Chapter 2 Atoms, Molecules, and Ions History n Greeks n Democritus and Leucippus - atomos n Aristotle- elements n Alchemy n 1660 - Robert Boyle- experimental.
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Chapter 2Chapter 2
Atoms, Molecules, and Ions Atoms, Molecules, and Ions
HistoryHistory GreeksGreeks Democritus and Leucippus - atomosDemocritus and Leucippus - atomos Aristotle- elementsAristotle- elements AlchemyAlchemy 1660 - Robert Boyle- experimental 1660 - Robert Boyle- experimental
definition of element.definition of element. Lavoisier- Father of modern chemistryLavoisier- Father of modern chemistry He wrote the book- used measurementHe wrote the book- used measurement
LawsLaws Conservation of MassConservation of Mass Law of Definite Proportion-Law of Definite Proportion- compounds compounds
have a constant composition by mass.have a constant composition by mass. They react in specific ratios by mass.They react in specific ratios by mass. Multiple Proportions-Multiple Proportions- When two elements When two elements
form more than one compound, the ratios of form more than one compound, the ratios of the masses of the second element that the masses of the second element that combine with one gram of the first can be combine with one gram of the first can be reduced to small whole numbers.reduced to small whole numbers.
What?!What?! Water has 8 g of oxygen per g of hydrogen.Water has 8 g of oxygen per g of hydrogen. Hydrogen peroxide has 16 g of oxygen per Hydrogen peroxide has 16 g of oxygen per
g of hydrogen.g of hydrogen. 16/8 = 2/116/8 = 2/1 Small whole number ratiosSmall whole number ratios
Example of Law Of Multiple Example of Law Of Multiple ProportionsProportions
Mercury has two oxides. One is 96.2 % Mercury has two oxides. One is 96.2 % mercury by mass, the other is 92.6 % mercury by mass, the other is 92.6 % mercury by mass.mercury by mass.
Show that these compounds follow the law Show that these compounds follow the law of multiple proportion.of multiple proportion.
Speculate on the formula of the two oxides.Speculate on the formula of the two oxides.
Your TurnYour Turn Nitrogen and oxygen form two compounds.Nitrogen and oxygen form two compounds.
Show that they follow the law of multiple Show that they follow the law of multiple proportionsproportions
Amount NAmount N Amount OAmount O
Compound ACompound A 1.206 g1.206 g 2.755 g2.755 g
Compound BCompound B 1.651g1.651g 4.714 g4.714 g
Dalton’s Atomic TheoryDalton’s Atomic Theory 1. Elements are made up of atoms1. Elements are made up of atoms 2. Atoms of each element are identical. 2. Atoms of each element are identical.
Atoms of different elements are different.Atoms of different elements are different. 3. Compounds are formed when atoms 3. 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. Chemical reactions are rearrangement of 4. Chemical reactions are rearrangement of atoms. Atoms are not created or destroyed.atoms. Atoms are not created or destroyed.
Gay-Lussac- under the same conditions of Gay-Lussac- under the same conditions of temperature and pressure, compounds temperature and pressure, compounds always react in whole number ratios by always react in whole number ratios by volume.volume.
Avagadro- interpreted that to mean Avagadro- interpreted that to mean at the same temperature and pressure, equal at the same temperature and pressure, equal
volumes of gas contain the same number of volumes of gas contain the same number of particlesparticles
(called Avagadro’s hypothesis)(called Avagadro’s hypothesis)
A Helpful ObservationA Helpful Observation
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
+-
Thomson’s ExperimentThomson’s Experiment
Voltage source
+-
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 endpositive end
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 endpositive end
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 endpositive end
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 endpositive 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 By adding an electric field
+
-
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 By adding an electric field
+
-
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 By adding an electric field
+
-
Voltage source
Thomson’s ExperimentThomson’s Experiment
By adding an electric field he found that the By adding an electric field he found that the moving pieces were negative moving pieces were negative
+
-
Thomsom’s ModelThomsom’s Model Found the electronFound the electron Couldn’t find Couldn’t find
positive (for a while) positive (for a while) Said the atom was Said the atom was
like plum puddinglike 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
Atomizer
Microscope
-
+
Oil
Millikan’s ExperimentMillikan’s Experiment
Oil
Atomizer
Microscope
-
+
Oil droplets
Millikan’s ExperimentMillikan’s Experiment
X-rays
X-rays give some drops a charge by knocking offelectrons
Millikan’s ExperimentMillikan’s Experiment
+
Millikan’s ExperimentMillikan’s Experiment
They put an electric charge on the plates
++
--
Millikan’s ExperimentMillikan’s Experiment
Some drops would hover
++
--
Millikan’s ExperimentMillikan’s Experiment
+
+ + + + + + +
- - - - - - -
Millikan’s ExperimentMillikan’s Experiment
Measure the drop and find volume from 4/3πr3
Find mass from M = D x V
++
--
Millikan’s ExperimentMillikan’s Experiment
From the mass of the drop and the charge on the plates, he calculated the charge on an electron
++
--
RadioactivityRadioactivity Discovered by accidentDiscovered by accident BequerelBequerel Three types Three types
– alpha- helium nucleus (+2 charge, large alpha- helium nucleus (+2 charge, large mass)mass)
– beta- high speed electronbeta- high speed electron
– gamma- high energy lightgamma- high energy light
Rutherford’s ExperimentRutherford’s Experiment Used uranium to produce alpha particlesUsed uranium to produce alpha particles Aimed alpha particles at gold foil by Aimed alpha particles at gold foil by
drilling hole in lead blockdrilling 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 thinatoms 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 piece at centerat center
Alpha particles Alpha particles are deflected byare deflected by it if it if they get closethey get close enough enough
+
Modern ViewModern View The atom is mostly The atom is mostly
empty spaceempty space Two regionsTwo regions Nucleus- protons and Nucleus- protons and
neutronsneutrons Electron cloud- region Electron cloud- region
where you have a where you have a chance of finding an chance of finding an electronelectron
Sub-atomic ParticlesSub-atomic Particles Z - atomic number = number of protons Z - atomic number = number of protons
determines type of atomdetermines type of atom A - mass number = number of protons + A - mass number = number of protons +
neutronsneutrons Number of protons = number of electrons if Number of protons = number of electrons if
neutralneutral
SymbolsSymbols
XA
Z
Na23
11
Chemical BondsChemical Bonds The forces that hold atoms togetherThe forces that hold atoms together Covalent bonding - sharing electronsCovalent bonding - sharing electrons makes moleculesmakes 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
Structural FormulaStructural Formula
There are also other model that attempt to There are also other model that attempt to show three dimensional shapeshow three dimensional shape
Ball and stick (see the models in room)Ball and stick (see the models in room)
Space Filling Space Filling
IonsIons Atoms or groups of atoms with a chargeAtoms 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 chargesopposite charges Ionic solids are called saltsIonic solids are called salts
Polyatomic Ions Polyatomic Ions Groups of atoms that have a chargeGroups 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-metalsnon-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 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
Covalent compoundsCovalent 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
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 covalentIf it is a non-metal use covalent
Ionic FormulasIonic Formulas Charges must add up to zeroCharges 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 listor memorized from the list use parenthesis to indicate multiple use parenthesis to indicate multiple
polyatomicspolyatomics
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 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
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 waterdissolved in water All acids begin with HAll 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 namesBackwards 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 crystalsform 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 trappedtrapped
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
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