differentiating chemical reactions from nuclear reactions 1
TRANSCRIPT
Differentiating Chemical Reactions
from Nuclear Reactions
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CHEMICAL NUCLEAR
Occurs when bonds are broken or formed.
Occurs when nuclei emit particles and/or rays.
Atoms remained unchanged, though may be rearranged.
Atoms often converted into atoms of another element.
Involves valence electrons May involve protons, neutrons or electrons
Small energy changes HUGE energy changes
Reaction rates affected by temp and pressure
Reaction rate NOT normally affected temp and pressure
CHEMICAL NUCLEAR
Occurs when bonds are broken or formed.
Occurs when nuclei emit particles and/or rays.
Atoms remained unchanged, though may be rearranged.
Atoms often converted into atoms of another element.
Involves valence electrons May involve protons, neutrons or electrons
Small energy changes HUGE energy changes
Reaction rates affected by temp and pressure
Reaction rate NOT normally affected temp and pressure
CHEMICAL NUCLEAR
Occurs when bonds are broken or formed.
Occurs when nuclei emit particles and/or rays.
Atoms remained unchanged, though may be rearranged.
Atoms often converted into atoms of another element.
Involves valence electrons May involve protons, neutrons or electrons
Small energy changes HUGE energy changes
Reaction rates affected by temp and pressure
Reaction rate NOT normally affected temp and pressure
CHEMICAL NUCLEAR
Occurs when bonds are broken or formed.
Occurs when nuclei emit particles and/or rays.
Atoms remained unchanged, though may be rearranged.
Atoms often converted into atoms of another element.
Involves valence electrons May involve protons, neutrons or electrons
Small energy changes HUGE energy changes
Reaction rates affected by temp and pressure
Reaction rate NOT normally affected temp and pressure
CHEMICAL NUCLEAR
Occurs when bonds are broken or formed.
Occurs when nuclei emit particles and/or rays.
Atoms remained unchanged, though may be rearranged.
Atoms often converted into atoms of another element.
Involves valence electrons May involve protons, neutrons or electrons
Small energy changes HUGE energy changes
Reaction rates affected by temp and pressure
Reaction rate NOT normally affected temp and pressure
CHEMICAL NUCLEAR
Occurs when bonds are broken or formed.
Occurs when nuclei emit particles and/or rays.
Atoms remained unchanged, though may be rearranged.
Atoms often converted into atoms of another element.
Involves valence electrons May involve protons, neutrons or electrons
Small energy changes HUGE energy changes
Reaction rates affected by temp and pressure
Reaction rate NOT normally affected temp and pressure
Write a multiple-choice test question for the previous chart.
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Nuclear Radiation
Natural Radioactivity
A person working with radioisotopes wears protective clothing and gloves and stands behind a shield.
Radioactivity
Any process where the nucleus emits particles or energy
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Unstable nucleus.
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Radioactive Isotopes
A radioactive isotope • has an unstable nucleus• emits radiation to become more stable• can be one or more isotopes of an element• is written with a mass number and an atomic
number• includes the mass number in its name
Example: iodine-131
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Examples of Radioactive Isotopes
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Learning Check
Thallium-201 is used for heart scans to determine cardiac function.
A. How many protons are in thallium-201?
B. How many neutrons are in thallium-201?
C. What is the atomic symbol of thallium-201?
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Nuclear Radiation
Nuclear radiation • is the radiation emitted by an unstable atom• takes the form of alpha particles, neutrons,
beta particles, positrons, or gamma rays
A representation of a Geiger-Müller counter
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Alpha Particle
An alpha () particle has• a helium nucleus• 2 protons and 2 neutrons• a mass number of 4• a charge of 2+• a low energy compared to
other radiation particles
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Beta ParticleA beta () particle • is a high-energy electron• has a mass number of 0• has a charge of 1-• forms in an unstable nucleus when a neutron
changes into a proton and an electron
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PositronA positron ( +)• has a mass number of 0• has a charge of 1+• forms in an unstable nucleus when a proton
changes into a neutron and a positron
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Gamma () RayA gamma () ray • is high-energy radiation• has a mass number of 0• has a charge of 0• is emitted from an unstable nucleus to give a
more stable, lower energy nucleus
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Summary of Common Forms of Nuclear Radiation
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Learning Check
Give the mass number and charge of each type of
radiation.
1. alpha particle
2. positron
3. beta particle
4. neutron
5. gamma ray
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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 • increasing the distance from the source
Radiation Protection
How Far Away? Inverse Square Law
Write a multiple choice test question over this topic!
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Radiation and Shielding Required
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Radiation Protection
Different types of shielding are needed for different radiation particles.
Radioactive particles/rays vary greatly in penetrating power.
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Learning Check
Indicate the type of radiation (alpha, beta, and/or gamma) protection for each type of shielding.
1) heavy clothing
2) paper
3) lead
4) lab coat
5) thick concrete
A person working with radioisotopes wears protective clothing and gloves and stands behind a shield.
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Nuclear Radiation
Nuclear Equations
A radon gas detector is used to determine radon levels in buildings with inadequate ventilation.
Radioactive Decay
In radioactive decay, • a nucleus spontaneously emits radiation• a nuclear equation is written for the radioactive
nucleus, the new nucleus, and the radiation emitted
Radioactive nucleus
new nucleus + radiation (, , , +)
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In a nuclear equation, the type of radiation emitted causes
• changes in the mass numbers
• changes in the atomic numbers for the nuclei of the unstable and stable nuclei
Nuclear Equations
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In a balanced nuclear equation, • the sum of the atomic numbers for the nuclei
of the reactant and the products must be equal
Mass Numbers Total = 238 = 238
Total = 92 = 92 Atomic Numbers
Balancing Nuclear Equations
238 234 492 90 2U Th + He
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Guide to Completing a Nuclear Equation
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Alpha Decay
In alpha decay, a
radioactive nucleus emits
an alpha particle to form a
new nucleus that has • a mass number 4 less
than that of the initial nucleus
• an atomic number that has decreased by 2 from that of the initial nucleus
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Example of Writing an Equation for Alpha Decay
Write an equation for the alpha decay ofSTEP 1 Write the incomplete nuclear equation.
STEP 2 Determine the missing mass number.
222 = ? + 4
222 – 4 = 218
218 = ? (mass number of new nucleus)
22286 Rn
222 486 2Rn ? + He
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Equation for Alpha Decay (continued)
STEP 3 Determine the missing atomic number. 86 = ? + 2
86 – 2 = ? 84 = ? (atomic number of new nucleus
STEP 4 Determine the symbol of the new nucleus.
Symbol of element 84 = Po
STEP 5 Complete the nuclear equation.
222 218 486 84 2Rn Po + He
21884 Po
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Beta Decay
Beta decay occurs when• an electron (beta
particle) is emitted from the nucleus
• a neutron in the nucleus breaks down
1 0 10 -1 1 + H n e
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Write an equation for the beta decay of potassium-42.STEP 1 Write the incomplete nuclear equation.
STEP 2 Determine the missing mass number. 42 = ? + 0
42 0 = 42 = ? (mass number of new nucleus)
STEP 3 Determine the missing atomic number. 19 = ? 1
19 + 1 = ? 20 = ? (atomic number of new nucleus)
Writing an Equation for a Beta Emitter
42 0 19 -1K ? + e
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STEP 4 Determine the symbol of the new nucleus.
Symbol of element 20 = Ca
STEP 5 Complete the nuclear equation.
Writing an Equation for a Beta Emitter (continued)
42 20Ca
42 42 0 19 20 -1K Ca + e
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Write the nuclear equation for the beta decay of Xe-133.
Learning Check
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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
Positron Emission
1 1 01 0 +1H n e
49 49 0 25 24 +1Mn Cr + e
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Write the nuclear equation for the positron emission by Rb-82.
Learning Check
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In gamma radiation,• energy is emitted from an unstable nucleus,
indicated by m following the mass number• the mass number and the atomic number of the
new nucleus are the same
Gamma ( ) Radiation
99m 99 0 43 43 0Tc Tc +
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Summary of Types of Radiation
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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
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What radioactive isotope is produced when a neutron bombards cobalt-59 and an alpha particle is emitted?
Learning Check
59 1 427 0 2Co + ? + Hen
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Recall From Lab: The decay series.
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Nuclear Radiation
Radiation Measurement
A radiation technician uses a Geiger Counter to check radiation levels.
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Radiation Detection
A Geiger counter • detects beta and gamma radiation• uses ions produced by radiation to create
an electrical current
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Radiation Measurement
Radiation units of activity include• curie (Ci) SI unit = becquerel (Bq)
number of atoms that decay in one second 1 Ci = 3.7 x 1010 disintegrations/s
1 Ci = 3.7 x 1010 Bq• rad (radiation absorbed dose) SI unit = gray(Gy) radiation absorbed by the tissues of the body
1 Gy = 100 rad• rem (radiation equivalent) SI unit = sievert (Sv) biological damage caused by different types of radiation = absorbed dose (rad) x factor 1 Sv = 100 rem
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Units of Radiation Measurement
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Exposure to Radiation
Exposure to radiation occurs from
• naturally occurring radioisotopes
• medical and dental procedures
• air travel, radon, and smoking cigarettes
Radiation Sickness
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Radiation sickness• depends on the dose of radiation received at
one time• is not detected under 25 rem• involves a decrease in white blood cells at
100 rem• includes nausea and fatigue over 100 rem• reduces white-cell count to zero over 300 rem • leads to death in 50% of people at 500 rem
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Nuclear Radiation
Half-Life of a Radioisotope
The age of the Dead Sea scrolls was determined using carbon-14.
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Half-LifeThe half-life of a radioisotope is the time for the radiation level (activity) to decrease (decay) to one-half of its original value.
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Decay Curve
A decay curve shows• the decay of radioactive atoms• the remaining radioactive sample
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Half-lives of Some RadioisotopesHalf-lives of radioisotopes that are• naturally occurring tend to be long• used in nuclear medicine tend to be short
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• In one half-life, 40 mg of a radioisotope decays to 20 mg.
• After two half-lives, 10 mg of radioisotope remain.
40 mg x 1 x 1 = 10 mg 2 2
1 half-life 2 half-lives
Initial40 mg
20 mg10 mg
Half-Life Calculations
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Examples of Half-Lives
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Using Half-lives
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The half-life of iodine-123 is 13 h. How much of a 64-mg sample of I-23 is left after 26 h?
1) 32 mg
2) 16 mg
3) 8 mg
Learning Check
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Nuclear Radiation
Medical Applications Using Radioactivity
Used by >>1 in 3 admitted to hospital
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Medical Applications
Radioisotopes with short half-lives are used in nuclear medicine because they
• have the same chemistry in the body as the nonradioactive atoms
• give off radiation that exposes a photographic plate (scan), giving an image of an organ
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Using a Scanner to Detect Radiation
(a) A scanner is used to detect radiation from a radioisotope that has accumulated in an organ. (b) A scan of the thyroid show the accumulation of radioactive iodine-131 in the thyroid.
Radioactive Tracers
Technetium-996 hr half-lifeAccumulate in cells
with rapid growth (tumors)
Radioactive Tracers:Gadolinium-153
Accumulated in bone Osteoporosis
Radioisotopes in Nuclear Medicine
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Learning Check
Which of the following radioisotopes are most likely to be used in nuclear medicine?
1) K-40 half-life 1.3 x 109 years
2) K-42 half-life 12 hours
3) I-131 half-life 8 days
Write a test question regarding radioactive tracers used in medicine.
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Positron Emission Tomography (PET)
In positron Emission Tomography (PET), • positrons are emitted from positron emitters such
as carbon -11, oxygen-15, and fluorine-18
• positrons are used to study brain function and metabolism
• positrons combine with electrons to produce gamma ray that can be detected, giving a three-dimensional image
18 18 09 8 1F O + e
0 0 01 1 0 + e e
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Positron Emission Tomography (PET)
These PET scans of the brain show a normal brain on the left and a brain affected by Alzheimer’s disease on the right.
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Computed Tomography (CT)
In computed tomography (CT), 30 000 X-rays• are directed at the brain in layers• are absorbed at different rates due to differences
in densities of body tissues and fluids• create three-dimensional images of the brain and
any tumors or hemorrhages
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Computed Tomography (CT)
A CT scan shows a brain tumor (yellow) on the right side of the brain.
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Magnetic Resonance Imaging (MRI)
In magnetic resonance imaging (MRI)• protons in the presence of a strong magnetic field
align with the magnetic field• protons release energy when magnetic field is
removed• protons in different environments emit energies of
different frequencies to provide images of soft tissue
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Magnetic Resonance Imaging (MRI)
An MRI scan provides images of the heart and lungs.
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Nuclear Radiation
Nuclear Fission and Fusion
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In nuclear fission, • a large nucleus is bombarded with a small
particle• the nucleus splits into smaller nuclei and
several neutrons• large amounts of energy are released
Nuclear Fission
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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• neutrons are released to bombard more U-235
nuclei
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Nuclear Fission
1 235 236 91 142 10 92 92 36 56 0 + U U Kr + Ba + 3 + energyn n
E=mc2
Eenergy mmass cspeed of light
(3.0 x 108 m/s)
Small mass=large output
Mass of proton and neutron in the nucleus is less than the same protons and neutrons separate? Mass of proton and neutron in the nucleus is less than the same protons and neutrons separate? Missing mass is the mass defect = to binding energy.Convert mass to energy = equation tells you how much energy
Critical Mass Minimum fissionable
isotopes needed to provide neutrons to sustain chain reaction
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Chain Reaction
A chain reaction occurs • when a critical mass of uranium undergoes
fission• releasing a large amount of heat and
energy that produce an atomic explosion
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Chain Reaction
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Learning Check
Supply the missing atomic symbol to complete theequation for the following nuclear fission reaction.
1 235 137 10 92 52 0 + U Te + ? + 2 + energyn n
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Nuclear Power Plants
In nuclear power plants, • fission is used to produce energy• control rods in the reactor absorb
neutrons to slow the fission process
Nuclear power plants supply about 10% of the electricity in the United States.
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Diagram of a nuclear power plant.
Copyright © by McDougal Littell. All rights reserved.
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Schematic of the reactor core.
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Nuclear Power Plants
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Diagram for the tentative plan for deep underground isolation of nuclear waste.
Fusion
Interior of sun 15 million °C
Nuclei combine H ‘s combine to form He
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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
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Nuclear Fusion
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Indicate if each of the following is
1) nuclear fission or 2) nuclear fusion
___ 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
Classify each as fission or fusion
Learning Check
Concept Map
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Smoke Detectors Alpha emitters
Charged• current with smoke• Am-241