Nuclear Chem Notes - Teacher

Nuclear Chemistry
A. Radioactivity - the process by which uranium gives off invisible rays.
(Marie Curie, Pierre Curie, and Henri Barquerel - Nobel Prize in Physics 1903)
1. Radiation - the penetrating rays emitted by a radioactive source.
2. Radioisotopes - radioactive isotopes that have an unstable nucleus.
a. Remember: isotopes are atoms of the same element with different numbers of neutrons.
Proton number never changes.
b. Stability of nucleus depends on the ratio of neutrons to protons. Too many neutrons is
unstable.
3. Radioactive decay - process in which unstable nucleus loses energy by emitting radiation.
a. Unstable radioisotopes of one element are turned into stable isotopes of a different
element.
(now proton number changes)
b. Spontaneous.
c. Does not require any input of energy.
B. Types of Radiation
1. Alpha radiation - Greek letter α Consists of helium nuclei that have been emitted from a
radioactive source.
a. Alpha particles - contain two protons and two neutrons and have a double positive
charge. Symbol = 4 2He
b. Example: radioisotope uranium-238
c. When an atom loses of an alpha particle
1. the atomic number (proton number) is lowered by 2.
2. the mass number is lowered by 4. (p + n)
d. Alpha particles are large.
1. They are slow.
2. They are easily stopped (paper or skin)
3. Dangerous if ingested, penetrates soft internal body tissues.
2. Beta radiation - Greek letter β Consists of fast-moving electrons formed by the
decomposition of a neutron in an atom.
The neutron breaks into a proton and an electron.
a. Beta particles - resulting fast moving electrons ejected from nucleus 0 -1e
1. Lighter than alpha particles.
2. More penetrating than alpha particles. Can go through paper & skin.
Stopped by aluminum foil & thin pieces of wood.
3. The new proton stays in the nucleus.
4. Example: radioisotope Carbon-14
3. Gamma radiation - Greek letter γ electromagnetic radiation
a. Emitted by the nuclei of disintegrating radioactive atoms along with alpha or beta
radiation.
b. Example: radioactive Thorium-230
c. Gamma rays have no mass
1. They do not alter atomic number or mass number of atom.
2. Gamma rays are the same as x-rays except in their origin.
a. x-rays are produced from excited electrons in certain metals losing energy, not from

adioactive decay
b. Both gamma and x-rays pass easily through paper, the skin, and wood.
c. They can be stopped, but not completely by several meters of concrete or several
centimeters of lead
C. Nuclear Stability 1500 nuclei are known - 264 are stable- stability depends on the proton to
neutron ratio
up to AN 20 the ratio is 1:1 (p :n) above AN 20 the ratio reaches 1:1.5
1. Band of stability - a neutron verses proton plot of stable nuclei.
a. Nuclei that fall outside the band of stability undergo spontaneous radioactive decay.
b. The type of decay depends on the position of the nucleus with respect to the band of
stability.
2. Beta decay (or beta emission) - To the left of the band of stability, (region A) the nuclei
have too many neutrons. They
turn a neutron into a proton be emitting an electron (beta decay).
3. To the right of the band of stability (region B) the nuclei have too many protons. They
convert a proton to a neutron by
capturing an electron.
a. Positron - a particle with the mass of an electron but a positive charge.
1. A positron may be emitted as a proton is converted to a neutron.
2. When a proton is converted to a neutron
3. the AN (protons) decreases by one
4. the mass (p + n) stays the same
4. At the upper end of the band of stability (region C), the nuclei have too many protons and
too many neutrons
(very heavy).
a. Alpha Emission - they emit alpha particles.
1. The mass number decreases by 4
2. The AN decreases by 2.
b. All nuclei with an AN greater than 83 are radioactive. The majority of these undergo
alpha emission.
D. Half-Life - the time required for one-half of the atoms of a radioisotope to emit radiation and
to decay to products.
1. After one half-life - one-half of the original atoms have decayed into a new element. Onehalf
remain unchanged.
a. After a second half-life only one quarter of the original atoms remain unchanged.100 -->
50 -->25 --> 12 --> etc.
2. Half-lives can be as short as a fraction of a second or as long as several million years.
a. Artificial radioisotopes have very short half-lives. Good for nuclear medicine.
b. It is possible to use this method to date rocks as old as our solar system.
E. Transmutation Reactions
1. Transmutation - the conversion of an atom of one element to an atom of another element.
a. Can be done through radioactive decay.
b. Can also occur if the nucleus is bombarded with high energy protons, neutrons or alpha
particles.
c. Can occur in nature and be done in labs.
2. Transuranium elements - the elements in the periodic table with atomic numbers above

92.
a. None occur in nature.
b. All are radioactive.
F. Nuclear Fission
1. Fission - when the nuclei of certain isotopes are bombarded with neutrons, they split into
smaller fragments.
a. Nucleus breaks into smaller pieces.
b. Neutrons are released, striking other atoms and creating a chain reaction.
c. Unleashes an enormous amount of energy.
d. If uncontrolled the energy release is instantaneous. (Atomic Bombs)
2. Control of Fission - releasing the energy more slowly. Done by nuclear reactors to produce
useful energy.
a. Nuclear Power Plant
- Much of the energy is generated as heat.
- The heat is removed by coolant fluid.
- Steam is generated to drive the turbine.
- A spinning turbine generates electricity.
b. Steps to controlling fission ... prevents the reactor from overheating
a. Neutron moderation - slows down the neutrons so that they can be captured by the
reactor fuel to continue the
chain reaction. (carbon and water)
b. Neutron absorption - decreases the number of slow neutrons to prevent the chain
reaction from going too fast.
(cadmium).
G. Nuclear Fusion
1. Fusion - occurs when two nuclei combine to produce a nucleus of heavier mass.
a. The sun - solar fusion - two hydrogen nuclei fuse to form a single helium nucleus.
b. Releases more energy than fission.
c. Can only occur at an extremely high temperature - greater than 40 million degrees
Celsius. SUN
H. Detecting Radiation - radiation cannot be seen, heard, felt, or smelled.
1. Ionizing Radiation - radiation with enough energy to knock electrons off some atoms of
the bombarded substance to
produce ions. Cannot detect with your five senses. The following monitoring devices are
not protection against radiation.
a. Geiger Counter - gas-filled metal tube to detect radiation.
- used for detecting beta radiation
- gas gets ionized when beta radiation penetrates glass
- gas flows, current flows, electronic counters click
b. Scintillation Counter - device that uses a specially coated phosphor surface to detect
radiation.
- detect all types of radiation
- radiation hits the phosphor surface and produces bright flashes of light, scintillations
- the light is converted to electronic pulses which are measured and recorded
- television screens - scintillations produce picture
c. Film Badge - layers of film covered with black lightproof paper in plastic holder

- film is removed and developed at regular intervals
- strength and type of radiation are determined by the darkening film.
I. Using Radiation
1. Neutron Activation - detects trace (small) amounts of elements in samples
- bombard sample with neutrons causing them to become radioactive
- the half-life and type of radiation emitted is unique for each element
2. Radio-isotope Tracers
a. Reactions - one reactant is labeled, after the reaction takes place, the amount of the tracer
in the product is measured.
- learn about reaction mechanism (many steps)
b. Agriculture Research - tests the effects of herbicides, pesticides, and fertilizers
- tracer connects to substance being tested, plants are treated with the radioactive
substance, measure location and
quantity taken up by the plant - also monitor animals, water, and soil
c. Disease Diagnosis - Iodine-131 detects thyroid problems
- Technetium-99m detects brain tumors and liver disorders
- Phosphorus-32 detects skin cancer
3. Cancer Treatments -
a. Cancer - abnormal cells produced at a faster rate than healthy cells
b. Tumor - runaway growth of cancerous cells in one area.
c. fast-growing cancer cells are damaged more than healthy cells by gamma radiation
d. Gamma radiation will also kill healthy cells to some degree
e. applied with a laser beam, or implanted salt/gold tubes
Nuclear Chemistry
A. Radioactivity - the process by which uranium gives off invisible rays.
(Marie Curie, Pierre Curie, and Henri Barquerel - Nobel Prize in Physics 1903)
1. Radiation - the penetrating rays emitted by a radioactive source.
2. Radioisotopes - radioactive isotopes that have an unstable nucleus.
a. Remember: isotopes are atoms of the same element with different numbers of neutrons.
Proton number never changes.
b. Stability of nucleus depends on the ratio of neutrons to protons. Too many neutrons is
unstable.
3. Radioactive decay - process in which unstable nucleus loses energy by emitting radiation.
a. Unstable radioisotopes of one element are turned into stable isotopes of a different
element.
(now proton number changes)
b. Spontaneous.
c. Does not require any input of energy.
B. Types of Radiation
1. Alpha radiation - Greek letter α Consists of helium nuclei that have been emitted from a
radioactive source.
a. Alpha particles - contain two protons and two neutrons and have a double positive
charge. Symbol = 4 2He
b. Example: radioisotope uranium-238

c. When an atom loses of an alpha particle
1. the atomic number (proton number) is lowered by 2.
2. the mass number is lowered by 4. (p + n)
d. Alpha particles are large.
1. They are slow.
2. They are easily stopped (paper or skin)
3. Dangerous if ingested, penetrates soft internal body tissues.
2. Beta radiation - Greek letter β Consists of fast-moving electrons formed by the
decomposition of a neutron in an atom.
The neutron breaks into a proton and an electron.
a. Beta particles - resulting fast moving electrons ejected from nucleus 0 -1e
1. Lighter than alpha particles.
2. More penetrating than alpha particles. Can go through paper & skin.
Stopped by aluminum foil & thin pieces of wood.
3. The new proton stays in the nucleus.
4. Example: radioisotope Carbon-14
3. Gamma radiation - Greek letter γ electromagnetic radiation
a. Emitted by the nuclei of disintegrating radioactive atoms along with alpha or beta
radiation.
b. Example: radioactive Thorium-230
c. Gamma rays have no mass
1. They do not alter atomic number or mass number of atom.
2. Gamma rays are the same as x-rays except in their origin.
a. x-rays are produced from excited electrons in certain metals losing energy, not from
radioactive decay
b. Both gamma and x-rays pass easily through paper, the skin, and wood.
c. They can be stopped, but not completely by several meters of concrete or several
centimeters of lead
C. Nuclear Stability 1500 nuclei are known - 264 are stable- stability depends on the proton to
neutron ratio
up to AN 20 the ratio is 1:1 (p :n) above AN 20 the ratio reaches 1:1.5
1. Band of stability - a neutron verses proton plot of stable nuclei.
a. Nuclei that fall outside the band of stability undergo spontaneous radioactive decay.
b. The type of decay depends on the position of the nucleus with respect to the band of
stability.
2. Beta decay (or beta emission) - To the left of the band of stability, (region A) the nuclei
have too many neutrons. They
turn a neutron into a proton be emitting an electron (beta decay).
3. To the right of the band of stability (region B) the nuclei have too many protons. They
convert a proton to a neutron by
capturing an electron.
a. Positron - a particle with the mass of an electron but a positive charge.
1. A positron may be emitted as a proton is converted to a neutron.
2. When a proton is converted to a neutron
3. the AN (protons) decreases by one
4. the mass (p + n) stays the same

4. At the upper end of the band of stability (region C), the nuclei have too many protons and
too many neutrons
(very heavy).
a. Alpha Emission - they emit alpha particles.
1. The mass number decreases by 4
2. The AN decreases by 2.
b. All nuclei with an AN greater than 83 are radioactive. The majority of these undergo
alpha emission.
D. Half-Life - the time required for one-half of the atoms of a radioisotope to emit radiation and
to decay to products.
1. After one half-life - one-half of the original atoms have decayed into a new element. Onehalf
remain unchanged.
a. After a second half-life only one quarter of the original atoms remain unchanged.100 -->
50 -->25 --> 12 --> etc.
2. Half-lives can be as short as a fraction of a second or as long as several million years.
a. Artificial radioisotopes have very short half-lives. Good for nuclear medicine.
b. It is possible to use this method to date rocks as old as our solar system.
E. Transmutation Reactions
1. Transmutation - the conversion of an atom of one element to an atom of another element.
a. Can be done through radioactive decay.
b. Can also occur if the nucleus is bombarded with high energy protons, neutrons or alpha
particles.
c. Can occur in nature and be done in labs.
2. Transuranium elements - the elements in the periodic table with atomic numbers above
92.
a. None occur in nature.
b. All are radioactive.
F. Nuclear Fission
1. Fission - when the nuclei of certain isotopes are bombarded with neutrons, they split into
smaller fragments.
a. Nucleus breaks into smaller pieces.
b. Neutrons are released, striking other atoms and creating a chain reaction.
c. Unleashes an enormous amount of energy.
d. If uncontrolled the energy release is instantaneous. (Atomic Bombs)
2. Control of Fission - releasing the energy more slowly. Done by nuclear reactors to produce
useful energy.
a. Nuclear Power Plant
- Much of the energy is generated as heat.
- The heat is removed by coolant fluid.
- Steam is generated to drive the turbine.
- A spinning turbine generates electricity.
b. Steps to controlling fission ... prevents the reactor from overheating
a. Neutron moderation - slows down the neutrons so that they can be captured by the
reactor fuel to continue the
chain reaction. (carbon and water)
b. Neutron absorption - decreases the number of slow neutrons to prevent the chain

eaction from going too fast.
(cadmium).
G. Nuclear Fusion
1. Fusion - occurs when two nuclei combine to produce a nucleus of heavier mass.
a. The sun - solar fusion - two hydrogen nuclei fuse to form a single helium nucleus.
b. Releases more energy than fission.
c. Can only occur at an extremely high temperature - greater than 40 million degrees
Celsius. SUN
H. Detecting Radiation - radiation cannot be seen, heard, felt, or smelled.
1. Ionizing Radiation - radiation with enough energy to knock electrons off some atoms of
the bombarded substance to
produce ions. Cannot detect with your five senses. The following monitoring devices are
not protection against radiation.
a. Geiger Counter - gas-filled metal tube to detect radiation.
- used for detecting beta radiation
- gas gets ionized when beta radiation penetrates glass
- gas flows, current flows, electronic counters click
b. Scintillation Counter - device that uses a specially coated phosphor surface to detect
radiation.
- detect all types of radiation
- radiation hits the phosphor surface and produces bright flashes of light, scintillations
- the light is converted to electronic pulses which are measured and recorded
- television screens - scintillations produce picture
c. Film Badge - layers of film covered with black lightproof paper in plastic holder
- film is removed and developed at regular intervals
- strength and type of radiation are determined by the darkening film.
I. Using Radiation
1. Neutron Activation - detects trace (small) amounts of elements in samples
- bombard sample with neutrons causing them to become radioactive
- the half-life and type of radiation emitted is unique for each element
2. Radio-isotope Tracers
a. Reactions - one reactant is labeled, after the reaction takes place, the amount of the tracer
in the product is measured.
- learn about reaction mechanism (many steps)
b. Agriculture Research - tests the effects of herbicides, pesticides, and fertilizers
- tracer connects to substance being tested, plants are treated with the radioactive
substance, measure location and
quantity taken up by the plant - also monitor animals, water, and soil
c. Disease Diagnosis - Iodine-131 detects thyroid problems
- Technetium-99m detects brain tumors and liver disorders
- Phosphorus-32 detects skin cancer
3. Cancer Treatments -
a. Cancer - abnormal cells produced at a faster rate than healthy cells
b. Tumor - runaway growth of cancerous cells in one area.
c. fast-growing cancer cells are damaged more than healthy cells by gamma radiation

d. Gamma radiation will also kill healthy cells to some degree
e. applied with a laser beam, or implanted salt/gold tubes