Unit # 4Unit # 4

Atomic TheoryAtomic Theory

HistoryHistoryGreeksGreeks Democritus (460-370BC)Democritus (460-370BC)

– – Matter is made of atoms.Matter is made of atoms.- Different kinds of shapes and sizes- Different kinds of shapes and sizes

Aristotle ( 364 -322 BC)Aristotle ( 364 -322 BC)- didn’t believe of atoms.didn’t believe of atoms.- - - Matter is made of earth, fire, Matter is made of earth, fire,

air, and waterair, and water..

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

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

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

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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

+-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field By adding an electric field

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

+

-

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.

Millikan’s ExperimentMillikan’s Experiment

Oil

Atomizer

Oil droplets

Telescope

-

+

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.

Lead block

Uranium

Gold Foil

Florescent Screen

What he expected

Because

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

What he got

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.

Inside the Gold atomInside the Gold atom

+

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.

Chadwick 1932Chadwick 1932 James Chadwick proves the existence of James Chadwick proves the existence of

neutronsneutrons He fired protons at Lithium nuclei, splitting He fired protons at Lithium nuclei, splitting

them into helium nuclei and releasing them into helium nuclei and releasing energy.energy.

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. N= A-ZN= A-Z Number of protons = number of electrons if Number of protons = number of electrons if

neutral.neutral.

SymbolsSymbols

XA

Z

Na23

11

How Atoms DifferHow Atoms Differ Atomic number = Atomic number =

number of protonsnumber of protons Atomic number = Atomic number =

number of electrons.number of electrons.

Number of Neutrons= Number of Neutrons= mass # - Protons #mass # - Protons #

Problem:Problem:

ElemeElementnt

AtomiAtomic #c #

ElectrElectronsons

NeutrNeutronsons

NN

OO

ZnZn

HomeworkHomework1.1. How many electrons and protons are in How many electrons and protons are in

each atom?each atom?

RadonRadon ; Magnesium; Magnesium

2.2. An atom contains 66 electrons. Which An atom contains 66 electrons. Which element is it?element is it?

3.3. An atom of an element contains 14 An atom of an element contains 14 protons. Which element is it?protons. Which element is it?

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.

H

H

H H

H

HC C

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

Ball and stick.Ball and stick.

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

Polyatomic IonsPolyatomic Ions Groups of atoms that have a charge.Groups of atoms that have a charge. Yes, you have to memorize them.Yes, you have to memorize them. List on page 65List on page 65

Periodic TablePeriodic Table

MetalsMetals ConductorsConductors Lose electronsLose electrons Malleable and ductileMalleable and ductile

NonmetalsNonmetals BrittleBrittle Gain electronsGain electrons Covalent bondsCovalent bonds

Semi-metals or MetalloidsSemi-metals or Metalloids

Alkali Metals

Alkaline Earth Metals

Halogens

Transition metals

Noble Gases

Inner Transition Metals

+1+2 -1-2-3

Naming compoundsNaming compounds Two typesTwo types IonicIonic - metal and non metal or polyatomics. - metal and non metal or polyatomics. CovalentCovalent- we will just learn the rules for 2 - we will just learn the rules for 2

non-metals.non-metals.

Ionic compoundsIonic compounds 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. If the anion is monoatomic- name it but If the anion is monoatomic- name it but

change the ending to change the ending to –ide.–ide. If the anion is poly atomic- just name itIf the anion is poly atomic- just name it Practice.Practice.

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, septa, nona, mono, di, tri, tetra, penta, hexa, septa, nona,

decadeca 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

More NamingMore Naming

Ionic compoundsIonic compounds 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 itIf the cation is polyatomic- name it If the anion is monoatomic- name it but If the anion is monoatomic- name it but

change the ending to change the ending to -ide-ide If the anion is poly atomic- just name itIf the anion is poly atomic- just name it practicepractice

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 CaSCaS KK22SS

AlPOAlPO44

KK22SOSO44

FeSFeS CoICoI33

Ionic CompoundsIonic Compounds FeFe22(C(C22OO44))

MgOMgO MnOMnO

KMnOKMnO44

NHNH44NONO33

HgHg22ClCl22

CrCr22OO33

Ionic CompoundsIonic Compounds KClOKClO44

NaClONaClO33

YBrOYBrO22

Cr(ClO)Cr(ClO)66

Naming Covalent CompoundsNaming Covalent Compounds Two words, with prefixesTwo words, with prefixes Prefixes tell you how many.Prefixes tell you how many. mono, di, tri, tetra, penta, hexa, septa, nona, mono, di, tri, tetra, penta, hexa, septa, nona,

decadeca 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 appropriate ending with appropriate

prefixprefix PracticePractice

COCO22

CO CO CClCCl44

NN22OO44

XeFXeF66

NN44OO44

PP22OO1010

Naming Covalent CompoundsNaming Covalent Compounds

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 word is.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.

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.

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

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

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

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

Covalent compoundsCovalent compounds The name tells you how to write the The name tells you how to write the

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

More Names and formulasMore Names and formulas

AcidsAcids Substances that produce HSubstances that produce H++ ions when ions when

dissolved in water.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 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.

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

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.

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