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Chemistry Day 9 Monday, September 23rd – Tuesday,
September 24th, 2019
Do-Now Title: “Brainstorm: Unit 1” 1. Write down today’s FLT 2. Draw what an atom looks like according to
Democritus and Dalton 3. Draw what an atom looks like according to J.J.
Thomson 4. Draw what an atom looks like according to Ernest
Rutherford 5. Use one of the pro-talk sentence frames to tell me
something we have learned about atoms or subatomic particles.
6. Underneath your do-now, write “Brainstorm list” and number 1-20
Finished? Take out your planner and table of contents.
FLT • I will be able to calculate the mass
number and number of neutrons in an atom by completing Atoms CN
Standard HS-PS1-8:Developmodelstoillustratethechangesinthecompositionofthenucleusoftheatomandtheenergyreleasedduringtheprocessesoffission,fusion,andradioactivedecay
Distinguishing Among Atoms
Guiding Questions • Whatmakeselementsandisotopesdifferent?• Howcanwecalculatethenumberofneutronsinanatom?
• HowcanIcalculatetheatomicmassofanelement?
• CanIexplainwhychemistsusetheperiodictable?
Recall • An atom’s atomic number (Z) = the number
of protons in the nucleus. Defines element.
Recall • Elementsaredifferentbecausetheycontaindifferentnumbersofprotonsàifyouchangethenumberofprotons,youchangetheelement
Recall • Atoms are
electrically neutral • Protonshavea+1charge
• Whatbalancesthem?• Electronshavea-1charge
• Therefore,protons=electronsinanatom
Groups have similar properties GroupsaretheVERTICALCOLUMNS
Mass Number • Recall:
– Protonshavearelativemassof1
– Neutronshavearelativemassof1
– Electronshavearelativelyinsignificantmass
Mass Number • Massnumber=p++n0• Copy and complete the table below
Nuclide p+ n0 e- Mass #
Oxygen -
10
- 33 42
- 31 15
8 8 1818
Shorthand Notation MassNumber
AtomicNumber
Symbol
Shorthand Notation ■ Find each of these:
a) number of protons
b) number of neutrons
c) number of electronsd) Atomic number
e) Mass Number C 14
6
Shorthand Notation ■ If an element has an atomic number of
34 and a mass number of 78, what is the: a) number of protonsb) number of neutrons
c) number of electronsd) shorthand notation
Isotopes • What was Dalton mistaken about? • Dalton was also wrong about all elements of
the same type being identical
Isotopes • Atoms of the same element can have
different numbers of neutrons.• Thus, different mass numbers.• These are called isotopes.
Isotopes • FrederickSoddy(1877-1956)proposedtheideaofisotopesin1912
• Isotopes=atomsofthesameelementhavingdifferentmasses,duetovaryingnumbersofneutrons.
• SoddywontheNobelPrizeinChemistryin1921forhisworkwithisotopesandradioactivematerials.
Isotopes
• We can also put the mass number after the name of the element: – carbon-12 – carbon-14 – uranium-235
Isotopes Isotope Protons Electrons Neutrons Nucleus
Hydrogen–1
(protium)
1
1
0
Hydrogen-2
(deuterium)
1
1
1
Hydrogen-3
(tritium)
1
1
2
Isotopes
• Elements occur in nature as mixtures of isotopes.
Atomic Mass § Howheavyisanatomofoxygen?§ Itdepends,becausetherearedifferentkindsofoxygenatoms.
§ Wearemoreconcernedwiththeaverageatomicmass.
§ Averageatomicmass=weightedaverageoftheisotopesofagivenelementbasedonthepercentabundanceinnature
Atomic Mass • Each isotope has its own atomic
mass, thus we determine the average from percent abundance.
Calculating Atomic Mass • Multiply the atomic mass of
each isotope by its abundance (expressed as a decimal), then add the results.
• If not told otherwise, the mass of the isotope is expressed in atomic mass units (amu)
Example Anelementhasthefollowingnaturalabundancesandisotopicmasses:90.92%abundancewith19.99amu,0.26%abundancewith20.99amu,and8.82%abundancewith21.99amu.Calculatetheaverageatomicmassofthiselement.Solution:Averageatomicmass=(0.9092×19.99amu)+(0.0026×20.99amu)+(0.0882×21.99amu)Averageatomicmass=20.17amuMakesuretoshowworkandunitsJ
Pair-Share-Respond 1. What is Z? 2. Can atoms of the same element have
different numbers of protons? 3. Discuss all information you can
derive from the shorthand notation pictured
4. Explain how isotopes differ from one another.
5. What is meant by the term “average atomic mass”?
Chemistry Day 10 Wednesday, September 25th – Thursday,
September 26th, 2019
Do-Now Title: “Nuclear Notation Review” 1. Answer the do-now questions on your
worksheet 2. If you finish early, you may start on the back.
Otherwise, it is part of our classwork. You may not work on it once we start our announcements.
Finished? Take out your planner and table of
contents.
FLT • I will be able to describe the three main
types of nuclear radiation by completing Ch. 19 CN A
Standard HS-PS1-8:Developmodelstoillustratethechangesinthecompositionofthenucleusoftheatomandtheenergyreleasedduringtheprocessesoffission,fusion,andradioactivedecay
Ch. 19 Part A: Radiation
Review–AtomicModels
Nucleons and Nuclear Forces
SubatomicParticles• In1932,JamesChadwickdiscoveredtheneutron
• Thiswasimportantinimprovingtheproton-electronatomicmodel
• Newmodel:Theproton-neutronnucleus
Proton-NeutronModel
SubatomicParticles• Wenowhavethreesubatomicparticles:– Protonsp+– Electronse-– Neutronsn0
• Nucleons=subatomicparticleslocatedinthenucleusofatoms(p+andn0)– Nucleonsarecomposedofsmallerparticlescalledquarks
Forces• Therearetwomainforcesatplayinournucleus:
– Electromagneticforce(proton-protonrepulsion)– Strongforce(nucleonssticktogether)
Forces• Notallnucleiarestable
– Positively-chargedprotonscanrepeleachother• StrongNuclearForce=bindsp+andn0togetherinthenucleus
Unstable Nuclei – Strongforce=holdsnucleitogetherovershortdistances
– Largernucleicanbemoreunstable
Nuclear Stability
NuclearStability• StrongNuclearForce
– Thisforcecanonlyactoververyshortdistances– Itisthestrongestattractiveforce(137timesmorethanelectromagnetic)
– Overextremelyshortdistances,thestrongnuclearforceoverridestherepulsionoftheelectromagneticforce
• Lookingattheratioofprotonstoneutronscanhelpusdeterminethestabilityofthenucleus
Band of Stability
• The region on a graph which indicates all stable nuclei when the number of neutrons are compared to the number of protons for all stable nuclei
NuclearStability• Largernuclidestendtobemoreunstable
– Allnuclideswithmorethan83protons(bismuth)areunstable
• Mostnuclideswanta1:1ofneutrons:protons– Heaviernuclidesneedmoreneutrons
Pair-Share-Respond 1. Whatarenucleons?2. Explainthetypesofforcesoccurringwithinanucleus
3. Describetwodifferenttypesofnucleithatareunstable
Radioactivity
Radioactivity
• Howdoesanunstablenucleusreleaseenergy?
Context • MarieCurie(1867-1934)helpeddiscovernewelements(PoloniumandRadium),aswellasradioactiveelements
• Curiestudiedmaterialsthatgaveoffrays,whichshecalledradioactivity
Radiation • Radiation=Rays&particlesemittedbyaradioactivesource
Radiation Radioisotopes=unstableisotopeswhosenucleiundergochangestobecomemorestable
Radioactivity
– Anunstablenucleus“decays”intoanewnucleusbychangingitsnumberofprotonsspontaneously
– Ifthenumberofprotonschanges,isitthesameelementanymore?
Radioactivity – Radioactivedecay=unstablenucleusreleasesenergy/emitsradiation
Types of Radiation
Types of Radiation
What are the three main types of nuclear radiation?
Main Types of Radiation
1. Alpha (α) Radiation 2. Beta (β) Radiation 3. Gamma (Υ) Radiation
Alpha Radiation Alpha radiation = Emits alpha particles (helium) • Mass number decreases by 4, atomic number
decreases by 2
Alpha Radiation Ex/
Beta Radiation
• Beta Radiation = Emits a beta particle (electron) – Mass number stays the same. Atomic number increases by
1.
Beta Radiation Ex/
Gamma Radiation
• Gamma radiation = Emits a high-E photon(gamma ray).
• Tends to accompany other nuclear decay processes
Types of Radiation
• Alphaparticlesaretheleastpenetrating.Gammaraysarethemostpenetrating.
Figure4.2:Thepenetratingpowerofradiation.
© 2003 John Wiley and Sons Publishers
Arethereothertypesofdecay?
α-particleproduction
Spontaneousfission
β-particleproduction
Positronproduction
γ-rayproduction
Positron Production
• Positron = positively charged anti-electron
Pair-Share-Respond 1. Whatareradioisotopes?2. Whatareourthreemaintypesof
radiation?3. Whichtypeisthemostdangerous?4. Whatisemittedinbetadecay?5. Whatisemittedinalphadecay?
Chemistry Day 11 Friday, September 27th, 2019
Do-Now Title: “BrainPOP: Radioactivity” 1. Write down today’s FLT 2. What is your current grade in this class? 3. Is your grade where you want it to be? If not,
what will you do to change it? 4. What is the most difficult part of this class so
far? 5. Define the term “radioisotope”. Even better if
you can do it without referring to the notes. 6. Underneath your do-now, write “brainpop
practice” and number 1-10 Finished? Take out your planner and table of
contents.
Add to do-now paper: 1. Use a pro-talk sentence frame to tell me
something about radioactivity. 2. You have isolated one kilogram of pure Mobium,
a new radioactive substance. When Mobium decays, it becomes ordinary iron. You have a sample of 25 grams.
a. You wrap the sample in paper, and observe that radiation is no longer detectable. What kind of radiation is it (possibly) emitting?
b. After 6 hours, you notice that only 12.5 grams remain. Explain what happened.
3. List three examples of radioactive elements. 4. What are some risks of studying radioactive
elements?
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