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Chapter 3Chapter 3Structure of the AtomStructure of the Atom
Chapter 3 NotesChapter 3 Notes
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BrainteaserBrainteaser
What makes one What makes one element different from element different from another?another?
In the beginning….there were only In the beginning….there were only the elements which were divided the elements which were divided based on their properties.based on their properties.
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Chemical SymbolsChemical Symbols
A letter or letter pair that A letter or letter pair that represents the name of an represents the name of an element, similar to an element, similar to an abbreviation.abbreviation.
C = Carbon C = Carbon Ag = Argentum (latin) = SilverAg = Argentum (latin) = Silver
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Types of Sub-Atomic ParticlesTypes of Sub-Atomic Particles
TypeType SymbolSymbol (amu) (amu) LocationLocationProton Proton (+) (+) 1 1 nucleusnucleusNeutron Neutron (n) (n) 1 1 nucleusnucleusElectronElectron (-) (-) 0 0 around thearound the
nucleusnucleus
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Types of Sub-Atomic ParticlesTypes of Sub-Atomic Particles
Type Symbol Type Symbol R. Mass R. Mass LocationLocation Proton Proton (+) (+) 1836 1836 nucleusnucleus Neutron (n) Neutron (n) 1839 1839 nucleusnucleus Electron (-) Electron (-) 1 1 around thearound the
NucleusNucleus
Differences in atoms arise from Differences in atoms arise from differences in the amounts of differences in the amounts of each particle in the atom. each particle in the atom.
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About The AtomAbout The Atom
Mass NumberMass Number – the number of – the number of protons + number of neutrons, very protons + number of neutrons, very similar to the atomic mass.similar to the atomic mass.
Atomic NumberAtomic Number – The number of – The number of protons in the nucleus of an atom.protons in the nucleus of an atom.
Number of NeutronsNumber of Neutrons = mass number = mass number – atomic number– atomic number
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88
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Practice ProblemsPractice ProblemsHow Many How Many
Protons/Neutrons/Electrons are Protons/Neutrons/Electrons are present in:present in:
LithiumLithiumSodiumSodiumBerylliumBerylliumGoldGold
What is the atomic number for:What is the atomic number for:CarbonCarbonHeliumHeliumIronIronCopperCopper
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Changing the AtomChanging the Atom
1.1. Change the number of Change the number of ProtonsProtons New New AtomAtom, new properties, new properties
2.2. Change the number of Change the number of NeutronsNeutrons New New IsotopeIsotope (could be radioactive) (could be radioactive)
3.3. Change the number of Change the number of ElectronsElectrons New New IonIon (holds a charge) (holds a charge)
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Changing the Number of Changing the Number of ProtonsProtons
New Element, New PropertiesNew Element, New Properties
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The Periodic TableThe Periodic Table
Brainteaser:Brainteaser: How would you How would you orderly arrange the pencils and orderly arrange the pencils and pens of each member of our pens of each member of our class? class?
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1800 – Dimitri Mendeleev (Russian)1800 – Dimitri Mendeleev (Russian)Organized the periodic table of the Organized the periodic table of the
elementselementsPeriodicPeriodic – repeated in a pattern – repeated in a patternChemical properties of the lighter Chemical properties of the lighter
elements repeated in the heavier elementselements repeated in the heavier elementsLeft empty spaces based on the properties Left empty spaces based on the properties
of elements not yet discovered (Ge)of elements not yet discovered (Ge)Organized left to right based on Organized left to right based on massmass
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Dimitri’s Periodic
Table
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Modern ModificationsModern Modifications
19131913 - Mosley reorganized left - Mosley reorganized left to right based on atomic to right based on atomic number number
always increasesalways increases
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GroupsGroupsGroupsGroups – Vertical columns – Vertical columnsSimilar propertiesSimilar propertiesSame number of electrons in Same number of electrons in
their outer shelltheir outer shell
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PeriodsPeriodsPeriodsPeriods – Horizontal rows – Horizontal rowsL to R increase in atomic numberL to R increase in atomic numberUp to down increase in electron Up to down increase in electron
shell energy levelshell energy level
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The Periodic TableThe Periodic Table
MetalsMetals – good conductors, solids – good conductors, solids at room temperature, shiny.at room temperature, shiny.
NonmetalsNonmetals – mostly gases, – mostly gases, brittle, bad conductorsbrittle, bad conductors
MetalloidsMetalloids – have properties of – have properties of both metals and non-metalsboth metals and non-metals
Hg – BrHg – Br only liquids on the only liquids on the periodic tableperiodic table
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The Periodic TableThe Periodic Table
2020
The FamiliesThe FamiliesAlkali Metals – Group 1Alkali Metals – Group 1Alkaline Earth Metals – Group 2Alkaline Earth Metals – Group 2Chalcogens – Group 16Chalcogens – Group 16Halogens – Group 17Halogens – Group 17Nobel Gases – Group 18Nobel Gases – Group 18Transition Metals – Groups 3-12Transition Metals – Groups 3-12Lanthanides – Top Row BottomLanthanides – Top Row BottomActinides – Bottom Row BottomActinides – Bottom Row Bottom
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Periodic PropertiesPeriodic Properties
More reactive at the edges of the tableMore reactive at the edges of the tableNoble gasses do not reactNoble gasses do not react
Periodic Trends: Periodic Trends: increases if…increases if…ElectronegativityElectronegativity – electron greedy (Up – electron greedy (Up
and Right)and Right)SizeSize – (Down and Left) – (Down and Left) Ionization EnergyIonization Energy – electron give away – electron give away
(down and left)(down and left)
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The Periodic TableThe Periodic Table
Diatomic MoleculesDiatomic Molecules – molecules – molecules made of two atomsmade of two atomsNaturally occurring on the Naturally occurring on the
periodic tableperiodic tableBr-I-N-Cl-H-O-FBr-I-N-Cl-H-O-F
AllotropesAllotropes – Different forms of the – Different forms of the same elementsame element
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AllotropesAllotropes
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Changing the Number of Changing the Number of NeutronsNeutrons
Isotopes…RadioactivityIsotopes…Radioactivity
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IsotopesIsotopes
IsotopesIsotopes – atoms of the same – atoms of the same element that have a different number element that have a different number of neutrons.of neutrons.
QuestionQuestion:: Iodine is found in one of Iodine is found in one of two isotopes, I-131 and I-130. How two isotopes, I-131 and I-130. How many Neutrons are present in each?many Neutrons are present in each?
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Average Atomic MassAverage Atomic Mass
Average atomic mass – Average atomic mass – the the average mass of the mixture of its average mass of the mixture of its isotopes (different from the actual isotopes (different from the actual atomic mass)atomic mass)
QuestionQuestion:: If we have 5 atoms, 4 with If we have 5 atoms, 4 with the atomic mass of 11 and one with the atomic mass of 11 and one with the atomic mass of 10, what is the the atomic mass of 10, what is the average atomic mass?average atomic mass?
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Practice ProblemsPractice Problems
Question:Question: a chlorine atom has 17 a chlorine atom has 17 protons and 18 neutrons. What is the protons and 18 neutrons. What is the mass number? What is the atomic mass number? What is the atomic number?number?
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RadioactivityRadioactivity
Some Isotopes are radioactive, they are Some Isotopes are radioactive, they are too heavy (filled with neutrons) to be too heavy (filled with neutrons) to be stablestable
They give off radiation to “transmutate” They give off radiation to “transmutate” and become a lighter, more stable elementand become a lighter, more stable element
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Types of RadiationTypes of Radiation AlphaAlpha – two neutrons and two protons given – two neutrons and two protons given
off (one electron shy of being helium) off (one electron shy of being helium)
BetaBeta – losing a positive charge, a proton – losing a positive charge, a proton converts to a neutron.converts to a neutron.
GammaGamma – no mass, but high energy given – no mass, but high energy given off by the nucleusoff by the nucleus
Types of RadiationTypes of Radiation
RnHeRa 21886
42
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ePaTh 01
23491
23490
0023490
42
23892 2 ThHeU
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Calculating Half LifeCalculating Half Life
The amount of radioactive isotope remaining can The amount of radioactive isotope remaining can be calculated:be calculated:
NNtt = N = Noo x (0.5) x (0.5) (number of half-lives)(number of half-lives)
NNtt = amount of radioisotope remaining = amount of radioisotope remaining
NNoo = original amount of radioisotope = original amount of radioisotope
number of half-lives = time ÷ half-life number of half-lives = time ÷ half-life
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Uses of RadiationUses of Radiation Half Life – Radio Carbon Dating (Half Life – Radio Carbon Dating (ArchiologyArchiology))
Radioactive Tracers (Medicine)Radioactive Tracers (Medicine)
Effects of Radiation on the BodyEffects of Radiation on the Body
Fission vs. FusionFission vs. Fusion
Atomic WeaponsAtomic Weapons (Fission and Fusion) (Fission and Fusion)
Using Radiation for Energy (Nuclear Power)Using Radiation for Energy (Nuclear Power) (Fission) (Fission)
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Changing the Number of Changing the Number of ElectronsElectrons
IONSIONS
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Drawing Planetary ModelsDrawing Planetary Models
1.1. Find Atomic Number = Number of Find Atomic Number = Number of ElectronsElectrons
2.2. Circle for nucleus including Circle for nucleus including number of protons and neutrons number of protons and neutrons (+ =, n =)(+ =, n =)
3.3. Draw orbits with correct number of Draw orbits with correct number of electrons in each, filling in to outelectrons in each, filling in to out
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Drawing Planetary ModelsDrawing Planetary Models
Energy LevelEnergy Level Number of Number of ElectronsElectrons
11 22
22 88
33 1818
44 3232
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Practice ProblemsPractice Problems
Draw Planetary Models for the Draw Planetary Models for the Following:Following:
LithiumLithiumCarbonCarbonIronIron
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Lewis Dot StructuresLewis Dot Structures
A diagram of an atoms showing A diagram of an atoms showing the valence electronsthe valence electrons
Valence electronsValence electrons – outer – outer electronselectronsWhere all exciting chemistry Where all exciting chemistry
happenshappens
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How to Draw Lewis Dot StructuresHow to Draw Lewis Dot Structures
1.1. Period = Energy levelPeriod = Energy level
2.2. Skipping the transition metals Skipping the transition metals and counting group 1 as 1, count and counting group 1 as 1, count right to the position of your right to the position of your element.element.
3.3. The number = the electrons in The number = the electrons in the outer shellthe outer shell
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How to Draw Lewis Dot StructuresHow to Draw Lewis Dot Structures
4.4. Draw the element symbolDraw the element symbol5.5. Draw one dot on each of the Draw one dot on each of the
4 sides, then double up when 4 sides, then double up when necessary (max 8 dots)necessary (max 8 dots)
Octet RuleOctet Rule – Atoms considered – Atoms considered to be stable have 8 electrons in to be stable have 8 electrons in their outermost shelltheir outermost shell
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Practice ProblemsPractice ProblemsGive the periodic group number and Give the periodic group number and
number of valence electrons for number of valence electrons for each of the following atoms:each of the following atoms:
CC ClCl NeNe SiSi SeSe AlAl
Write Lewis Dot Structures for:Write Lewis Dot Structures for: KK MgMg SS ArAr
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IonsIons
All atoms are naturally neutral All atoms are naturally neutral (0 charge)(0 charge)
Electrons can be gained and Electrons can be gained and lost to create a net + or – lost to create a net + or – chargecharge
Na Na → Na→ Na++ + e + e- - (Ionic Equation)(Ionic Equation)
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IonsIons
CationsCations – positive ion – formed when – positive ion – formed when one or more electrons are one or more electrons are lostlost from from an atoman atomNa Na → Na→ Na++ + e + e--
AnionAnion – negative ion – formed when – negative ion – formed when one or more electrons are one or more electrons are gainedgainedCl Cl + e+ e- - → → CCll--
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IonsIonsIons are formed in repeated Ions are formed in repeated
predictable patterns found on the predictable patterns found on the periodic tableperiodic table
Gaining or losing electrons to reveal Gaining or losing electrons to reveal an octet – atom’s goalan octet – atom’s goal
Alkalli metals – all (+1)Alkalli metals – all (+1)Halogens – all (-1)Halogens – all (-1)Transition metals – form (+) ionsTransition metals – form (+) ions
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Periodic IonsPeriodic Ions
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Ionic CompoundsIonic Compounds
Ions separate in solutionIons separate in solutionHigh melting pointsHigh melting pointsMostly between metals and Mostly between metals and
nonmetalsnonmetalsCharged ions in solution carry current Charged ions in solution carry current
through solution or when melted – through solution or when melted – conduct electricityconduct electricitySaltwater vs. WaterSaltwater vs. Water
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Ionic CompoundsIonic CompoundsMust have one cation and one Must have one cation and one
anion (metal and non-metal)anion (metal and non-metal)Total charge must equal Total charge must equal zerozeroMultiply either the positive or Multiply either the positive or
negative ion by a factor until sum negative ion by a factor until sum is zerois zero
Chemical BondChemical Bond – a force that – a force that holds together the atoms in a holds together the atoms in a substancesubstance
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Writing Molecular FormulasWriting Molecular Formulas
Listing of the types of atoms Listing of the types of atoms (chemical symbols) and numbers (chemical symbols) and numbers (subscripts) of each in a molecule(subscripts) of each in a moleculeNN22OO55
SOSO33
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Why atoms bondWhy atoms bond
Atoms wish to be chemically Atoms wish to be chemically stablestable
Octet RuleOctet Rule – an element is stable – an element is stable when it has 8 outer electronswhen it has 8 outer electrons
An atom will seek to have 8 outer An atom will seek to have 8 outer electrons by bonding or by electrons by bonding or by gaining or loosing electronsgaining or loosing electrons
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Ionic CompoundsIonic Compounds
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Practice ProblemsPractice Problems
What is the molecular formula for:What is the molecular formula for:Sodium and ChlorineSodium and ChlorineMagnesium and ChlorineMagnesium and Chlorine
Show how each compound is Show how each compound is formedformed
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AnswersAnswers
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The EndThe End
Good Luck with the Good Luck with the Chapter 3 testChapter 3 test
Major Topics:Major Topics:
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Atomic HistoryAtomic History
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Mental Models of the AtomMental Models of the Atom
It is yet impossible to obtain a true It is yet impossible to obtain a true picture of the structure of an atompicture of the structure of an atom
Scientists are left to best guesses Scientists are left to best guesses based on observations during a based on observations during a series of experimentsseries of experiments
With each breakthrough, the With each breakthrough, the model had to changemodel had to change
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Greeks (400 B.C.) - DemocritusGreeks (400 B.C.) - Democritus
The atom is made of (+) and (-) bitsThe atom is made of (+) and (-) bits
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1808 - Dalton – Atomic Theory1808 - Dalton – Atomic Theory
ObservedObserved::Natural materials = pure Natural materials = pure
substancessubstancesPure substances are either Pure substances are either
elements or compoundselements or compoundsCompounds always have same Compounds always have same
proportions of elementsproportions of elements
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1808 - Dalton – Atomic Theory1808 - Dalton – Atomic TheoryElements are made of tiny “atoms”Elements are made of tiny “atoms”Atoms in an element are identicalAtoms in an element are identicalAtoms from one element are different Atoms from one element are different
from those of anotherfrom those of anotherAtoms can combine to form compoundsAtoms can combine to form compoundsAtoms are indivisible by chemical meansAtoms are indivisible by chemical means
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DaltonDalton
Law of constant composition – a
compound always has the same composition
MOV
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1890 – J.J. Thomson – 1890 – J.J. Thomson – Plum Pudding ModelPlum Pudding Model
Showed elements have negative pieces by Showed elements have negative pieces by repelling them with magnetic field – repelling them with magnetic field – electronelectron
Overall charge is zero – must have positive Overall charge is zero – must have positive piecespieces
Positive ball with negative pieces sprinkled Positive ball with negative pieces sprinkled inin
MOVMOV
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1913 – Ernest Rutherford1913 – Ernest Rutherford
Gold Foil ExperimentGold Foil Experiment wrapped piece of wrapped piece of gold foil with gold foil with photographic paper photographic paper and bombarded with and bombarded with alpha particlesalpha particles
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Gold Foil ExperimentGold Foil Experiment
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1913 – Ernest Rutherford1913 – Ernest RutherfordMost passed through – thus atoms Most passed through – thus atoms
are mostly empty spaceare mostly empty spaceAlpha particles slightly thrown off Alpha particles slightly thrown off
course – (+) small center - protoncourse – (+) small center - protonEmpty space contains the Empty space contains the
electronselectronsmovmov
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1913 – Ernest Rutherford1913 – Ernest Rutherford
Cloud ModelCloud Model (nuclear atom) – (nuclear atom) – Cloud of electrons surrounding a Cloud of electrons surrounding a central positive nucleuscentral positive nucleus
Nucleus is 1/100,000 of the total Nucleus is 1/100,000 of the total size (a paperclip inside a stadium)size (a paperclip inside a stadium)
MOVMOV
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1926 - Niels Bohr (planetary 1926 - Niels Bohr (planetary model)model)
Quickly re-developed to place Quickly re-developed to place electrons in well-defined paths electrons in well-defined paths around a central nucleusaround a central nucleus
MOVMOV
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Present Day:Present Day:
It is impossible to know the It is impossible to know the location of an electron at any one location of an electron at any one timetime
Scientists can generate pictures Scientists can generate pictures based on the probability of the based on the probability of the locations of the electronslocations of the electrons
MOVMOV