Adv Chem Pp03
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Transcript of Adv Chem Pp03
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Chapter 3
Atoms and Moles
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Atomic Models
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3.1 Matter Made of Atoms
Atomic Theory
Mikhail Lomonosov (1711-1795)and Antoine Lavosier (1743-1794): developed law ofconservation of mass
states that mass of reactants
equals mass of products
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Law of Conservation of Mass
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Law of Conservation of Mass
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3.1 Matter Made of Atoms
Atomic Theory
Joseph Proust (1754-1826):proposed law of definiteproportions
states that two samples of agiven compound are made of
the same elements in exactlythe same proportions by mass
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3.1 Matter Made of Atoms
Atomic Theory
Claude-Louise Berthollet (1748-1822): proposed law ofmultiple proportions
states that when twoelements combine to form two
or more compounds, the massof one element that combineswith a mass of the other is in
the ratio of small whole #s
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3.1 Matter Made of Atoms
Daltons Atomic Theory
John Dalton (1766-1844):developed a new atomic theory
1. all matter is made of atoms,which cannot be subdivided,created, or destroyed
2. atoms of a given elementare identical in their chemicaland physical properties
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3.1 Matter Made of Atoms
Daltons Atomic Theory
3. atoms of different elementsdiffer in their physical andchemical properties
4. atoms of different elementscombine in simple, whole-
number ratios to formcompounds
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3.1 Matter Made of Atoms
Daltons Atomic Theory
5. in chemical reactions,atoms are combined,separated, or rearranged butnot created, destroyed, orchanged
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3.1 Matter Made of Atoms
Further Progress
Jons Berzelius (1779-1848)
studied proportions in which
elements combine with oneanother (over 2000)
experimental underpinning
of Daltons theorymade table of atomic weights
named halogens
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3.1 Matter Made of Atoms
Further Progress
Jons Berzelius (1779-1848)
invented alphabetical
nomenclature of elementscoined terms organicchemistry, catalysis, and
protein
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3.1 Matter Made of Atoms
Further Progress
valency and bonding describedin 1850s
Stanislao Cannizzaro(remember?): distinctionbetween atoms and molecules
periodic table developed in1860s
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3.2 Structure of Atoms
Subatomic Particles
Heinrich Geissler (1814-1879):invented the vacuum tube (late1850s)
vacuum tube: hollow, glasstube in which the air has been
removed; electrodes at eitherend
produces a glow when current
flows between electrodes
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3.2 Structure of Atoms
Subatomic Particles
Eugen Goldstein (1850-1930)
named glowing rays cathode
rays (1876)showed that they weredeflected by magnetic fields;
could cast shadowsdiscovered rays coming fromanode; called them canal
rays (1886)
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3.2 Structure of Atoms
Subatomic Particles
William Crookes (1832-1919)
showed that cathode rays
were made of particles, notlight (1879)
convincing to the British, but
not mainlanders
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3.2 Structure of Atoms
Subatomic Particles
J. J. Thomson (1856-1940):showed that rays were slowerthan light (1894)
Jean Perrin (1870-1942):showed that metal plates hit by
rays became negatively charged(1895)
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Three Random Walks
f
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3.2 Structure of Atoms
Subatomic Particles
J. J. Thomson (again)
measured mass/charge; found
that particles were small orcharge was large (1897)
measured electric charge
itself; found electrons to be1/2000 mass of a H atom(1899)
new atomic model
fl f h d
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Deflections of Cathode Rays
h i d l
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Thomsons Atomic Model
3 2 S f A
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3.2 Structure of Atoms
Subatomic Particles
Ernest Rutherford (1871-1937)
discovered and radiation
(1890s)discovered radiation (1900)
discovered that particles are
a He nucleus (1908)
R di ti
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, , Radiation
R di ti I
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Radiation Image
3 2 St t f At
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3.2 Structure of Atoms
Subatomic Particles
Ernest Rutherford (1871-1937)
gold foil experiment (1909)
particles fired at gold foil
most went through, somedeflected
conclusion: most of themass and charge of anatom is in the nucleus;electrons in cloud
G ld
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Gold
G ld F il E i t
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Gold Foil Experiment
E t ti R lit
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Expectations versus Reality
E l ti
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Explanation
E l ti
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Explanation
R th f d P
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Rutherfords Paper
3 2 St ct e of Atoms
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3.2 Structure of Atoms
Subatomic Particles
Francis Aston (1877-1945):showed that atoms come indifferent varieties (differentweights) (1912)
called isotopes: atoms with
the same number of protonsbut different numbers ofneutrons
E.R. discovered proton (1918)
Evidence for Isotopes
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Evidence for Isotopes
3 2 Structure of Atoms
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3.2 Structure of Atoms
Subatomic Particles
James Chadwick (1891-1974):discovered the neutron (sort of)(1932)
3 3 Electron Configuration
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3.3 Electron Configuration
Electrons and Light
Light as a moving wave
c= f
c speed of light = 3 x 108
m/s
wavelength (m)
distance between peak ortroughs of a wave
f frequency (1/s 1 hertz) # of waves er second
Waves
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Waves
Light Waves
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Light Waves
Light
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Light
3 3 Electron Configuration
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3.3 Electron Configuration
Electrons and Light
Albert Einstein (1879-1955)
atoms emit or absorb EMradiation in discrete(quantized) units (1905)
light has properties of waves
and particles (1905)
3 3 Electron Configuration
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3.3 Electron Configuration
Electrons and Light
Niels Bohr (1885-1962)
worked with Rutherford
new atomic model: electronsorbit nucleus at particularenergy levels (1912)
electrons dont give off energy(no spiraling allowed)
Why dont electrons go
strai ht to the nucleus???
3 3 Electron Configuration
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3.3 Electron Configuration
Electrons and Light
Bohrs model
electron in state of lowestpossible energy is in groundstate
if electron gains energy, it
moves to an excited state(!)if electron falls back to groundstate, it releases energy as
light
Excited State
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Excited State
Absorbance and Emission
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Absorbance and Emission
Absorbance and Emission
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Absorbance and Emission
Quantization
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Quantization
3 3 Electron Configuration
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3.3 Electron Configuration
Electrons and Light
Bohrs model, continued
Bohr predicted thewavelengths of light forhydrogenhe was right!
all light wavelengths together
are called line-emissionspectrum
each element has its own
Hydrogen Emission
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Hydrogen Emission
H Absorbance and Emission
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H Absorbance and Emission
3 3 Electron Configuration
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3.3 Electron Configuration
Electrons and Light
Louis de Broglie (1892-1987)
particles can be described aswaves (1925)
therefore, electrons can onlyhave certain frequencies
(energy levels) and cant falltoward nucleus
quantum atomic model
3 3 Electron Configuration
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3.3 Electron Configuration
Quantum numbers
n principal (main energylevels)
l angular momentum (shapeor type of sublevel)
l= 0 sorbital
l= 1 porbitall= 2 dorbital
l= 3 forbital
Principal Quantum Number
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Principal Quantum Number
Energy Level Transitions
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Energy Level Transitions
3 3 Electron Configuration
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3.3 Electron Configuration
Quantum numbers
ml magnetic (subset oflquantum number)
ms spin (orientation of
magnetic field) +1/2 or -1/2
Quantum Numbers
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Quantum Numbers
Orbital Shapes
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Orbital Shapes
3 3 Electron Configuration
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3.3 Electron Configuration
Electron Configurations
Pauli exclusion principle:each orbital can hold no morethan two electrons
no two electrons can have thesame four quantum numbers
Aufbau principle: electrons fillorbitals that have the lowestenergy first
1s
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Overlapping Orbital Energies
3 3 Electron Configuration
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3.3 Electron Configuration
Electron Configurations
Hunds rule: orbitals of thesame nand lnumber areoccupied by one electron before
pairing occurs
Hunds Rule
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Hund s Rule