tetr(a), 5-pent(a),

6-hex(a), 7-hept(a), 8 oct(a),9-non(a), 10-dec(a)6-hex(a), 7-hept(a), 8 oct(a),9-non(a), 10-dec(a)

Name : PName : P44ClCl77

First element whole name with the appropriate prefix, except First element whole name with the appropriate prefix, except monomono PP44 = = tetratetraphosphorusphosphorus

Second element, Second element, -ide -ide ending with appropriate prefixending with appropriate prefix

ClCl77 == heptaheptachlorchlorideide

PracticePractice

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COCO22

CO CO CClCCl44

NN22OO44

XeFXeF66

NN44OO44

PP22OO1010

Naming Covalent CompoundsNaming Covalent Compounds

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Binary Molecular (Covalent) Binary Molecular (Covalent) CompoundsCompounds

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

Sulfur dioxideSulfur dioxide diflourine monoxidediflourine monoxide nitrogen trichloridenitrogen trichloride diphosphorus pentoxidediphosphorus pentoxide

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More Names and formulasMore Names and formulas

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AcidsAcids Substances that produce hydrogen (HSubstances that produce hydrogen (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: Oxyacids – oxygen in the formulaOxyacids – oxygen in the formula Non-oxyacids – no oxygen in the formulaNon-oxyacids – no oxygen in the formula

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Naming Acids

Hydrogen _______ide becomes hydro____ic acid

Hydrogen_______ate becomes _________ic acid

Hydrogen_______ite becomes _______ous acid

Hydrogen always #1 on periodic table

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Using naming acids table

Name : HCl from the periodic table ionic name is hydrogen chloride so use:

Hydrogen _______ide becomes hydro______ic acidchlor chlor

Transfer word root from one side to the other

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Using naming acids table

Write the formula for sulphuric acid: use

Hydrogen_______ate becomes _________ic acidsulphursulph

Ionic name is hydrogen sulphate

H+ SO4 2-

So acid formula is H2SO4

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Naming acidsNaming acids If the formula has oxygen in it(oxyacid)If the formula has oxygen in it(oxyacid) 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

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Naming acidsNaming acids If the acid doesn’t have If the acid doesn’t have

oxygen(nonoxyacid)oxygen(nonoxyacid) add the prefix hydro-add the prefix hydro- change the suffix -ide to -ic acidchange the suffix -ide to -ic acid HClHCl HH22SS

HCNHCN

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Formulas for acidsFormulas for acids Backwards from names.Backwards from names. If it has hydro- in the name it has no oxygenIf it has hydro- in the name it has no oxygen 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 balance Write anion and add enough H to balance

the charges.the charges.

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Formulas for acidsFormulas for acids hydrofluoric acidhydrofluoric acid chromic acidchromic acid carbonic acidcarbonic acid hydrophosphoric acidhydrophosphoric acid fluorous acidfluorous acid perchloric acidperchloric acid phosphorous acid phosphorous acid

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

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

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

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

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HydratesHydrates In the formula you put a dot and then write In the formula you put a dot and then write

the number of molecules.the number of molecules. Calcium chloride dihydrate = CaClCalcium chloride dihydrate = CaCl2222 Chromium (III) nitrate hexahydrate = Chromium (III) nitrate hexahydrate =

Cr(NOCr(NO33))33 6H 6H22O O

Simulation of a Hydrate

Hydrate Nomenclature Practice

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compounds

binary ternary

molecular ionic acids

molecules

hydrates

formula unit

All nonmetals Metal or hydrogen and nonmetalsor Polyatomics

trapped water