Download Marie Curie named the process by which materials give off rays of

Nuclear Chemistry
Ionizing radiation was discovered by _________________________ in 1895, by passing
electric current through an evacuated glass tube and producing continuous X-rays. In
1896, _______________________ found that pitchblende (an ore containing uranium
and radium) caused a photographic plate to darken, and demonstrated that this was the
result of beta radiation (electrons) and alpha particles being emitted. Pierre and Marie
Curie, in 1898 isolated radium and polonium from pitchblende and named the process
through which these forms of energy are produced ________________________. A
radioactive atom, or radioisotope, undergoes drastic changes as it emits this energy,
called _____________________; due to the instability of their nuclei. The stability of
the nucleus depends on the relative proportion of neutrons to protons as well as the
overall size of the nucleus. There are two components to nuclear stability;
_________________________ stability , which refers to the potential energy of a nucleus
relative to the potential energies of its protons and neutrons, and ____________________
stability , which is based on the probability that the nucleus will undergo radioactive
decay.
____________________________ is the process by which an unstable nucleus emits
radiation in order to lose energy. Ernst Rutherford showed that this process is
spontaneous, not requiring the input of energy and eventually results in a stable isotope of
a different element from the original radioisotope – this is known as transmutation. These
transformations can be produced by bombarding atoms with accelerated protons in
particle accelerators, like cyclotrons or the new _____________ collider located near
Geneva. After the discovery of the neutron by _________________, Enrico Fermi
discovered that nuclear transformations of a greater variety can be achieved by using
accelerated _____________________, This ability to break down the nuclei and
produce different atoms disproves Dalton’s theory of indivisible atoms.
Three types of radiation can be emitted during radioactive decay:
1) ___________________, which consists of helium nuclei, also known as
________________________ and contain two protons and two neutrons and
carry a double positive charge
2) ____________________, which consists of fast moving electrons formed by
decomposing a neutron in the atom. The neutron decomposes into a ________,
which remains in the nucleus and a ____________________, the electron, which
is released. This particle carries a negative charge (indicated by the subscript –1
and a superscript 0 indicating a virtual lack of mass) 0-1 e
3) _____________________, which is high energy electromagnetic radiation, often
emitted along with alpha or beta radiation by the nuclei of disintegrating
radioactive isotopes. Since gamma rays have no mass or charge, their emission
does not alter the atomic number or mass number of the atom.
All of the elements with atomic number larger than _____, as well as technetium and
promethium have no stable isotopes, are radioactive and thus undergo decay. Most of
them emit alpha particles, decreasing the mass number by ____ and the atomic number
by _____. In this emission, a small amount of energy associated with radiation is
produced while a small quantity of mass is lost.
Nuclear Chemistry
Every radioisotope has a characteristic rate of decay measured by the time required for
one-half of the nuclei of a sample to decay to stable products. This rate is known as the
_______________ and is used to predict amounts in the exponential decay formula
A = A0 x (1/2)t/T, in which A= amount remaining; A0 = the initial amount; t = time and T
= the half life
There are low levels of radioactive materials present throughout the earth. Elements with
an atomic number higher than 92 are known as the ____________________ elements
and are radioactive to some degree. As more studies were done, it was found that
radiation can cause health issues in two ways. Changes to the body cells, known as
__________________ damage as well as genetic changes, those that involve changes to
cellular ____________ can result from overexposure to radiation. A variety of detection
devices have been used to gauge the amount of radiation exposure. The first such
detector developed is known as a _________________________ counter and is a
cylinder containing a low-pressure gas that when ionized, completes the circuit between
two electrodes. Today, it is important to measure human exposure which generally
involves film badges worn by those who work with radioactive materials and are checked
periodically in a _______________________ counter to determine the dosage the
individual has received.
Common uses of radiation include the approximation of the age of a material using the
isotope _____________________; the use of ___________________________ such as
iodine -123, in medical diagnostics; irradiation of pests in agriculture and sterilization of
food and other consumer products by irradiation. In an example of how branches of
science often work together, _____________________________; the process of dating
the age of wood by counting the tree-rings has been used to verify the half-life of
radioactive carbon and to calibrate the system of carbon dating.
When the nuclei of some isotopes are bombarded with neutrons, they undergo ________,
the splitting of a nucleus into smaller fragments. This process can unleash large amounts
of energy and with the release of additional neutrons as the nucleus fractures, can start a
chain reaction. In a controlled chain reaction, the energy can be harnessed and used to
produce electricity, like in a nuclear ___________. The reaction is sustained using a
neutron ________________, which surrounds the uranium cylinders to slow down the
neutrons, allowing them to be more efficiently captured by the uranium fuel rods. The
loss control of nuclear chain reactions, such as what happened at the ____________
nuclear plant , Pennsylvania and the _________________ reactor in Russia have made
the widespread use of nuclear power an uphill battle in the United States. Contrary to
popular belief, the danger from these accidents is not of a nuclear explosion, but just from
radioactive materials being released into the atmosphere due to a build-up of heat that
cannot be dissipated by the reactor coolant system.
The most vivid example of an uncontrolled nuclear chain reaction is a nuclear bomb, like
the one developed in the 1940s by joint research known as the _____________________
Project. Because of the widespread fear of exposure to nuclear radiation, studies have
Nuclear Chemistry
been done to determine the dangers of the various types of radiation. Alpha radiation is
the least dangerous, with alpha particles stopped by something as lightweight as
___________________. __________ radiation requires the use of something like metal
foil to block the their transmission, while ________________, the highest energy
radiation is blocked (incompletely) only by something as dense as concrete or lead. All
nuclear activity in the USA is governed by the NRC or ________________
________________ ________________.
Another type of nuclear reaction results when nuclei combine to produce a new nucleus
of greater mass. This reaction also requires two beta particles and is known as nuclear
_____________. This is the type of reaction that occurs in the sun. In solar fusion,
hydrogen nuclei fuse to make helium nuclei. The drawback to using fusion as an
affordable source of energy production is that it only takes place at extremely high
_______________________.
Before attempting to balance and work the nuclear decay
problems, complete the nuclear decay gizmo.
Nuclear Chemistry
Name: ___________________________________ Date: _______________________
Student Exploration: Nuclear Decay
Vocabulary: alpha particle, atomic number, beta particle, daughter product, gamma ray,
isotope, mass number, nuclear decay, positron, radioactive, subatomic particle
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
The chart below gives the locations, charges, and approximate masses of three
subatomic particles. The approximate mass of each particle is given in universal mass
units (u).
Particle
Location
Charge
+
Approximate mass
Proton
Nucleus
1
1u
Neutron
Nucleus
0
1u
Electron
Orbitals
1–
0u
1. The mass number of an atom is equal to the sum of protons and neutrons in the
nucleus.
A helium atom has 2 protons and 2 neutrons. What is the mass number of this atom?
_____
2. The atomic number of an element is equal to the number of protons in each atom of
the element. All helium atoms have 2 protons. What is the atomic number of helium?
_____
Gizmo Warm-up
While most atoms are stable, some are
radioactive, which means that they have a
tendency to undergo spontaneous nuclear decay.
The decay of radioactive atoms generally results in
the emission of particles and/or energy.
Several types of nuclear decay can be explored
with the Nuclear Decay Gizmo™. On the Gizmo,
check that Alpha decay and Uranium are
selected.
Nuclear Chemistry
1. Click Play (
) and then click Pause (
) when the alpha particle is clearly
visible. What is an alpha particle made of?
_____________________________________________
2. Click Play and observe. Besides the alpha particle, what else is emitted from the
nucleus during alpha decay?
________________________________________________________
Gamma rays are energetic electromagnetic waves; they are often emitted in nuclear
decay.
Get the Gizmo ready:
Activity A:
Alpha decay
 Click Reset (
).
 Check that Alpha decay and Uranium are
selected.
Question: How does alpha decay change the nucleus of a radioactive atom?
1. Predict: As you observed in the warm-up activity, an alpha particle consists of two
protons and two neutrons. How will the emission of an alpha particle affect the
following?
A. The atomic number of the atom:
_________________________________________
B. The mass number of the atom:
__________________________________________
2. Calculate: Turn on Write equation. What you see is an equation that shows the
original uranium atom on the left. The boxes on the right represent the daughter
product—the atom produced by radioactive decay—and the emitted alpha particle.
A. In the top left box, write the mass number of the daughter product and press
“Enter” on your keyboard. What is this number? ______________
B. In the bottom left box, write the atomic number of the daughter product and
press “Enter.” What is this number? ______________
C. In the next set of boxes, enter the mass number and atomic number of the
alpha particle, which has the same composition as the nucleus of a helium
(He) atom. After filling in the boxes in the Gizmo, write the completed
equation below:
Nuclear Chemistry
D. According to your equation, what isotope remains after the alpha decay of
uranium-238? (Note: You can look up element symbols on the periodic table.)
_____________________________________________________________
______
3. Check: Turn on Show equation, and click Play. The equation will appear at the end
of the animation. Was your prediction correct? _____________ If not, modify your
equation above.
4. Practice: Click Reset, turn off Show equation, and select Polonium. Write an
equation for the alpha decay of polonium, and then use the Gizmo to check your
answer.
What isotope remains after the alpha decay of polonium-212?
_______________________
5. Practice: Click Reset, turn off Show equation, and select Radium. Write an
equation for the alpha decay of radium, and then use the Gizmo to check your
answer.
What dangerous gas is produced by the decay of radium-226?
_______________________
6. Practice: Americium-241 is a radioactive isotope used in smoke detectors. Write an
equation for the alpha decay of Americium-241 below.
Nuclear Chemistry
7. Analyze: In each equation, how is the mass number on the left side of the arrow
related to the sum of mass numbers on the right side of the arrow? Is this true for
atomic numbers?
___________________________________________________________________
______
___________________________________________________________________
______
8. Summarize: In general, how can you determine the mass number of the daughter
product after alpha decay has taken place? How can you determine the atomic
number?
___________________________________________________________________
______
___________________________________________________________________
______
9. Think and discuss: Helium is the second most abundant element in the universe, but
it is rare in Earth’s atmosphere. Most of the helium used to fill balloons and blimps
must be extracted from Earth’s crust. How do you think this helium formed?
___________________________________________________________________
______
___________________________________________________________________
______
Nuclear Chemistry
Get the Gizmo ready:
Activity B:
 Click Reset, and turn off Show equation.
 Select Beta decay from the Type of decay menu.
 Check that Carbon is selected.
Beta decay
Question: How does beta decay change the nucleus of a radioactive atom?
1. Observe: Click Play and watch the animation.
A. What happens to the decaying neutron during beta decay?
____________________
_____________________________________________________________
______
B. What is emitted from the nucleus during beta decay?
_________________________
C. What is the mass number and charge of the emitted particle?
Mass number: _______
Charge: _______
2. Predict: During beta decay, a neutron is transformed into a proton and an electron
(the beta particle), which is emitted. Gamma rays are often emitted during beta
decay as well.
How will beta decay affect the atomic number and mass number of the atom?
___________________________________________________________________
______
3. Calculate: Turn on Write equation. Fill in the first set of boxes with the mass number
and atomic number of the daughter product and the next set of boxes with the mass
number and atomic number of the beta particle. (Note: The atomic number of an
electron is -1.)
Nuclear Chemistry
Check your answer by turning on Show equation and clicking Play. Modify your
equation if necessary. What isotope is produced by the beta decay of carbon-14?
_________________
4. Practice: Turn off Show equation. Fill in the equations for the beta decay of iodine131 and sodium-24 in the spaces below. Use the Gizmo to check your answers.
Get the Gizmo ready:
Activity C:
 Click Reset, and turn off Show equation.
 Select Positron emission.
 Check that Carbon is selected.
Protons into
neutrons
Introduction: A positron is a type of antimatter that is equivalent to an electron. If a
positron and an electron meet, they will annihilate one another in a burst of gamma rays.
Question: How do positron emission and electron capture change an atom?
1. Observe: Click Play and watch the animation.
A. What happens to the decaying proton during positron emission?
________________
_____________________________________________________________
______
B. What is the mass number and charge of the emitted positron?
__________________
Mass number: _______
Charge: _______
2. Predict: During positron emission, a proton is transformed into a neutron and a
positron, which is emitted. The positron will fly through space until it encounters an
electron. How will positron emission affect the atomic number and mass number of
the atom?
___________________________________________________________________
______
Nuclear Chemistry
3. Calculate: Turn on Write equation. Fill in the first set of boxes with the mass number
and atomic number of the daughter product and the next set of boxes with the mass
number and atomic number of the positron. (Note: The atomic number of a positron
is 1.)
Check your answer by turning on Show equation and clicking Play. Modify your
equation if necessary. What isotope is produced when carbon-11 emits a positron?
_______________
4. Practice: Turn off Show equation. Fill in the equations for the positron emission of
xenon-118 and manganese-50 in the spaces below. Use the Gizmo to check your
answers.
5. Observe: Click Reset. Select Electron capture, and make sure Tungsten is
selected. Click Play and watch the animation.
A. What happened to the proton after absorbing an electron?
____________________
_____________________________________________________________
______
B. What is the mass number and charge of the absorbed electron?
Mass number: _______
Charge: _______
6. Predict: During electron capture, an electron is absorbed into the nucleus, causing a
proton to transform into a neutron. How will electron capture affect the atomic
number and mass number of the atom?
___________________________________________________________________
______
Nuclear Chemistry
7. Calculate: Note that in this equation the particle is absorbed, rather than emitted. Fill
in the first set of boxes with the mass number and atomic number of the absorbed
electron. Fill in the last set of boxes with the mass number and atomic number of the
daughter product.
Turn on Show equation and click Play to check. Modify your equation if necessary.
What isotope is produced when tungsten-179 absorbs an electron?
___________________
8. Practice: Turn off Show equation. Fill in the electron capture equations for gold-195
and neodymium-141 in the spaces below. Use the Gizmo to check your answers.
9. Think and discuss: What do electron capture and positron emission have in
common?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Nuclear Chemistry
1. A radioisotope of the element lead (Pb) decays to an isotope of the element
bismuth (Bi) by emission of a beta particle. Complete the equation for the decay
process by supplying the missing atomic number and mass number.
210
PB  83Bi + 0-1e
2. Write the symbol and charge for each:
alpha particle
beta particle
gamma ray
3. Balance the following nuclear equations:
a. 23892U  23490Th +
b.
234 Th
90
c.
234
91Pa
d.

234
91Pa

+
0
U +
-1e
U 
230 Th
90
+ 42He

226
88Ra
+ He
Ra 
222
86Rn
+
e.
230 Th
90
f.
226
g.
222
86 Rn
h.
4
2He
 84Po
+ 42He
84Po

+
i.
214
82Pb

j.
218
84Po

214
82Pb
83Bi
218
+
At +
0
4
2He
-1e
0
-1e
4. The disintegration of radium-226 produces an isotope of radon and alpha
radiation. The atomic number of radium (Ra) is 88 and the atomic number of
radon(Rn) is 86. Write a balanced equation for this transformation.
5. The following radioisotopes are beta emitters. Write balanced nuclear equations
for their decay processes.
a. Carbon – 14
b. Strontium – 90
c. Potassium – 40
Nuclear Chemistry
d.
206
81Ti
6. The following radioactive nuclei decay by emitting alpha particles. Write the
product of the decay process for each.
a.
238
94 Pu
b.
210
83
Bi
c.
210
84
Po
7. A patient is administered 20 mg of iodine – 131. How much of this isotope will
remain in the body after 40 days if the half-life for iodine – 131 is 8 days?
8. A radioactive isotope has a half-life of 0.75 hr. Starting with 3.2 x 1021 atoms,
how many atoms will be left at the end of 4.5 hours.
9. The NRC regulates the disposal of radioactive chemicals. Radioactive samples of
less than 20g can be disposed of in normal hazardous waste facilities. If the half –
life of Bohrium is 1.5 hours, how long will it take for 92.6g of radioactive
Bohrium to decay sufficiently that the remaining sample can be discarded?
10. How are the mass number and atomic number of a nucleus affected by the loss of
the following?
a. Beta particle
b. Alpha particle
c. Gamma ray