atomic sructure 2
TRANSCRIPT
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Atoms and Atomic
Structure
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Law of Conservation of MassLavoisier (1743-1794)
In a chemical reaction, matter is neither created
nor destroyed.
P. 57
Click on picture for movie
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CuCO3(s) CuO(s) + CO2(g)
123.6 g 79.6 g ? g
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CuCO3(s) CuO(s) + CO2(g)
123.6 g 79.6 g 44.0 g
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CuCO3(s) CuO(s) + CO2(g)
123.6 g 79.6 g 44.0 g
. . .=
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Law of Definite ProportionsProost (1754-1826)
Different samples of any pure compound containthe same elements in the same proportions by
P. 58
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Mass Ratio of Cu:O:C in copper carbonate
Cu:O:C = 53:40:10 = 5.3 : 4: 1
Regardless of where the copper carbonateis found
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Mass Ratio of Cu:O:C in copper carbonate
Cu:O:C = 53:40:10 = 5.3 : 4: 1
If a sample of copper carbonate contains20 g of carbon how many g of Cu will it
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Mass Ratio of Cu:O:C in copper carbonate
Cu:O:C = 53:40:10 = 5.3 : 4: 1
If a sample of copper carbonate contains20 g of carbon how many g of Cu will it
(5.3g / 1g)20g = x
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Mass Ratio of Cu:O:C in copper carbonate
Cu:O:C = 53:40:10 = 5.3 : 4: 1
If a sample of copper carbonate contains20 g of carbon how many g of Cu will it
106 g = x
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Law of Multiple Proportions(John Dalton)
The masses of one element that can combinechemically with a fixed mass of another
2C + O2 2CO Carbon monoxide
C + O2 CO2 Carbon dioxide
P. 59
24 g 32 g
12 g 32 g
2:1
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The idea of whole numbers
suggests the presence ofindividual particle
ATOMS !
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Daltons Atomic Theory
John Dalton (1766-1844) proposed an atomic theory
1. matter is composed, indivisible particles (atoms).2. all atoms of a particular element are identical3. different elements have different atoms
- .
5. In a chemical reaction, atoms are merelyrearranged to form new compounds; they are notcreated, destroyed, or changed into atoms of any
other elements.
P. 56-57
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OK! Matter is made of ATOMS
But what are ATOMS?
What are ATOMS themselves
made of?
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CathodeRay Tube
P. 61
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J.J. Thompson
(1856-1940)
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Cathode Rays - JJ Thompson
P. 62
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Mass of an electron Experiments performed by Thompson
together with those of Robert Millikan were
able to show that an electron has a mass of
9.1 x 10-28 g
The mass of one atom of the lightestelement, hydrogen, is 1.7 x 10-24 g
An electron is approx 1/2000th the mass of
a H atom!
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So the electron appears to be an
insignificant part of the atom -from a mass point of view!
How are electrons arranged
inside an atom?
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Thompsons Plum PuddingModel of the Atom
electronuse pos ve
charge
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Ernest Rutherford
(1871-1937)
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Nucleus of the AtomRutherford (1871-1937)
P. 64Click on picture for movie
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Nucleus of the Atom Continued
P. 64
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Nucleus of the Atom Continued(Rutherford)
At the center of the atom is a very dense nucleus thataccounts for almost all the mass of the atom and
contains all the positive charge.He named these positive particles protons.
Protons have a relative mass of 1 and a charge of +1.
P. 64
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Nucleus of the AtomChadwick (1891-1974)
When atoms of beryllium were bombardedwith alpha particles, new uncharged particles
.
These uncharged particles were calledneutrons.
Neutrons have a relative mass of 1 and acharge of zero.
P. 64-65
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Characteristics of the Three Basic
Subatomic Particles
P. 65
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Arrangement of SubatomicParticles in the Atom
P. 66
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SPACE !
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And so are ALL OF US !
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Our first direct look at the atomicworld
Get me out of here!
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View of Atoms from STM
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Scanning Tunneling Microscopy
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Isotopes
Atoms of an element that have the same number of
protons but different numbers of neutrons are calledisotopes.
Z A = mass number
Z = atomic number
The isotopes of sulfur are written:32
S33
S34
S36
S16 16 16 16
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Isotopes Continued
Which of the following represent isotopes of the
same element? Which element?
234
X234
X235
X238
X92 93 92 92
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Answer:
234 234 235 238
92 93 92 92
234
Npis not an isotope of Uranium.
93
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Isotopes of Carbon
12 13 14
6 6 6
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12 13 14
Isotopes of Carbon
6 6 6
12 - 6 = 6neutrons
13 - 6 = 7neutrons
14 - 6 = 8neutrons
Radioactive
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Carbon-14 Dating
Used to date archeological artifacts up to60000 years old
14
sample
Amount of 14C decreases with time
will be discussed in detail in Ch 5
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Isotopic Fingerprinting
The ratio of stable isotopes (e.g.13
C/12
C) ina substance will vary slightly depending on
the ori in of the substance
for example, petroleum samples fromdifferent parts of the world will have
different 13C/12C ratios
How could such information be useful?
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Time for some nuclear chemistry
lets begin Ch 5
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Periodic Table
Mendeleev (1834-1907)
Horizontal rows called periods
Vertical columns called groups
Elements within a group have similar chemicalproperties
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The Periodic Table
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Properties of Alkali Metals andHalogens
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Metals
Metals have distinctive properties
Good conductors of heat and electricityShiny appearance
Ductile and malleable
Are light purple in periodic table that is on the
inside cover of the book
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Nonmetals
Do not conduct heat or electricity
Not ductile or malleableMany exist as gases
Are green in periodic table that is on the inside
cover of the book
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Semimetals
Have properties that lie between those of
metals and nonmetalsAre gold yellow in the periodic table that is on
the inside cover of the book
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REFERENCE
www.langara.bc.ca/chemistry/A_Mosi/C1117_Ch3.ppt