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Lecture 2

BIOL 1201 Lecture Notes - Lecture 2: Mass Number, Atomic Number, MagnesiumPremium


Department
Biological Sciences
Course Code
BIOL 1201
Professor
Moroney, James
Lecture
2

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BIOL1201Lecture2BasicChemistry
BasicsofBiologicalElements
Atomicnumber:numberofprotons
● Massnumber:sumofprotonsandneutronsinanucleus,protons&neutronsweigh~1.7
X1024grams,electron1/2000
th
ofthat
● AtomicWeight:massoftheatom,approximatelythemassnumber
● Isotopes:sameatomicnumber,differentatomicweight.
o Unstableisotopesloseenergy:radioactive.
● NATURALCARBONISOTOPES(At.No.=6)
● ISOTOPE ABUNDANCE
● C12 98.8%
● C13 1.1%
● C14 trace(radioactive)C14isNATURALLYOCCURRING
o Allhavesamenumberofprotons,electrons,buthavedifferentnumberof
neutrons.Allverysimilar.Usedalotinbiology. 
o WeeatC14throughplants,oncewedietheC14ingestionstops.5000year
halflife,deadsamplescanbedatedusingthis.
● NATURALPOTASSIUMISOTOPES(At.No.=19)
● ISOTOPE ABUNDANCE
● K39 93.3%
● K40 0.0012%(radioactive)
● K41 6.88%
ElectronConfigurationandChemicalProperties
● Electronsfillsequential“shells”aroundatoms
● Shell1twoelectrons
● Shell2eightelectrons
● Shell3eightelectrons
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