CHAPTER 3 Atoms: The Building Blocks of Matter CHEMISTRY.
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Transcript of CHAPTER 3 Atoms: The Building Blocks of Matter CHEMISTRY.
CHAPTER 3CHAPTER 3Atoms: The Building Blocks of MatterAtoms: The Building Blocks of Matter
CHEMISTRYCHEMISTRY
Foundations of Atomic TheoryFoundations of Atomic Theory
HistoryHistory– GreekGreek
Democritus – “atom” – could not be divided anymoreDemocritus – “atom” – could not be divided anymore Aristotle and Plato - arguedAristotle and Plato - argued
– 1600-1700s1600-1700s Natural PhilosophersNatural Philosophers
– Experimentation – balances – quantitative measurementsExperimentation – balances – quantitative measurements
AtomAtom– Comes from GreekComes from Greek
““a” – nota” – not ““tomos” – cuttingtomos” – cutting indivisibleindivisible
Foundations of Atomic TheoryFoundations of Atomic Theory Chemical ReactionChemical Reaction
– Transformation of substances into one or more Transformation of substances into one or more new substancesnew substances
– Chemical changeChemical change Law of Conservation of MassLaw of Conservation of Mass
– Mass is neither created nor destroyed in Mass is neither created nor destroyed in ordinary chemical reactionsordinary chemical reactions
– http://www.youtube.com/watch?http://www.youtube.com/watch?v=dExpJAECSL8v=dExpJAECSL8
Law of Definite ProportionsLaw of Definite Proportions– A chemical compound contains the same A chemical compound contains the same
elements in exactly the same proportions by elements in exactly the same proportions by mass regardless of size of samplemass regardless of size of sample
– Ex – HEx – H22O, COO, CO22
Foundations of Atomic TheoryFoundations of Atomic Theory
Law of Multiple ProportionsLaw of Multiple Proportions– If two or more compounds are If two or more compounds are
composed of the same 2 elements, the composed of the same 2 elements, the masses can be expressed as ratios of masses can be expressed as ratios of small whole numberssmall whole numbers
Dalton’s Atomic TheoryDalton’s Atomic Theory
John DaltonJohn Dalton English School TeacherEnglish School Teacher 18031803
Dalton’s Atomic TheoryDalton’s Atomic Theory
5 Points in his theory5 Points in his theory– All matter is composed of extremely small All matter is composed of extremely small
particles called atomsparticles called atoms– Atoms of a given element are identical in size, Atoms of a given element are identical in size,
mass, and other propertiesmass, and other properties– Atoms cannot be subdivided, created, or Atoms cannot be subdivided, created, or
destroyeddestroyed– Atoms of different elements combine in simple Atoms of different elements combine in simple
whole number ratios to form compoundswhole number ratios to form compounds– In chemical reactions, atoms are combined, In chemical reactions, atoms are combined,
separated, or rearrangedseparated, or rearranged
Modern Atomic TheoryModern Atomic Theory
There have been some changes since There have been some changes since Dalton’s TheoryDalton’s Theory
Important concepts of modern theoryImportant concepts of modern theory– Atoms of one element can differ from Atoms of one element can differ from
each other - ISOTOPESeach other - ISOTOPES– An atom is made of smaller partsAn atom is made of smaller parts
Structure of the AtomStructure of the Atom
Atom – smallest particle of an element Atom – smallest particle of an element that can exist alone that can exist alone – Two regions of an atomTwo regions of an atom
NucleusNucleus– Center of atomCenter of atom– Protons and neutronsProtons and neutrons
Electron “cloud”Electron “cloud”– Area surrounding nucleus Area surrounding nucleus
containing electronscontaining electrons
Discovery of the electronDiscovery of the electron
Symbol Symbol e e--
Cathode ray tubes (CRT)Cathode ray tubes (CRT)– Vacuum tube containing an electron gun (a source of Vacuum tube containing an electron gun (a source of
electrons) and a fluorescent screen, with internal or external electrons) and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to means to accelerate and deflect the electron beam, used to form images in the form of light emitted from the fluorescent form images in the form of light emitted from the fluorescent screen. screen.
– Used in TV, computer monitorsUsed in TV, computer monitors
Discovery of the electronDiscovery of the electron
Charge and mass of the electronCharge and mass of the electron– JJ Thomson – 1897JJ Thomson – 1897
Discovered the electronDiscovered the electron 1907 Nobel Prize in Physics1907 Nobel Prize in Physics http://videos.howstuffworks.com/hsw/6298-atomic-shttp://videos.howstuffworks.com/hsw/6298-atomic-s
tructure-electrons-video.htmtructure-electrons-video.htm Did experiments with CRT – Did experiments with CRT –
– Found that the charge to mass Found that the charge to mass
ration was always the sameration was always the same
Discovery of the atomic nucleusDiscovery of the atomic nucleus
Ernest Rutherford – 1908Ernest Rutherford – 1908 Gold Foil ExperimentGold Foil Experiment
Composition of the nucleusComposition of the nucleus
ProtonsProtons– Positive charge Positive charge
http://videos.howstuffworks.com/hsw/58http://videos.howstuffworks.com/hsw/5806-atomic-structure-the-nucleus-video.h06-atomic-structure-the-nucleus-video.htmtm
NeutronsNeutrons– Neutral chargeNeutral charge
http://videos.howstuffworks.com/hsw/580http://videos.howstuffworks.com/hsw/5807-atomic-structure-neutrons-video.htm7-atomic-structure-neutrons-video.htm
Forces in NucleusForces in Nucleus
Nuclear forcesNuclear forces– Forces that hold nuclear particles Forces that hold nuclear particles
togethertogether– Binds protons and neutrons into the Binds protons and neutrons into the
atomic nucleusatomic nucleus
Sizes of AtomsSizes of Atoms
Based on distance electrons travel away Based on distance electrons travel away from the nucleusfrom the nucleus
http://videos.howstuffworks.com/hsw/5788-http://videos.howstuffworks.com/hsw/5788-size-of-atoms-matter-video.htmsize-of-atoms-matter-video.htm
Counting AtomsCounting Atoms
Atomic NumberAtomic Number– Symbol Symbol Z Z– Number of protons in nucleusNumber of protons in nucleus– The number of protons determines The number of protons determines
identity of the element!!identity of the element!!
Counting AtomsCounting Atoms
IsotopesIsotopes– Atoms of the same element with varying Atoms of the same element with varying
number of neutronsnumber of neutrons– NuclideNuclide – general term for any isotope of – general term for any isotope of
any elementany element– Mass NumberMass Number – total number of protons – total number of protons
+ neutrons+ neutrons
Counting AtomsCounting Atoms
The isotope of hydrogenThe isotope of hydrogen– ProtiumProtium – one proton only; 1e – one proton only; 1e--
– DeuteriumDeuterium – one proton, one neutron, – one proton, one neutron, one electronone electron
– TritiumTritium – one proton, two neutrons, one – one proton, two neutrons, one electron; radioactiveelectron; radioactive
– http://http://www.citycollegiate.com/isotopesofhydrowww.citycollegiate.com/isotopesofhydrogen.htmgen.htm
Counting AtomsCounting Atoms
Designating IsotopesDesignating Isotopes– Hyphen notationHyphen notation
Name-mass #Name-mass #Uranium-235 – How many p, n, e-?Uranium-235 – How many p, n, e-?Ex – Neon with 12 neutrons?Ex – Neon with 12 neutrons?
– Nuclear Symbol NotationNuclear Symbol Notation MNMN
ANAN Element symbolElement symbol
3311HH
2352359292UU
How many p,n,eHow many p,n,e-- in chlorine-37? in chlorine-37?
Relative Atomic MassRelative Atomic Mass
Relative scaleRelative scale– Standard needed to be setStandard needed to be set– Carbon-12Carbon-12
All others compared to Carbon-12All others compared to Carbon-12 Atomic mass unitAtomic mass unit
– amuamu– The mass of an individual atomThe mass of an individual atom– Honors: Approximate mass of a proton Honors: Approximate mass of a proton
or a neutronor a neutron
Average Atomic MassAverage Atomic Mass
Weighted average of the atomic Weighted average of the atomic masses for all known isotopesmasses for all known isotopes– Calculating average atomic mass:Calculating average atomic mass:
Relating mass to the number of Relating mass to the number of atomsatoms
““Particle” – a generic termParticle” – a generic term Mole – SI unit for amount of Mole – SI unit for amount of
substance, counting unitsubstance, counting unit– Symbol – molSymbol – mol– Avogadro’s numberAvogadro’s number
6.02 x 106.02 x 102323 – number of particles – number of particles
in 1mol of substancein 1mol of substance
– Molar massMolar massMass of 1mol of substance – on P.T.Mass of 1mol of substance – on P.T.
ConversionsConversions
Gram Gram Mole Mole Mole Mole Gram Gram Mole Mole Particle Particle Particle Particle Mole Mole Gram Gram Particle Particle Particle Particle Gram Gram
Facts (Conversion Factors):Facts (Conversion Factors):
#g PT = 1 mol#g PT = 1 mol
6.02 x 106.02 x 102323 particles = 1 mol particles = 1 mol