General Chemistry

1. How is the structure ofHow is the structure of
the atom related to itsthe atom related to its
behavior?behavior?
Chemistry 1: Unit 3Chemistry 1: Unit 3

2. Main IdeasMain Ideas
The ancient Greeks tried to explain matter,
but the scientific study of the atom began
with John Dalton in the early 1800's.
An atom is made of a nucleus containing
protons and neutrons; electrons move
around the nucleus.
The number of protons and the mass
number define the type of atom.
Unstable atoms emit radiation to gain
stability.

3. Objectives:
•Compare and contrast the atomic models
of Democritus, Aristotle, and Dalton.
• Understand how Dalton's theory explains
the conservation of mass.
3:1 Early Ideas about Matter3:1 Early Ideas about Matter

4. Early Greek Philosophers
Many ancient scholars believed matter was
composed of such things as earth, water,
air, and fire.
• Many believed
matter could be
endlessly divided
into smaller and
smaller pieces.

5. • Democritus (460–370 B.C.) was the first
person to propose the idea that matter was
not infinitely divisible, but made up of
individual particles called atomos.
DemocritusDemocritus

6. DemocritusDemocritus

7. AristotleAristotle
Aristotle (484–322 B.C.) disagreed with
Democritus because he did not believe empty
space could exist.
Aristotle’s views went unchallenged for
2,000 years until science developed
methods to test the validity of his ideas.

8. Greek PhilosophersGreek Philosophers

9. Democritus vs. AristotleDemocritus vs. Aristotle
It was difficult for Democritus to defend his
ideas because controlled experiments on his
theory were not possible.

10. John DaltonJohn Dalton
(English school teacher -1766-1844)(English school teacher -1766-1844)
Responsible for the beginning of theResponsible for the beginning of the
development of modern atomic theory. Daltondevelopment of modern atomic theory. Dalton
revised Democritusrevised Democritus’s theories by performing’s theories by performing
and studying many chemical reactions.and studying many chemical reactions.
Through careful observations andThrough careful observations and
measurements he was able to determine massmeasurements he was able to determine mass
ratios of the elements involved in thoseratios of the elements involved in those
reactions.reactions.

11. • John Dalton revived the idea of the
atom in the early 1800s based on
numerous chemical reactions.
• Dalton’s atomic theory easily explained
conservation of mass in a reaction as the
result of the combination, separation, or
rearrangement of atoms.
John DaltonJohn Dalton

12. DaltonDalton’s Atomic Theory’s Atomic Theory
Even though some of the theory was incorrect, It
provided the basis we have today for atomic theory.
As is common with science, his theory has since
been revised and additional information learned.

13. DaltonDalton’s Atomic Theory’s Atomic Theory
Which parts of DaltonWhich parts of Dalton’s Atomic Theory’s Atomic Theory
was incorrect?was incorrect?
1. Atoms are indivisible.
2. Atoms of a given element are
identical in size, mass and chemical
properties.

14. Question ?Question ?
Who was the first person to propose the
idea that matter was not infinitely
divisible?
A. Aristotle
B. Plato
C. Dalton
D. Democritus

15. Dalton’s theory also conveniently
explained what?
A. the electron
B. the nucleus
C. law of conservation of mass
D. law of Democritus
Question?Question?

16. • Define atom.
• Distinguish between the subatomic
particles in terms of relative charge and
mass.
• Describe the structure of the atom,
including the locations of the subatomic
particles.
3:2 Defining the Atom3:2 Defining the Atom
ObjectivesObjectives

17. The smallest particle of an element that
retains the properties of the element is
called an atom.
• An instrument called the scanning
tunneling microscope (STM) allows
individual atoms to be seen.
• Gerd Binnig and Heinrich Rohrer won
the Nobel Prize in 1986 for the
invention of the STM
The AtomThe Atom

18. STMSTM

19. Scanning tunneling
microscopy (STM) is the
highest resolution imaging
and nanofabrication
technique available. It relies
on quantum tunneling of
electrons from a sharp
metal tip to a conducting
surface. The 71 Angstrom
diameter "quantum corral"
shown above was created
and imaged with an ultra-
high vacuum cryogenic
STM. Each sharp peak in
the circle is an iron atom
resting on atomically flat
copper
STMSTM

20. When an electric charge is applied, a
ray of radiation travels from the cathode
to the anode, called a cathode ray.
• Cathode rays are a stream of particles
carrying a negative charge.
• The particles carrying a negative charge
are known as electrons.
Cathode Ray TubeCathode Ray Tube

21. Cathode Ray TubeCathode Ray Tube

22. Cathode Ray TubeCathode Ray Tube

23. Cathode Ray Tube inCathode Ray Tube in
ActionAction
Cathode Ray TubeCathode Ray Tube

24. ElectronsElectrons
Electrons – The negative charged
particles that are part of all forms of
matter.

25. Cathode Ray TubeCathode Ray Tube
Thomson received the Nobel Prize in 1906 forThomson received the Nobel Prize in 1906 for
identifying the first subatomic particle—theidentifying the first subatomic particle—the
electron. Research with the Cathode Ray Tubeelectron. Research with the Cathode Ray Tube
determined the following:determined the following:
1.1. Cathode rays were a stream of charged particlesCathode rays were a stream of charged particles
2.2. The particles carried a negative charge.The particles carried a negative charge.
3.3. Changing the metal that made up the electrodesChanging the metal that made up the electrodes
did not change the ray, therefore all types ofdid not change the ray, therefore all types of
matter had these particles.matter had these particles.

26. In the early 1910s, Robert Millikan used the
oil-drop apparatus shown below to
determine the charge of an electron.
MilikanMilikan’s Oil Drop’s Oil Drop
ExperimentExperiment

27. • Charges change in discrete amounts—
1.602 x 10–19
coulombs, the charge of
one electron (now equated to a single
unit, 1–).
• With the electron’s charge and charge-to-
mass ratio known, Millikan calculated the
mass of a single electron.
the mass of
a hydrogen
atom
The ElectronThe Electron

28. • J.J. Thomson's
plum pudding
model of the atom
states that the
atom is a uniform,
positively changed
sphere containing
electrons.
Early Atomic ModelsEarly Atomic Models

29. In 1911, Ernest Rutherford studied how
positively charged alpha particles
interacted with solid matter.
• By aiming the particles
at a thin sheet of gold
foil, Rutherford
expected the paths of
the alpha particles to
be only slightly altered
by a collision with an
electron.
The NucleusThe Nucleus

30. • Although most of the alpha particles went
through the gold foil, a few of them
bounced back, some at large angles.
The NucleusThe Nucleus

31. • The repulsive force between the positively
charged nucleus and positive alpha
particles caused the deflections.
The NucleusThe Nucleus

32. The NucleusThe Nucleus

33. • Rutherford concluded that atoms are
mostly empty space.
• Almost all of the atom's positive charge
and almost all of its mass is contained in
a dense region in the center of the atom
called the nucleus.
• Electrons are held within the atom by
their attraction to the positively charged
nucleus.
The NucleusThe Nucleus

34. Niels Bohr ModelNiels Bohr Model

35. • Rutherford refined the model to
include positively charged particles in
the nucleus called protons.
• James Chadwick received the Nobel
Prize in 1935 for discovering the
existence of neutrons, neutral particles in
the nucleus which accounts for the
remainder of an atom’s mass.
The NucleusThe Nucleus

36. • All atoms are made of three
fundamental subatomic
particles: the electron, the
proton, and the neutron.
• Atoms are spherically
shaped.
The NucleusThe Nucleus

37. • Chemical behavior can be explained by
considering only an atom's electrons.
The NucleusThe Nucleus
• Atoms are mostly empty space, and
electrons travel around the nucleus held
by an attraction to the positively charged
nucleus.

38. • Scientists have determined that protons
and neutrons are composed of subatomic
particles called quarks.
The NucleusThe Nucleus

39. Question?Question?
Atoms are mostly ____.
A. positive
B. negative
C. solid spheres
D. empty space

40. What are the two fundamental
subatomic particles found in the
nucleus?
A. proton and electron
B. proton and neutron
C. neutron and electron
D. neutron and positron
Question?Question?

41. 3:3 How Atoms Differ3:3 How Atoms Differ
Objectives:Objectives:
• Explain the role of atomic number in
determining the identity of an atom.
• Define an isotope.
• Explain why atomic masses are not whole
numbers.
• Calculate the number of electrons, protons,
and neutrons in an atom given its mass
number and atomic number.

42. Atomic NumberAtomic Number
• Moseley (1887-1915) discovered each
element contains a unique positive charge
in their nucleus.
• The number of protons in the nucleus of an
atom identifies the element and is known as
the element’s atomic number.

43. Isotopes and MassIsotopes and Mass
NumberNumber
• All atoms of a particular element have the
same number of protons and electrons but
the number of neutrons in the nucleus can
differ.
• Atoms with the same number of protons but
different numbers of neutrons are called
isotopes.

44. Isotopes and MassIsotopes and Mass
NumberNumber
• The relative abundance of each isotope is
usually constant.
• Isotopes containing more neutrons have a
greater mass.
• Isotopes have the same chemical behavior.
• The mass number is the sum of the protons
and neutrons in the nucleus.

45. Example IsotopeExample Isotope
NotationsNotations
carbon – 13
13
C
C-13

46. Isotopes and MassIsotopes and Mass
NumberNumber

47. Mass of AtomsMass of Atoms
One atomic mass unit (amu) is defined as
1/12th
the mass of a carbon-12 atom.
• One amu is nearly, but not exactly, equal to
one proton and one neutron.

48. Mass of AtomsMass of Atoms
• The atomic mass of an element is the
weighted average mass of the isotopes of
that element.

49. Example ProblemExample Problem
Silver has two isoptopes: 107
47Ag, which has a mass of
106.905 amu and a percent abundance of 52.00%,
and 109
47Ag, which has a mass of 108.905 amu and a
percent abundance of 48.00%. What is the atomic
mass of silver?

50. Example Problem 2Example Problem 2
Chromium’s four naturally occurring isotopes are
provided. Calculate chromium’s atomic mass.
Cr-50 4.35% 49.946amu
Cr-52 83.79% 51.941amu
Cr-53 9.50% 52.941amu
Cr-54 2.36% 53.939amu

51. Question?Question?
An unknown element has 19 protons, 19
electrons, and 3 isotopes with 20, 21 and
22 neutrons. What is the element’s atomic
number?
A. 38
B. 40
C. 19
D. unable to determine

52. Elements with the same number of
protons and differing numbers of
neutrons are known as what?
A. isotopes
B. radioactive
C. abundant
D. ions
Question ?Question ?

53. 3:4 Unstable Nuclei and3:4 Unstable Nuclei and
Radioactive DecayRadioactive Decay
Objective:Objective:
• Explain the relationship between unstable
nuclei and radioactive decay.
• Characterize alpha, beta, and gamma radiation
in terms of mass and charge.

54. RadioactivityRadioactivity
In the late 1890s, scientists noticed some
substances spontaneously emitted radiation, a
process they called radioactivity.
•The rays and particles emitted are called
radiation.
•A reaction that involves a change in an atom's
nucleus is called a nuclear reaction.
• Nuclear reactions can change one
element into another element.

55. Radioactive DecayRadioactive Decay
Unstable nuclei lose energy by emitting
radiation in a spontaneous process called
radioactive decay.
• Unstable radioactive elements undergo
radioactive decay thus forming stable
nonradioactive elements.
• Nuclear stability is determined by the ratio of
neutrons to protons.

56. Radioactive DecayRadioactive Decay
• Atoms that contain too many or too few
neutrons are unstable and lose energy
through radioactive decay to form a stable
nucleus.
• Few exist in nature—most have already
decayed to stable forms.

57. TransmutationTransmutation
Transmutation- When a reaction occurs that
alters an atom’s atomic number.
•Positron – a particle with the same mass as an
electron with the opposite charge.
•Electron Capture - occurs when the nucleus of an
atom draws in a surrounding electron. This
captured electron combines with a proton to form
a neutron.

58. Types of RadiationTypes of Radiation
Alpha radiation is made up of positively
charged particles called alpha particles.
• Each alpha particle contains two protons and
two neutrons and has a 2+
charge.
• Found because they are deflected towards a
negavtively charged plate.
• Written as 4
2 He or α

59. Alpha ParticleAlpha Particle
A nuclear equation showing the radioactive
decay of radium-226 to radon-222.
• The mass is conserved in nuclear equations.

60. Beta ParticleBeta Particle
Beta radiation is radiation that has a
negative charge and emits beta particles.
• Each beta particle is an electron with a 1–
charge.
• Found because they are deflected toward the
positive charged plate
• Written as β or e-

61. Example NuclearExample Nuclear
EquationEquation

62. Beta ParticleBeta Particle

63. Gamma RaysGamma Rays
• Gamma rays are high-energy radiation with no
mass and are neutral.
• Cannot, by themselves, result in the formation
of a new atom.
• Gamma rays account for most of the energy lost
during radioactive decay.
• Written as ϒ
• Example Nuclear Equation:

64. Types of RadiationTypes of Radiation

65. Decay SeriesDecay Series

66. Radiochemical DatingRadiochemical Dating
Carbon undergoes beta decay to form nitrogen.
Carbon-14 has a half-life of 5730 years.
•The amount of stable carbon in the dead
organism remains constant while the carbon-14
continues to decay, the ratio of unstable carbon-
14 to stable carbon-12 and 13 decreases over
time.

67. Half LifeHalf Life
Half-life – is the time required for one-half of a
radioisotope’s nuclei to decay into its products.
N = NN = Noo (1/2)(1/2)nn
N is the remaining amount
No is the initial amount
n is the number of half-lives that have passed. (or this
can be replaced with t/T where t is the elapsed tie and T is
the duration of the half-life with the same units in time).

68. Example ProblemExample Problem
Krypton-85 is used in indicator lights of
appliances. The half-life of krypton-85 is 11years.
How much of a 2.00 mg sample remains after 33
years?

69. Example Problem 2Example Problem 2
Bandages can be sterilized by exposure to gamma
radiation from cobalt-60, which has a half-life of
5.27 years. How much of a 10.0mg sample of
cobalt-60 is left after one half life? Two half lives?
Three half lives?

70. Question ?Question ?
A reaction that changes one element into
another is called what?
A. chemical reaction
B. beta radiation
C. nuclear reaction
D. physical reaction

71. Why are radioactive elements rare in
nature?
A. They do no occur on Earth.
B. Most have already decayed to a
stable form.
C. They take a long time to form.
D. They are too hard to detect.
Question ?Question ?

72. 3:5 Accumulating Content3:5 Accumulating Content
and Skillsand Skills
Objective:
Apply knowledge and skills from previous units
to content learned in this unit.

73. Accumulating ContentAccumulating Content
and Skillsand Skills
How does law of conservation of mass apply
to nuclear reactions?

74. Accumulating ContentAccumulating Content
and Skillsand Skills
How did the scientific method affect the
history of chemistry?

75. Study GuideStudy GuideKey Concepts
• Democritus was the first person to propose
the existence of atoms.
• According to Democritus, atoms are solid,
homogeneous, and indivisible.
• Aristotle did not believe in the existence of
atoms.
• John Dalton’s atomic theory is based on
numerous scientific experiments.

76. Study GuideStudy Guide
Key Concepts
• An atom is the smallest particle of an element
that maintains the properties of that element.
• Electrons have a 1– charge, protons have a 1+
charge, and neutrons have no charge.
• An atom consists mostly of empty space
surrounding the nucleus.

77. Study GuideStudy GuideKey Concepts
• The atomic number of an atom is given by its
number of protons. The mass number of an atom
is the sum of its neutrons and protons.
atomic number = number of protons = number of
electrons
mass number = atomic number + number of neutrons
• Atoms of the same element with different
numbers of neutrons are called isotopes.
• The atomic mass of an element is a weighted
average of the masses of all of its naturally
occurring isotopes.

78. Study GuideStudy Guide
Key Concepts
• Chemical reactions involve changes in the
electrons surrounding an atom. Nuclear
reactions involve changes in the nucleus of
an atom.
• There are three types of radiation: alpha (charge
of 2+), beta (charge of 1–), and gamma (no
charge).
• The neutron-to-proton ratio of an atom’s nucleus
determines its stability.

79. Whose work led to the modern atomic
theory?
A. Dalton
B. Rutherford
C. Einstein
D. Aristotle
Question?Question?

80. Question?Question?
Which particle is not found in the nucleus
of an atom?
A. neutron
B. proton
C. dust
D. electron

81. Question?Question?
Two isotopes of an unknown element
have the same number of:
A. protons
B. neutrons
C. electrons
D. both A and C

82. Question?Question?
Lithium has an atomic mass of 6.941 and
two isotopes, one with 6 neutrons and one
with 7 neutrons. Which isotope is more
abundant?
A. 6
Li
B. 7
Li
C. Both isotopes occur equally.
D. unable to determine

83. Question?Question?
What happens when an element emits
radioactive particles?
A. It gains energy.
B. It gains neutrons.
C. It loses stability.
D. It loses energy.

84. Question?Question?
What is the smallest particle of an element
that still retains the properties of that
element?
A. proton
B. atom
C. electron
D. neutron

85. Question?Question?
How many neutrons, protons, and
electrons does 124
54
Xe have?
A. 124 neutrons, 54 protons, 54 electrons
B. 70 neutrons, 54 protons, 54 electrons
C. 124 neutrons, 70 protons, 54 electrons
D. 70 neutrons, 70 protons, 54 electrons

86. Question?Question?
The primary factor in determining an
atom's stability is its ratio of neutrons
to ____.
A. protons
B. electrons
C. alpha particles
D. isotopes

87. Question?Question?
What is the densest region of an atom?
A. electron cloud
B. nucleus
C. isotopes
D. atomic mass

88. Question?Question?
Why are electrons attracted to the cathode
in a cathode ray tube?
A. The cathode is more stable.
B. The cathode has a positive charge.
C. The cathode has a negative charge.
D. The cathode has no charge.

89. The EndThe End

90. IB 4IB 4

91. IB 5IB 5

92. IB 6IB 6

93. IB 7IB 7

94. IB 8IB 8

95. IB 9IB 9

96. IB 10IB 10

97. IB 11IB 11

98. IB 12IB 12

99. IB 13IB 13

100. IB 14IB 14

101. IB 15IB 15

102. IB 16IB 16

103. IB 17IB 17

104. CIMCIM
3 Properties of Subatomic Particles
12 Rutherford's Experiment
14 Features of an Atom
21 Types of Radiation

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