Ch. 4: Atomic Structure 4.1 Defining the Atom. History Democritus named the most basic particle...

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Ch. 4: Atomic Ch. 4: Atomic Structure Structure 4.1 Defining the Atom 4.1 Defining the Atom

Transcript of Ch. 4: Atomic Structure 4.1 Defining the Atom. History Democritus named the most basic particle...

Page 1: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Ch. 4: Atomic StructureCh. 4: Atomic Structure

4.1 Defining the Atom4.1 Defining the Atom

Page 2: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

HistoryHistory

DemocritusDemocritus named the most basic named the most basic

particleparticle atomatom- means “indivisible”- means “indivisible”

AristotleAristotle didn’t believe in atomsdidn’t believe in atoms thought matter was thought matter was

continuouscontinuous

Page 3: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

HistoryHistory

by 1700s, all chemists agreed:by 1700s, all chemists agreed: on the existence of atomson the existence of atoms that atoms combined to make compoundsthat atoms combined to make compounds

Still did not agree on whether elements Still did not agree on whether elements combined in the same ratio when making combined in the same ratio when making a compounda compound

Page 4: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Dalton’s Atomic Theory-1803Dalton’s Atomic Theory-1803

1. Matter is made of small, indivisible particles 1. Matter is made of small, indivisible particles called atomscalled atoms

2. Atoms of same element have the same size, 2. Atoms of same element have the same size, mass, and propertiesmass, and properties

3. Atoms of different element combine in whole 3. Atoms of different element combine in whole number ratios to make compounds. number ratios to make compounds.

4. In chemical reactions, atoms are combined, 4. In chemical reactions, atoms are combined, separated, and rearranged.separated, and rearranged.

Page 5: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Consequences of Dalton’s TheoryConsequences of Dalton’s Theory

The “billiard ball model”-The “billiard ball model”-the atom the atom is viewed as a small solid indivisible sphere. is viewed as a small solid indivisible sphere. 

Some parts of Dalton’s theory were wrong:Some parts of Dalton’s theory were wrong: atoms are divisible into smaller particles (subatomic atoms are divisible into smaller particles (subatomic

particles)particles) atoms of the same element can have different atoms of the same element can have different

masses (isotopes)masses (isotopes) Most important parts of atomic theory:Most important parts of atomic theory:

all matter is made of atomsall matter is made of atoms atoms of different elements have different propertiesatoms of different elements have different properties

Page 6: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Law of Conservation of MassLaw of Conservation of Mass

mass is neither created or destroyed mass is neither created or destroyed during regular chemical or physical during regular chemical or physical changeschanges

Page 7: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Law of Definite ProportionsLaw of Definite Proportions

any amount of a compound contains the any amount of a compound contains the same element in the same proportions by same element in the same proportions by mass mass

No matter where the copper carbonate is used, it still has the same composition

Page 8: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Law of Multiple ProportionsLaw of Multiple Proportions applies when 2 or more elements combine to applies when 2 or more elements combine to

make more than one type of compoundmake more than one type of compound the mass ratios of the second element simplify to the mass ratios of the second element simplify to

small whole numberssmall whole numbers

Page 9: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Ch. 4: Atomic StructureCh. 4: Atomic Structure

4.2 Structure of Atom4.2 Structure of Atom

Discovery of the subatomic Discovery of the subatomic particlesparticles

Page 10: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Discovery of ElectronDiscovery of Electron resulted from scientists (JJ Thompson) passing electric resulted from scientists (JJ Thompson) passing electric

current through gases to test conductivitycurrent through gases to test conductivity

used used cathode-ray tubes cathode-ray tubes noticed that when current was passed through a noticed that when current was passed through a

tube a glow (or “ray”) was producedtube a glow (or “ray”) was produced

Page 11: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Discovery of Discovery of ElectronElectron

Noted Qualities of Ray Produced:Noted Qualities of Ray Produced:

1.1. existedexisted-- there was a shadow on the there was a shadow on the glass when an object was placed insideglass when an object was placed inside

2.2. had had massmass-- the paddle wheel placed the paddle wheel placed inside, moved from one end to the other inside, moved from one end to the other so something must have been “pushing” so something must have been “pushing” itit

Page 12: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Discovery of ElectronDiscovery of ElectronNoted Qualities of Ray Produced:Noted Qualities of Ray Produced:

3.3. negatively chargednegatively charged-- the rays were attracted to the rays were attracted to the positive pole (anode)- opposites attract!the positive pole (anode)- opposites attract!

Page 13: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Discovery of ElectronDiscovery of Electron

Conclusion:Conclusion:

there were negatively charged there were negatively charged particles inside the cathode rayparticles inside the cathode ray

The particle was called The particle was called ELECTRONELECTRON

Cathode rays are made of electronsCathode rays are made of electrons

Page 14: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Discovery of ElectronDiscovery of Electron

J.J. ThomsonJ.J. Thomson (English 1897) did more (English 1897) did more experiments to actually make the experiments to actually make the discoverydiscovery

he found ratio of charge to mass of this he found ratio of charge to mass of this particleparticle

since the ratio stayed constant for any since the ratio stayed constant for any metal that contained it, it must be the metal that contained it, it must be the same in all of the metalssame in all of the metals

Page 15: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Plum Pudding Model (1897Plum Pudding Model (1897))   proposed by Joseph John Thomson proposed by Joseph John Thomson Nobel Prize in physics in 1906Nobel Prize in physics in 1906 the atom was a the atom was a sphere of positive sphere of positive

electricity (which was diffuse) with electricity (which was diffuse) with negative particles (electrons) imbedded negative particles (electrons) imbedded throughoutthroughout

Page 16: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Charge and mass of electronCharge and mass of electron

1916- Robert Millikan1916- Robert Millikan

discovered the charge and the mass of discovered the charge and the mass of the electronthe electron

Electron has Electron has a charge of -1a charge of -1 a mass of 1/ 1840 of the mass of a mass of 1/ 1840 of the mass of

Hydrogen atom (the smallest atom)Hydrogen atom (the smallest atom)

Page 17: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Are electrons the only particles?Are electrons the only particles?

since atoms are neutral, something must since atoms are neutral, something must balance the negative chargebalance the negative charge

since an atom’s mass is so much larger since an atom’s mass is so much larger than the mass of its electrons, there must than the mass of its electrons, there must be other matter inside an atombe other matter inside an atom

Page 18: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Canal raysCanal rays

1886 Goldstein1886 Goldstein In the cathode tube experiment Goldstein In the cathode tube experiment Goldstein

noticed another rays traveling from anode noticed another rays traveling from anode to cathodeto cathode

He named those rays He named those rays canal rayscanal rays and are and are made of positive particles called made of positive particles called protonsprotons

Page 19: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Discovery of NucleusDiscovery of Nucleus

Rutherford discovered the Rutherford discovered the nucleus nucleus by shooting by shooting alpha particles (have positive charge) at a very alpha particles (have positive charge) at a very thin piece of gold foilthin piece of gold foil

1911- Ernest Rutherford- the gold foil 1911- Ernest Rutherford- the gold foil experimentexperiment

he predicted that the particles would go right he predicted that the particles would go right through the foil at some small anglethrough the foil at some small angle

Page 20: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Discovery of NucleusDiscovery of Nucleus

Page 21: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Discovery of NucleusDiscovery of Nucleus some particles (1/8000) bounced back some particles (1/8000) bounced back

from the foilfrom the foil this meant there must be a “powerful this meant there must be a “powerful

force” in the foil to hit particle backforce” in the foil to hit particle back

Predicted Results Actual Results

Page 22: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Discovery of NucleusDiscovery of NucleusCharacteristics of Characteristics of

““Powerful Force”:Powerful Force”:1.1. dense-dense- since it was strong since it was strong

enough to deflect particleenough to deflect particle2.2. small-small- only 1/8000 hit the force only 1/8000 hit the force

dead on and bounced backdead on and bounced back3.3. positively charged-positively charged- since there since there

was a repulsion between force was a repulsion between force and alpha particles and alpha particles

4.4. ““Powerful Force”= NucleusPowerful Force”= Nucleus

Page 23: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

The Nuclear Model- The Nuclear Model- proposed byproposed by Ernest Ernest RutherfordRutherford

the atom is mostly empty space with a the atom is mostly empty space with a dense positively charged dense positively charged nucleus nucleus surrounded by negative electronssurrounded by negative electrons.  . 

Rutherford received the Nobel Prize in Rutherford received the Nobel Prize in chemistry in 1908 for his contributions chemistry in 1908 for his contributions into the structure of the atom. into the structure of the atom. 

Page 24: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

The discovery of NeutronsThe discovery of Neutrons

1932- Chadwick1932- Chadwick

Neutrons have NO CHARGENeutrons have NO CHARGE Neutrons have the mass almost equal to Neutrons have the mass almost equal to

the protonthe proton

Page 25: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Structure of AtomStructure of Atom

Nucleus:Nucleus: contains protons and contains protons and

neutronsneutrons takes up very little takes up very little

spacespace

Electron Cloud:Electron Cloud: contains electronscontains electrons takes up most of takes up most of

spacespace

Page 26: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Subatomic ParticlesSubatomic Particles

includes all particles inside atomincludes all particles inside atom protonproton electronelectron neutronneutron

charge on protons and electrons are equal charge on protons and electrons are equal but oppositebut opposite

to make an atom neutral, need equal to make an atom neutral, need equal numbers of protons and electronsnumbers of protons and electrons

Page 27: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Subatomic ParticlesSubatomic Particles

number of protons identifies the atom as a number of protons identifies the atom as a certain elementcertain element

protons and neutrons are about same sizeprotons and neutrons are about same size electrons are much smaller electrons are much smaller nuclear forcenuclear force- when particles in the nucleus get - when particles in the nucleus get

very close, they have a strong attractionvery close, they have a strong attraction proton + protonproton + proton proton + neutronproton + neutron neutron + neutronneutron + neutron

Page 28: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

The Subatomic ParticlesThe Subatomic Particles

ParticleParticle SymbolSymbol ChargeCharge Relative Relative MassMass

ElectronElectron e-e- -1-1 1/18401/1840

ProtonProton p+p+ +1+1 11

NeutronNeutron n n 00 00 11

Page 29: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Ch. 4 Atomic StructureCh. 4 Atomic Structure

4.3 Distinguishing among Atoms4.3 Distinguishing among Atoms

Page 30: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Atomic structureAtomic structureAtomic number ZAtomic number Z

Z= atomic number= # protons= # electronsZ= atomic number= # protons= # electrons

Indicates the position of the element in the periodic Indicates the position of the element in the periodic table (the whole number by each element)table (the whole number by each element)

Ex: Ex: 66C , C , 1919 K, K, 11HHMass number AMass number A

A= # protons + # neutronsA= # protons + # neutrons

To find A round up the decimal number for each To find A round up the decimal number for each element in the Periodic tableelement in the Periodic table

Ex: Ex: 1212C, C, 3939K, K, 11H or C-12, K-39, H-1H or C-12, K-39, H-1

Page 31: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

How to calculateHow to calculate

A. electrons= atomic number ZA. electrons= atomic number Z

B. protons= atomic number ZB. protons= atomic number Z

C. C. neutrons= mass number – atomic numberneutrons= mass number – atomic number

n= A-Zn= A-Z

Page 32: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

ISOTOPESISOTOPES

Members of the same familyMembers of the same family Have Have the samethe same chemical symbolchemical symbol

number of protons number of protons number of electronsnumber of electronsatomic numberatomic number

Have Have different different mass numbersmass numbers

numbers of neutronsnumbers of neutrons

Ex: Ex: 1212C, C, 1313C, C, 1414C, C, 1616C- all have 6 electrons and 6 C- all have 6 electrons and 6 protons but 6, 7, 8, and 10 neutronsprotons but 6, 7, 8, and 10 neutrons

Page 33: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Relative Atomic MassRelative Atomic Mass

since masses of atoms are so small, it is since masses of atoms are so small, it is more convenient to use relative atomic more convenient to use relative atomic masses instead of real massesmasses instead of real masses

to set up a scale, we have to pick one to set up a scale, we have to pick one atom to be the standardatom to be the standard

since 1961, the carbon-12 nuclide is the since 1961, the carbon-12 nuclide is the standard and is assigned a mass of standard and is assigned a mass of exactly 12 amuexactly 12 amu

Page 34: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Relative Atomic MassRelative Atomic Mass

atomic mass unit (amu)- one is exactly atomic mass unit (amu)- one is exactly 1/121/12thth of the mass of a carbon-12 atom of the mass of a carbon-12 atom

mass of proton= 1.007276 amumass of proton= 1.007276 amu mass of neutron= 1.008665 amumass of neutron= 1.008665 amu mass of electron= 0.0005486 amu mass of electron= 0.0005486 amu

Page 35: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Relative Atomic MassRelative Atomic Mass

the mass number (A) and the relative the mass number (A) and the relative atomic mass are very close but not the atomic mass are very close but not the same becausesame because relative atomic mass includes electronsrelative atomic mass includes electrons the proton and neutron masses aren’t exactly the proton and neutron masses aren’t exactly

1 amu1 amu

Page 36: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Average Atomic MassAverage Atomic Mass

weighted relative atomic masses of the weighted relative atomic masses of the isotopes of each elementisotopes of each element

Is the Is the decimal numberdecimal number found in each box found in each box for each element in the Periodic tablefor each element in the Periodic table

Page 37: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Average Atomic MassAverage Atomic Mass

To calculate it we need to know: To calculate it we need to know: number of isotopesnumber of isotopes Mass of each isotopeMass of each isotope Percentage (relative abundance) of each Percentage (relative abundance) of each

isotope)isotope)

Page 38: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Calculating Average Atomic MassCalculating Average Atomic Mass

Naturally occurring copper consists of:Naturally occurring copper consists of: 69.71% copper-63 (62.929598 amu)69.71% copper-63 (62.929598 amu) 30.83% copper-65 (64.927793 amu)30.83% copper-65 (64.927793 amu)

(0.6971 x 62.929598)+(0.3083 x 64.927793)(0.6971 x 62.929598)+(0.3083 x 64.927793)

=63.55 amu=63.55 amu

Page 39: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Calculating Average Atomic MassCalculating Average Atomic Mass

An element has three main isotopes with An element has three main isotopes with the following percent occurances:the following percent occurances: #1: 19.99244 amu, 90.51%#1: 19.99244 amu, 90.51% #2: 20.99395 amu, 0.27%#2: 20.99395 amu, 0.27% #3: 21.99138 amu, 9.22%#3: 21.99138 amu, 9.22%

Find the average atomic mass and Find the average atomic mass and determine the element.determine the element.

Page 40: Ch. 4: Atomic Structure 4.1 Defining the Atom. History  Democritus named the most basic particle named the most basic particle atom- means “indivisible”

Calculating Average Atomic MassCalculating Average Atomic Mass

amu17945.20

100

9.22)(21.99138 0.27)(20.99395x 90.51)(19.99244x

Neon