Download Chapter 3: Discovering the Atom and Subatomic Particles

Chapter 3: Discovering the Atom and
Subatomic Particles
3.1 Chemistry Developed Out of Our Interest
in Materials
3.2 Lavoisier Laid the Foundation of Modern
Chemistry
3.3 Dalton Deduced that Matter is Made of
Atoms
3.4 The Electron Was the First Subatomic
Particle Discovered
3.5 The Mass of an Atom is Concentrated in
its Nucleus
3.6 The Atomic Nucleus is Made of Protons
and Neutrons
John Suchocki
© 2011 Pearson Education, Inc.
Chapter 3
2
Humans have tinkered with the materials
around us and used them to our advantage.
• Moldable wet clay – ceramic/pottery fire pits
• 5,000 BC – furnaces (copper ore to metallic
copper
• 1,200 BC – hotter furnaces (iron ores to iron)
• Chinese, Egyptian & Greeks – developed
technology that allowed for mass production
of metal tools and weapons
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Chapter 2
In the 4th century B.C., the influential
Greek philosopher Aristotle described the
composition and behavior of matter in
terms of the four qualities:
hot, cold, dry, and moist.
• Wet clay to ceramic (moist to dry)
• Warm air caused ice to melt (dry to
moist)
• Aristotle’s model held for 2,000 years
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Chapter 2
Fire
Air
Prime
Matter
Water
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Inc.
Chapter
Chapter 2
2
Earth
An alternative view put forth by Democritus (460-370 B.C.)
was the forerunner of our present-day model:
• Matter is composed of a finite number of incredibly small but
discrete units we call atoms.
• Atom from Greek meaning “not cut” or “that which is
indivisible”
• Democritus – texture, mass, color of material were a
function of its atoms
Fe shaped like coils
– strong, malleable
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Atoms of fire were sharp,
lightweight and yellow
Chapter 2
Section 3.2
Lavoisier Laid the
Foundation of Modern
Chemistry
Conceptual Chemistry
John Suchocki
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Chapter 3
2
In the 1436 the printing press was invented in
Europe and there was an information
explosion.
• Robert Boyle (English, 1661) – proposed
that a substance was not an element if it
was made of 2 or more components
Boyle
• Antoine Lavoisier (French, 1778) – “father of
modern chemistry” - identified a compound
as any material composed of 2 or more
elements (required experimentation instead
of logic and reason)
• Lavoisier - Law of mass of conservation –
There is no detectable change in the total
mass of materials when they react
chemically to form new materials.
Lavoisier
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Chapter 2
• Joseph Priestly (English, 1786) – discovered
oxygen which means “acid former”
• Henry Cavendish (English, 1766) – discovered
hydrogen which means “water former”
• Joseph Proust (French, 1790s) – Law of definite
proportions: Elements can combine in definite mass
ratios to form compounds.
Priestly
Proust
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Cavendish
Chapter 2
Section 3.3
Dalton Deduced that
Matter is Made of Atoms
Conceptual Chemistry
John Suchocki
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Chapter 3
2
The 19th century English chemist John Dalton (1766–
1844) reintroduced the atomic ideas of Democritus
through a set of postulates—claims he assumed to be
true based on experimental evidence.
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Chapter 3
Dalton’s Postulates
1. Each element consists of indivisible,
minute particles called atoms.
2. Atoms can be neither created nor
destroyed in chemical reactions.
3. All atoms of a given element are
identical.
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Chapter 3
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Chapter 2
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
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Cu
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Dalton’s Postulates
1. Each element consists of indivisible,
minute particles called atoms.
2. Atoms can be neither created nor
destroyed in chemical reactions.
3. All atoms of a given element are
identical.
4. Atoms chemically combine in
definite whole-number ratios to form
compounds.
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Chapter 3
Dalton’s Postulates
1. Each element consists of indivisible,
minute particles called atoms.
2. Atoms can be neither created nor
destroyed in chemical reactions.
3. All atoms of a given element are
identical.
4. Atoms chemically combine in
definite whole-number ratios to form
compounds.
5. Atoms of different elements have
different masses.
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Chapter 3
Copper
atom
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Oxygen
atom
Chapter
Chapter 3
2
Hydrogen
atom
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Education, Inc.
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Oxygen
atom
Chapter
Chapter 3
2
• Joseph Gay-Lussac (French, 1808) – showed that
gases react in the same way as Proust’s law of
definite proportions – their volumes are in the ratio
of small whole numbers, ie: 2L of H completely
reacts with 1L of O to form 2L of water vapor
• Amadeo Avogadro – (Italian, 1811) – explained that
the fundamental particles of H and O are not atoms
but diatomic molecules (2 atoms per molecule) in
their elemental form
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Chapter 3
• Stanislao Cannizzaro – (Italian, 1858) –
pamphlet at 1st international conference of
chemists (Karlsruhe Meeting) said: Provided
equal volumes of gases contain equal
volumes of atoms or molecules, the relative
masses can be obtained by weighing equal
volumes of gases (at same temperature and
pressure), ie: 1L of O is 16 times heavier than
1L of H so an O molecule is 16 times more
massive than a H molecule.
• Dmitri Mendeleev – (Russian, 1869) –
produced a chart summarizing properties of
known elements (56 elements in 1863) and
predicted that the gaps would be filled in as
the elements were discovered – the Periodic
Table
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Chapter 3
Today, we have high-tech evidence for the particulate
nature of matter. Accumulation of evidence tells us that
atoms are divisible and made of smaller particles called
electrons, protons and neutrons. We call them
subatomic particles.
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Chapter 3
Section 3.4
The Electron Was the First
Subatomic Particle Discovered
Conceptual Chemistry
John Suchocki
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Chapter 3
From afar, a sand dune appears to be made of a
smooth, continuous material. Up close, however, the
dune reveals itself to be made of tiny grains of sand.
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Chapter 2
In a similar fashion, everything around us—no matter
how smooth it may appear—is made of very small
fundamental units you know as atoms.
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Chapter 2
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Chapter 2
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Chapter 2
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© 2011 Pearson Education, Inc.
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© 2011 Pearson Education, Inc.
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© 2011 Pearson Education, Inc.
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© 2011 Pearson Education, Inc.
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© 2011 Pearson Education, Inc.
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© 2011 Pearson Education, Inc.
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© 2011 Pearson Education, Inc.
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© 2011 Pearson Education, Inc.
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© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
© 2011 Pearson Education, Inc.
Chapter 2
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Chapter 2
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Chapter 2
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Chapter 2
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Chapter 2
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Chapter 2
Copper
Atom
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Chapter 2
In 1752, Benjamin Franklin
(1706–1790) learned from
experiments with
thunderstorms that lightning
is a flow of electrical energy
through the atmosphere.
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Chapter 3
In 1752, Benjamin Franklin
(1706–1790) learned from
experiments with
thunderstorms that lightning
is a flow of electrical energy
through the atmosphere.
19th century scientist
experimented to see
whether electrical energy
could pass through a glass
tube evacuated of air.
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Chapter 3
The answer was yes!
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Chapter 3
The cathode ray tube (CRT)
A beam was generated that appeared to behave
as a ray of tiny negatively charged particles.
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Chapter 3
The cathode ray tube (CRT)
Anode – end where + charged particles accumulated
Cathode – end where – charged particles accumulated
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Chapter 3
In 1897, J. J. Thomson
(1856–1940) measured
the deflection angles of
these particles in a
magnetic field.
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Chapter 3
He reasoned that the deflection of the particles depended
on their mass and electric charge.
The greater a particles mass, the greater its resistance to a
change in motion and the smaller the deflection.
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Chapter 3
The greater a particle’s charge, the stronger the magnetic
interactions and therefore the larger the deflection.
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Chapter 3
He reasoned that the deflection of the particles
depended on their mass and electric charge.
Angle
=
Charge
----------------Mass
Knowing only the angle of deflection,
however, Thomson was unable to
calculate either the charge or the mass
of each particle. In order to calculate
the mass, he needed to know the
charge, but in order to calculate the
charge, he needed to know the mass.
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Chapter 3
In 1909, the American
physicist Robert Millikan
(1868–1953) calculated the
numerical value of a single
increment of electric
charge on the basis of the
innovative experiment in
which he sprayed tiny oil
droplets into a specially
designed chamber.
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Chapter 3
The Millikan apparatus
_
+
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Chapter 3
The Millikan apparatus
_
+
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Chapter 3
The Millikan apparatus
_
+
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Chapter 3
The Millikan apparatus
_
+
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Chapter 3
The Millikan apparatus
+
_
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Chapter 3
The Millikan apparatus
+
_
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Chapter 3
What do all these numbers have in common?
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105
20
70
65
35
150
55
10
80
40
95
15
Chapter 3
5
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Chapter 3
-19
1.60 x 10
Coulombs
“The smallest
increment of charge”
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Chapter 3
Millikan calculated the mass of a cathode ray
particle to be considerably less than that of the
smallest known atom, hydrogen.
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Chapter 3
angle
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=
Chapter 3
charge
mass
angle
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=
Chapter 3
charge
mass
mass =
-31
9.1 x 10
kilograms
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Chapter 3
The cathode ray particle is known today as the
electron, a name that comes from the Greek word for
amber (electrik), which is a material the early Greeks
used to study the effects of static electricity.
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Chapter 3
Subatomic particle
electron:
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Chapter 3
Subatomic particle
Electron
mass:
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9.1 x 10
Chapter 3
-31
kg
A 14 inch cathode ray tube showing its deflection coils and electron guns
The cathode ray – stream of electrons – is used in
traditional TVs
A cathode ray tube with one end widened into a
phosphor-coated screen.
Signals from the TV station cause electrically charged
plates in the tube to control the direction of the ray so
that images are traced onto the screen.
A 14 inch cathode ray tube
showing its deflection coils
and electron guns
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Chapter 3
Section 3.5
The Mass of an Atom Is
Concentrated in its Nucleus
Conceptual Chemistry
John Suchocki
© 2011 Pearson Education, Inc.
Chapter 3
Around 1910, the New
Zealand physicist Ernest
Rutherford (1871–1937)
oversaw the now-famous
gold-foil experiment,
which was the first
experiment to show that
the atom is mostly empty
space and that most of its
mass is concentrated in a
tiny central core called the
atomic nucleus.
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Chapter 3
Gold
Foil
Experiment
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Chapter 3
Alpha
particles
Deflected
particles
Source
Gold
foil
Screen
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Education,
Inc.
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Education,
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Chapter
43
Chapter
Undeflected
particles
Gold
foil
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Chapter 3
Atomic
nucleus
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Chapter 4
Atomic
nucleus
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Chapter 3
Electron
cloud
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Atomic
nucleus
Chapter 3
Section 3.6
The Atomic Nucleus Is Made of
Protons and Neutrons
Conceptual Chemistry
John Suchocki
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Chapter 3
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Chapter 3
Atomic
nucleus
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Chapter 3
Electron
“cloud”
Atomic
nucleus
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Chapter 3
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Chapter 3
Atomic
nucleus
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Chapter 3
Proton
Neutron
Atomic
nucleus
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Chapter 3
Nucleons
Proton
Neutron
Atomic
nucleus
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Chapter 3
In 1932, the British physicist
James Chadwick (1891–
1974) detected the nucleus.
The neutron has the same
mass as the proton but is has
no electric charge –
“electrically neutral”. Both
protons and neutrons are
located in the atomic nucleus
and are called nucleons.
Won the Nobel Prize in
physics in 1935 for his
discovery.
Assisted as an advisor to the
Manhattan Project
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Chapter 3
Subatomic
Particle
Electron
Proton
Neutron
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Chapter 3
Subatomic
Particle
Nucleons
Electron
Proton
Neutron
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Chapter 3
Subatomic
Particle
Nucleons
Electron
Proton
“Atom.mov”
Neutron
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Chapter 3
Subatomic
Particle
Nucleons
Electron
Proton
Neutron
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Chapter 3
Subatomic
Particle
Nucleons
Electron
Proton
Neutron
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Chapter 3
Subatomic
Particle
Nucleons
Electron
Proton
Neutron
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Chapter 3
Subatomic
Particle
Nucleons
Electron
Proton
Neutron
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Chapter 3
Nucleons
Subatomic
Particle
Charge
Electron
-1
Proton
+1
Neutron
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0
Chapter 3
Nucleons
Subatomic
Particle
Charge
Relative
Mass
Electron
-1
1
Proton
+1
1836
0
1841
Neutron
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Chapter 3
Atomic number
The number of protons
each atom of a given
element contains
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Chapter 3
The Periodic Table
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Chapter 3
Atomic Number
Isotopes
Atoms of the same
element that contain
different numbers of
neutrons
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Chapter 3
Hydrogen
protium
deuterium
tritium
These atoms are
“isotopes” of one another
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Chapter 3
Mass number
The total number of
nucleons an atom
contains
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Chapter 3
Hydrogen, H
H-1
H-2
H-3
Mass numbers
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Chapter 3
Iron, Fe
Fe-55
Fe-56
Mass numbers
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Chapter 3
Iron, Fe
Fe-55
Fe-56
55 nucleons
26 protons
29 neutrons
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Chapter 3
Iron, Fe
Fe-55
Fe-56
56 nucleons
26 protons
30 neutrons
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Chapter 3
Mass number
56
26
Fe
Atomic number
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Chapter 3
Nucleons
56
26
Fe
Protons
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Chapter 3
What is atomic mass?
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Chapter 3
Carbon-12
Carbon-13
Carbon-14
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Chapter 3
Percent
Abundance
Carbon-12
99%
Carbon-13
1%
Carbon-14
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Chapter 3
< 0.0000001%
Percent
Abundance
Carbon-12
99%
Carbon-13
1%
Carbon-14
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Chapter 3
< 0.0000001%
Percent
Abundance
Carbon-12
99%
Carbon-13
1%
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Chapter 3
Percent
Abundance
Carbon-12
99 out of 100
Carbon-13
1 out of 100
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Chapter 3
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Chapter 3
The average
“atomic mass” of any
macroscopic sample
of carbon is slightly
more than 12.
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Chapter 3
Carbon
Atomic mass = 12.011
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Chapter 3
Atomic mass
The average mass of
all the isotopes of an
element
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Chapter 3
Atomic
mass
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Chapter 3
Carbon
Atomic mass = 12.011
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Chapter 3
Carbon
Atomic mass = 12.011
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Chapter 3
Carbon
Atomic mass = 12.011 amu
“Atomic mass units”
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Chapter 3
Atomic mass unit
conversion factor
-24
1 amu = 1.661 x 10
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Chapter 3
gram