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Chapter 4 Chapter 4 Atomic Atomic Structure Structure p. 101 p. 101

Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

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Page 1: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Chapter 4Chapter 4Atomic Atomic

StructureStructurep. 101p. 101

Page 2: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Section 4.1 Defining the AtomSection 4.1 Defining the Atom Greek philosopher Greek philosopher DemocritusDemocritus

suggested atoms (Greek suggested atoms (Greek “atomos”)“atomos”) Believed Believed indivisibleindivisible & &

indestructibleindestructible His ideas His ideas

Based on philosophyBased on philosophy didn’t explain chem behaviordidn’t explain chem behavior Lacked experimental support Lacked experimental support

Page 3: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Dalton’s Atomic TheoryDalton’s Atomic Theory (experiment based!) (experiment based!)

3) Atoms of diff elements combine in simple whole # ratios (chem cmpds)

4) In chem rxns, atoms combine, separate, or rearrange – never change into atoms of another element

1) All elements composed of indivisible particles (atoms)

2) Atoms of same element identical. Atoms of 1 different from other elements

John Dalton(1766 – 1844)

Page 4: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Sizing up the AtomSizing up the Atom Elements subdivided into smaller particles – atoms,… still have properties of that element

Line up 1.0 x 108 copper atoms = 1 cm longindividual atoms observed w/ scanning tunneling (electron) microscopes

The atom 1:15

Page 5: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Section 4.2Section 4.2Structure of the Nuclear AtomStructure of the Nuclear Atom

One change to Dalton’s atomic One change to Dalton’s atomic theory - theory - atoms ARE divisibleatoms ARE divisible

Into subatomic particles:Into subatomic particles:

Electrons, protons, and Electrons, protons, and neutronsneutrons

Page 6: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Discovery of ElectronDiscovery of Electron1897 - J.J. Thomson used cathode ray tube to deduce presence of negatively charged

particle…….electronelectron

JJ Thomson’s Cathode Ray 2:49

Page 7: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Mass of ElectronMass of Electron

1916 – Robert Millikan determines e- mass: 1/1840 mass of H atom; one unit of - charge

The oil drop apparatus

Mass of the electron is 9.11 x 10-28 g

Page 8: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Conclusions from the Study Conclusions from the Study of the Electron:of the Electron:

a) All elements must contain identically charged e-s.

b) Atoms r neutral, must be + particles to balance – e-s

c) e-s have little mass - atoms must contain other more massive particles

Page 9: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Conclusions from Electron Conclusions from Electron Study:Study:

1932 – James Chadwick confirmed “neutron” existence

particle w/ no chargen0 mass = p+ mass

Page 10: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Subatomic ParticlesSubatomic Particles

ParticleParticle ChargeCharge Mass (g)Mass (g) LocationLocation

ElectronElectron

(e(e--)) 1-1- 9.11 x 109.11 x 10-28-28 Electron Electron cloudcloud

ProtonProton (p(p++)) 1+1+ 1.67 x 101.67 x 10-24-24 NucleusNucleus

NeutronNeutron

(n(noo)) 00 1.67 x 101.67 x 10-24-24 NucleusNucleus

Page 11: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Thomson’s Atomic ModelThomson’s Atomic Model

Believed e-s like plums in + charged “pudding,” ----- “plum pudding” model.

J. J. Thomson

Page 12: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Ernest Rutherford’sErnest Rutherford’sGold Foil Experiment - 1911Gold Foil Experiment - 1911

massive alpha particles (He atom w/o e-’s) fired at Au foilThought most would pass thru w/ slight deflectionMOST passed straight thru!

Rutherford’s Gold Foil Experiment 4:06

Page 13: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Rutherford’s problem:Rutherford’s problem:In the following pictures, there is a target hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloud and recorded where the beams came out. Can you figure out the shape of the target?

Target #1

Target #2

Page 14: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

The Answers:The Answers:

Target #1 Target #2

Page 15: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Rutherford’s FindingsRutherford’s Findings Most particles passed thru Few deflected VERY FEW greatly deflected

The Atom The Atom SongSong

Atoms song - Mark Rosengarten

“As incredible as howitzer shells bouncing off of tissue paper!”

Page 16: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

The Rutherford Atomic ModelThe Rutherford Atomic Model New theory:New theory:

atom mostly empty spaceatom mostly empty space NucleusNucleus

pp++ & n & n00 m makeake nucleus! nucleus!all + chargeall + chargealmost all massalmost all mass

e-s around nucleus…occupy most e-s around nucleus…occupy most volumevolume

called “called “nuclear modelnuclear model””

Rutherford’s Atom 3:08

Quarks 2:56

Page 17: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Section 4.3Section 4.3Distinguishing Among Atoms Distinguishing Among Atoms

p. 110p. 110

How are elements different How are elements different from one another?from one another?

different # different # p+’s!p+’s! ID’s elements (like fingerprint/DNA)ID’s elements (like fingerprint/DNA)

Page 18: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Atomic NumberAtomic NumberAtomic number (Z) of element = # of p+’s in nucleus of each atom of that of that element.element.

ElementElement # of protons# of protons Atomic # (Z)Atomic # (Z)

CarbonCarbon 66

PhosphorusPhosphorus 1515

GoldGold 7979

615

79

Page 19: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Mass NumberMass Number

Mass number is # of p+’s and n0’s in nucleus of isotope:

nn0 0 = mass # - atomic = mass # - atomic ## pp++ nn00 ee-- Mass #Mass #

Oxygen Oxygen - - 1010

- - 3333 4242

- - 3131 1515

8 8 1818

Arsenic 75 33 75

Phosphorus 15 3116

Page 20: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Complete SymbolsComplete Symbols

X Massnumber

Atomicnumber

Subscript →

Superscript →

Page 21: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

SymbolsSymbols Identify each of these: Identify each of these:

a)a) number of protonsnumber of protons

b)b) number of neutronsnumber of neutrons

c)c) number of electronsnumber of electrons

d)d) Atomic numberAtomic number

e)e) Mass NumberMass Number

Br80 35

Page 22: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Practice…..Practice….. If an element has an atomic If an element has an atomic

number of 34 and a mass number of 34 and a mass number of 78, what is the: number of 78, what is the:

a)a) number of protonsnumber of protons

b)b) number of neutronsnumber of neutrons

c)c) number of electronsnumber of electrons

d)d) complete symbolcomplete symbol

Page 23: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

More practice…….More practice……. If an element has 91 If an element has 91

protons and 140 neutrons protons and 140 neutrons what is the what is the

a)a) Atomic numberAtomic number

b)b) Mass numberMass number

c)c) number of electronsnumber of electrons

d)d) complete symbolcomplete symbol

Page 24: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

IsotopesIsotopes

Dalton was wrong!Dalton was wrong!Atoms of same elements NOT Atoms of same elements NOT

identical…identical…cancan have different # have different # nn00’s’s..

different mass #different mass #Isotopes Isotopes

(flavors)(flavors)

Page 25: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

IsotopesIsotopes Frederick SoddyFrederick Soddy

proposed idea of isotopes proposed idea of isotopes in 1912in 1912 1921 Nobel Prize in Chemistry 1921 Nobel Prize in Chemistry crater w/ his name on far side of crater w/ his name on far side of

MoonMoon

Isotopes - atoms of same element w/ diff masses b/c varying #s of n0

Elements occur in nature as Elements occur in nature as mixturesmixtures of of isotopes.isotopes.

Page 26: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Naming IsotopesNaming Isotopes

put mass # put mass # afterafter element element name:name:carbon-12 carbon-12 fluorine-19fluorine-19uranium-235uranium-235

Page 27: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

IsotopeIsotope ProtonsProtons ElectronsElectrons NeutronsNeutrons NucleusNucleus

Hydrogen–1Hydrogen–1

(protium)(protium) 11 11 00

Hydrogen-2Hydrogen-2

(deuterium)(deuterium) 11 11 11

Hydrogen-3Hydrogen-3

(tritium)(tritium)

11 11 22

Page 28: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Atomic MassAtomic Mass How heavy is an oxygen atom?How heavy is an oxygen atom?

Depends, b/c different Depends, b/c different kindskinds of oxygen of oxygen atoms exist.atoms exist.

average average atomic massatomic mass Based on abundance (%) of each variety Based on abundance (%) of each variety

of that element in nature.of that element in nature. not in grams - #’s tooooo smallnot in grams - #’s tooooo small

Page 29: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Measuring Atomic MassMeasuring Atomic Mass

Atomic Mass UnitAtomic Mass Unit (amu)(amu) 1/12 mass of C-12 atom1/12 mass of C-12 atom

C-12 b/c C-12 b/c isotope purityisotope purity Each isotope has own atomic mass Each isotope has own atomic mass determine average from % abundancedetermine average from % abundance

Page 30: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

To calculate weighted To calculate weighted average mass:average mass:

Atomic massAtomic mass xx isotope isotope abundance (change % to abundance (change % to decimal)decimal)

Add all resultsAdd all results Isotope mass usually in Isotope mass usually in amuamu’s’s

Page 31: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

Atomic MassesAtomic Masses

IsotopeIsotope SymbolSymbol Composition Composition of the nucleusof the nucleus

% in nature% in nature

Carbon-Carbon-1212

1212CC 6 protons6 protons

6 neutrons6 neutrons

98.89%98.89%

Carbon-Carbon-1313

1313CC 6 protons6 protons

7 neutrons7 neutrons

1.11%1.11%

Carbon-Carbon-1414

1414CC 6 protons6 protons

8 neutrons8 neutrons

<0.01%<0.01%

Atomic mass - avg of all naturally occurring isotopes of that element

12.01What is the average atomic mass of Carbon?What is the average atomic mass of Carbon?

Atomic Atomic mass mass (amu)(amu)

12

13.00

14.00

Page 32: Chapter 4 Atomic Structure p. 101. Section 4.1 Defining the Atom Greek philosopher Democritus Greek philosopher Democritus suggested atoms (Greek “atomos”)

- Page 117

Question

Solution

Answer

Knowns and Unknown


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