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Tuesday, September 25th
Today:
•Review
•Quiz
•Nuclear Chemistry, Chapter 4
•Group Assignment
•Test Review
Frequency : CD
Review Chapter 3
Isotopes
Isotopes
 are atoms of the same element that have different mass
numbers.
 have the same number of protons but different numbers
of neutrons.
 can be distinguished by atomic symbols.
Energy Levels and Sublevels
Sublevels and Orbitals
Each sublevel consists of a specific number of
orbitals.
 An s sublevel contains one s orbital.
 A p sublevel contains three p orbitals.
 A d sublevel contains five d orbitals.
 An f sublevel contains seven f orbitals.
Electron Configuration
An electron configuration
 lists the filled and partially filled energy levels in order of
increasing energy.
 lists the sublevels filling with electrons in order of increasing
energy.
 uses superscripts to show the number of electrons in each
sublevel.
 for neon is as follows: number of electrons = 10
1s22s22p6
Abbreviated Configurations
In an abbreviated configuration,
 the symbol of the noble gas is in brackets, representing
completed sublevels.
 the remaining electrons are listed in order of their sublevels.
Example: Chlorine has the following configuration:
1s22s22p63s23p5
[Ne]
The abbreviated configuration for chlorine is
[Ne]3s23p5.
Valence Electrons
The valence electrons
 determine the chemical properties of the elements.
 are the electrons in the outermost, highest energy level.
 are related to the group number of the element.
Example: Phosphorus has 5 valence electrons.
5 valence
electrons
P Group 5A(15)
1s22s22p63s23p3
Writing Electron-Dot Symbols
The electron-dot symbols for
 Groups 1A (1) to 4A (14) use single dots:
Na
Mg
Al
C
 Groups 5A (15) to 7A (17) use pairs and single dots:
P
O
Cl
Atomic Radius
Ionization Energy
Ionization energy
 is the energy it takes to remove a valence electron from an
atom in the gaseous state.
Na(g) + Energy (ionization)
Na+(g) + e–
 decreases down a group, increasing across the periodic table
from left to right.
Clickers!
Frequency: CD
How many orbitals are in the d
sublevel?
a) 1
c) 5
b) 3
d) 7
Which of the following is an alkaline
earth metal?
a) sodium
c) magnesium
© 2013 Pearson Education,
Inc.
b) aluminum
d) silicon
There are four isotopes of sulfur: 32S,
33S, 34S, and 35S. Based upon the
atomic mass listed in the periodic
table, 32.07, which isotope is the most
abundant?
a) 32S
c) 34S
© 2013 Pearson Education,
Inc.
b) 33S
d) 35S
The electron configuration for
chlorine, Cl, is ________.
a) 1s22s22p63s23p5
b) 1s22s22p63s23p64s1
c) 1s22s22p63s23p6
d) 1s22s22p63s13p5
© 2013 Pearson Education,
Inc.
What is the correct Electron Dot
Symbol for Carbon?
a) C
b) C
c) C
d) C
Which is the largest element?
a) Te
c) P
b) O
d) As
Which element has the smallest
ionization energy?
a) Li
c) Ca
b) Na
d) B
Quiz 4
Chapter 4 - Nuclear Chemistry
Radioactive Isotopes
A radioactive isotope
 has an unstable nucleus and usually has an atomic
number above 20.
 emits radiation to become more stable.
 can be one or more of the isotopes of an element.
 is identified by writing the mass number after the
element symbol, such as iodine-131 or I-131.
 has the following symbol:
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
22
Some Stable and Radioactive Isotopes
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
23
Types of Radiation
Radiation is the energy emitted by an unstable atom in
the process of becoming more stable. It takes the form of
 alpha particles, which are identical to a helium nucleus,
 beta particles, which are high-energy electrons with a
charge of 1− and a mass number of 0,
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
24
Types of Radiation (continued)
 positron, similar to a beta particle with a charge of 1+
and mass number of 0, and
 gamma rays, which are high-energy radiation often
emitted with other types of radiation. They are written
with a mass and atomic number of 0.
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
25
Summary, Types of Radiation
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
26
Biological Effects of Radiation
 When radiation strikes molecules, electrons may be
knocked away, forming unstable ions.
 If this ionizing radiation passes through the human body,
it may interact with water molecules, removing an
electron, producing H2O+.
 H2O+ can cause undesirable chemical reactions damaging
cells.
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
27
Radiation Protection
Radiation protection requires
 paper and clothing for alpha particles,
 a lab coat or gloves for beta particles,
 a lead shield or a thick concrete wall
for gamma rays,
 limiting the amount of time spent near
a radioactive source, or
 increasing the distance from the
source.
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
28
Alpha Decay
When a radioactive nucleus
emits an alpha particle, a
new nucleus forms that has
 a mass number 4 less
than that of the initial
nucleus, and
 an atomic number that
has decreased by 2 from
that of the initial nucleus.
Completing Nuclear Equations
In a completed nuclear equation,
 the sum of the mass numbers of the unstable
isotope and the products are equal, and
 the sum of the atomic numbers of the
unstable isotope and the products are equal.
Sum of Mass Numbers
Sum of Atomic Numbers
Guide to Completing a Nuclear
Equation
Equation for Alpha Decay
Write an equation for the alpha decay of 222Rn.
Step 1 Write the incomplete equation.
222
86
Rn  ? +
4
2
He
Step 2 Determine the missing mass number.
Step 3 Determine the missing atomic number.
Step 4 Determine the symbol of the new nucleus.
Equation for Alpha Decay
Write an equation for the alpha decay of 222Rn.
Step 5 Complete the nuclear equation.
Beta Decay
A beta particle
 is an electron
emitted from the
nucleus.
 forms when a
neutron in the
nucleus breaks
down into a proton
and an electron.
Equation for a Beta Emitter
Step 1 Write the incomplete equation.
42K (potassium-42), a beta emitter.
Step 2 Determine the missing mass number.
Step 3 Determine the missing atomic
number.
Step 4 Determine the symbol of the new
Equation for a Beta Emitter
Step 5 Complete the nuclear equation.
Learning Check
Write the nuclear equation for the beta decay of
Co-60.
Solution
Write the nuclear equation for the beta decay of
Co-60.
Step 1 Write the incomplete equation.
Step 2 Determine the missing mass number.
Step 3 Determine the missing atomic number.
Step 4 Determine the symbol of the new nucleus.
Solution
Write the nuclear equation for the beta
decay of
Co-60.
Step 5 Complete the nuclear equation.
beta particle
Positron Emission
In positron emission,
 a proton is converted to a neutron and a
positron.
 the mass number of the new nucleus is the
same, but the atomic number decreases by
1.
Gamma Radiation
In gamma radiation,
 energy is emitted from an unstable nucleus,
indicated by m following the mass number
technetium-99m, and
 the mass number and the atomic number
of the new nucleus are for the same
element.
Summary of Types of Radiation
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
42
Clicker Review
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
43
1.
An alpha particle is the same as a_____.
a)
b)
c)
d)
helium-5 nucleus
helium-4 nucleus
helium-3 nucleus
proton
2. The nuclear reaction
is an example of______.
a)
b)
c)
d)
gamma radiation
positron emission
beta decay
alpha decay
3.
Uranium-238 decays by emission of an alpha
particle. The product of this decay is_____.
a)
b)
c)
d)
4.
222R decays to 218P through what process?
a)
b)
c)
d)
Beta decay
Alpha decay
Positron emission
Gamma emission
Producing Radioactive Isotopes
Radioactive isotopes are produced
 when a stable nucleus is converted to a
radioactive nucleus by bombarding it with a
small particle.
 in a process called transmutation.
Producing Radioactive Isotopes
When nonradioactive B-10 is bombarded
by an alpha particle, the products are
radioactive N-13 and a neutron.
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
49
Learning Check
What radioactive isotope is produced when
a neutron bombards 59Co and emits an alpha
particle?
Exposure to Radiation
Exposure to radiation
occurs from
 naturally occurring
radioisotopes,
including potassium40.
 medical and dental
procedures.
 air travel, radon, and
smoking cigarettes.
Radiation Sickness
 Exposure to radiation of less than 25 rem is
usually not detected.
 Whole-body exposure of 1 Sv produces a
temporary decrease in the number of white
blood cells.
 Exposure to radiation greater than 1 Sv may
cause radiation sickness.
Radiation Sickness
 This amount of radiation to the whole body is called
the lethal dose for one-half the population, or the LD50.
 LD50 varies for different life forms.
 For people, whole body radiation of 6 Sv or greater
would be fatal within a few weeks.
Half-life
The half-life of a radioisotope is the time for the
radiation level to decrease (decay) to one-half of
the original value.
Decay Curve
A decay curve shows the decay of radioactive
atoms and the remaining radioactive sample.
Half-life Calculations
 In one half-life, 40 mg of a radioisotope
decays to 20 mg.
 After two half-lives, 10 mg of a radioisotope
remain.
Initial
40 mg
2 half-lives
1 half-life
20 mg
10 mg
Guide to Calculating Half-lives
Sample Calculation of Half-lives
P-32, a radioisotope used to treat leukemia, has a half-life of
14.3 days. If a sample contains 8.0 mg of P-32, how many
milligrams of P-32 remain after 42.9 days?
Step 1 State the given and needed quantities.
Analyze the Problem.
Given
Need
8.0 mg of P-32
half-life of 14.3 days
42.9 days elapsed
milligrams of P-32
remaining
Sample Calculation of Half-lives
P-32, a radioisotope used to treat leukemia, has a half-life
of 14.3 days. If a sample contains 8.0 mg of P-32, how
many milligrams of P-32 remain after 42.9 days?
Step 2 Write a plan to calculate the unknown
quantity.
days
half-life
milligrams of

32
15
P
number of half-lives
number of
half-lives
milligrams
remaining

32
15
P
Sample Calculation of Half-lives
P-32, a radioisotope used to treat leukemia, has
a half-life of 14.3 days. If a sample contains 8.0
mg of P-32, how many milligrams of P-32 remain
after 42.9 days?
Step 3 Write the half-life equality and
conversion
factors.
Sample Calculation of Half-lives
P-32, a radioisotope used to treat leukemia, has a halflife of 14.3 days. If a sample contains 8.0 mg of P-32,
how many milligrams of P-32 remain after 42.9 days?
Step 4 Set up the problem to calculate the needed
quantity.
Half-Lives of Some Radioisotopes
Radioisotopes that are
 naturally occurring tend to have long half-lives.
 used in nuclear medicine have short half-lives.
Practice
If the half-life of a material is 31.0 days,
how many days does a 100.0g sample
take to be less than 5.0g remaining?
© 2013 Pearson Education, Inc.
Chapter 4, Section 1
63
Nuclear Fission
In nuclear fission,
 a large nucleus is bombarded with a
small particle,
 the nucleus splits into smaller nuclei
and several neutrons, and
 large amounts of energy are released.
Nuclear Fission
When a neutron bombards U-235,
 an unstable nucleus of U-236 forms and
undergoes fission (splits),
 smaller nuclei are produced, such as Kr-91 and
Ba-142, and
 neutrons are released to bombard more 235U.
Nuclear Fission Diagram and
Equation
1
0
n + 23592 U  236
92 U 
© 2013 Pearson Education, Inc.
91
36
1
Kr + 142
Ba
+
3
56
0 n + energy
Chapter 4, Section 1
66
Learning Check
Supply the missing atomic symbol to complete
the equation for the following nuclear fission
reaction.
1
0
n +
235
92
U 
137
52
Te + ? + 210 n + energy
Chain Reaction
A chain reaction
occurs when a critical
mass of uranium
undergoes fission,
releasing a large
amount of heat and
energy that produces
an atomic explosion.
Nuclear Power Plants
In nuclear power plants,
 fission is used to produce energy.
 control rods in the reactor absorb
neutrons to slow and control the chain
reactions of fission.
Nuclear Fusion
Nuclear fusion
 occurs at extremely high temperatures
(100,000,000 C).
 combines small nuclei into larger nuclei.
 releases large amounts of energy.
 occurs continuously in the sun and stars.
Learning Check
Indicate if each of the following describes
nuclear fission or fusion, or both.
A. A nucleus splits.
B. Large amounts of energy are
released.
C. Small nuclei form larger nuclei.
D. Hydrogen nuclei react.
E. Several neutrons are released.
Group Assignment #4
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