Nuclear Chemistry
types of masses
(SMALLEST) subcritical mass critical mass (LARGEST) supercritical mass
Carbon's Useful Isotopes
- Carbon has known isotopes. - Its 2 stable isotopes are: • carbon-12 (C-12). • carbon-13 (C-13) . - Most unstable isotopes decay quickly. - Carbon-14 decays very slowly. It is used for radiocarbon dating
Isotopes and Stability
- Strong nuclear force can hold the nucleus together when there are "enough" neutrons present to counteract repulsive forces. - Too few neutrons relative to protons can lead to instability. - As the atomic # increases, the neutron-to-proton ratio needed for a stable nucleus increases. Relatively more neutrons are needed as the # of protons increases.
Mass-Energy Equivalence
- The law of conservation of mass states that mass can neither be created nor destroyed. - The law of conservation of energy states that energy can neither be created nor destroyed. - Einstein showed mass and energy equivalence: E = mc2 .
Einstein's Equation
- The laws of conservation of mass and energy needed modification. - Matter can be converted into energy c = The speed of light in a vacuum, about 3.00 × 108 m/s
Radiocarbon Dating
- is used to estimate the age of (living or once living) remains. • It uses the radioisotope C-14. • After death, organisms stop their intake of C-14. • C-14's half-life is 5,730 years. • It is useful for dating objects up to about 70,000 years old.
which forces are acting on the nucleus?
- strong nuclear force - electrostatic forces of repulsion
Which applies to fusion?
- takes place in the Sun - plays a role in the production of essentially all elements heavier than helium - releases large amounts of energy
radiation effects depend on:
- the type of radiation (energy) - the pathway of exposure (ability to permeate). All forms of radiation can cause cancer and other health problems.
Cold Fusion
- theory of cold fusion states that fusion reactions that can generate energy can be carried out at room temperature. - The theoretical process involves deuterium (H-2) with palladium or other metals. - This process produces minimal waste. - This theory is controversial, and most scientists think it is impossible.
1 sievert (Sv) =
1 J of radiation/kg = 1 Gy
1 gray (Gy) =
1 J/kg • Radiation dose absorbed by living tissue • Amount of energy deposited per unit of mass of human tissue
kilograms per amu
1.6606 * 10^-27 = 1 amu
1 Gy
100 rad
Mass Defect
29 + 34 < 63 the sum of the masses of the nucleons minus the mass of the atom. - The mass defect is always positive. - Mass defects can be expressed in amu or kilograms.
1 curie (ci) =
3.7 x 10^9 nuclear decay/sec • The number of disintegrations of radioactive atoms in a radioactive material over a period of time • The amount of radioactive materials released into the environment
1 rad =
= 0.01 Gy
1 becquerel (Bq) =
= 1 nuclear decay/sec
Examples of Fusion Reactions
A hydrogen-2 nucleus, which is one proton and one neutron, collides with a nucleus with two neutrons to form a nucleus.
Chemical Reactions Versus Nuclear Reactions
Chemical reactions: - involve interactions between electrons with no change in mass Nuclear reactions: - involve the SPLITTING apart of nuclei. - SEEMINGLY violate the law of conservation of mass. - release more energy than in chem reactions. - yield thousands of times more energy per gram compared to chemical reactions.
beta decay
Emission of electron or positron (an electron with a positive charge), both have a charge but negligible mass Can penetrate paper but not metal foil
How are energy and mass connected during the formation of a mass?
Energy is released, so the mass is reduced
Which occurs in the stars? nuclear fusion or fission?
Fusion
Which of the isotopes are radioactive?
H-3 or C-14 and anything above 200
why must the final product of a decay series be stable?
If the daughter isotope is unstable, it will decay. NOT: Each decay results in a net loss of particles.
Explain why isotopes of the same element behave differently in nuclear reactions but not in chemical reactions.
Isotopes of the same element differ only in neutron numbers. Nuclear reactions involve changes to the protons or neutrons in an atom's nucleus, but not changes to its electrons. Chemical reactions involve changes to the electrons in atoms, but not changes to its protons or neutrons. Isotope behavior only differs when a reaction involves neutrons.
Which of these statements explains the difference between nuclear binding energy and the strong nuclear force?
Nuclear binding energy is the energy needed to separate nuclear particles. The strong nuclear force holds an atom's protons and neutrons together. Nuclear binding energy can be calculated using E = mc2.
Cold Fusion Controversy
Stanley Pons and Martin Fleischmann claimed they were able to create energy thru fusion at room temp • # of neutrons measured from experiment were NOT consistent with expected numbers during fusion reactions • The presence of helium, which is a product of fusion reactions, was not measured. • The results of a similar experiment had CONFLICTING and inconclusive results but were ignored by the 2 scientists. • The scientific community was NOT able to test this study's validity
Why do nuclear reactions release more energy than chemical reactions?
The force that binds together protons and neutrons is stronger than the force that attracts and repels protons and neutrons
film badge
a badge made of photographic film, which can be used to measure a worker's exposure to radiation. - a device used for monitoring individual cumulative exposure to ionizing radiation
dosimeter
a badge that records exposure to radiation that is worn when taking x-rays
decay series
a chain of decay reactions beginning with a radioactive isotope. Radioisotopes continue to decay until a stable nucleus is reached
Geiger counter
a device used to measure radiation by detecting alpha or beta particles or gamma rays. - An amplifying device that indicates the presence of ionizing particles - A device that permits determination of alpha and beta radiation emitted from a substance
scintillation counter
a device used to measure radiation by measuring quantities of light emitted from a sensor. - A device that permits determination of alpha and beta radiation emitted from a substance
which would result in radioactive decay? a neutron-to-proton ratio of 1:1 in a small nucleus a neutron-to-proton ratio of 1:2 in a large nucleus
a neutron-to-proton ratio of 1:2 in a large nucleus
cloud chamber
a particle detector used to detect radiation in a sealed chamber
photon
a particle of light
nucleon
a proton or neutron
type of radiation that is safe on the skin, but super harmful if it reaches the inside of your body
alpha
Types of Radioactive Decay
alpha , beta , gamma
After one half-life
amount remaining = (1/2)^1
• After two half-lives
amount remaining = (1/2)^2 = 1/4
After 3 half-lifes
amount remaining = (1/2)^3 = 1/8
After n half-lives:
amount remaining = (1/2)^n
subcritical mass
an amount of fissionable material TOO SMALL TO SUSTAIN a constant rate of fission; reaction SLOWS and eventually STOPS
supercritical mass
an amount of fissionable material that produces an ACCELERATING rate of fission.
Transuranium Elements
an element with an atomic number greater than 92. - All are radioactive - Most elements with atomic number less than or equal to 92 are stable or have long half-lives - All were originally produced in a laboratory.
daughter isotope
an isotope formed from the radioactive decay of another isotope known as the parent isotope. The product that is NOT the alpha particle :)
parent isotope
an isotope that undergoes radioactive decay
Rutherford bombarded nitrogen gas with alpha particles, causing some of the nitrogen to change into oxygen by a process of
artificial transmutation NOT: alpha decay
which type of reaction is caused by particle accelerators?
artificial transmutation NOT: alpha decay
the radiation people protect themselves by wearing aluminum
beta radiation
which releases large amounts of eneryg?
both fusion and fission
Steam generator
converts water to steam, using the thermal energy from the reactor vessel
What most likely creates an unstable isotope?
equal #s of protons and neutrons in a large nucleus.
which device is best used for measuring the presence of radiation in large moving objects where constant monitoring is impossible?
film badge
Which time frame correctly describes the range of half-lives?
fractions of a second to billions of years
turbine
has blades that rotate like a fan in response to expanding steam.
nuclear fusion forms masses
heavier than helium, He (so
How do you know if a substance is radioactive?
if it contains unstable nuclei and the nuclei split over time
which statement about half-lives is ture
it measures the tendency of a radioisotope to decay
which has a high activaiton energy. Fusion or fission?
nuclear FUSION
Which Produces dangerous radioactive waste. Fusion or fission?
nuclear fission
How many new reactions can one neutron initiate?
one neutron can only initiate 1 reaction
which radiation is used to treat cancer?
photons
rem =
rad x Q • Measures biological risk and exposure to radiation • Radiation weighting factor (Q): the ability to transfer energy to the body • 1 for photons • 1 for electrons • 2 for protons • 20 for alpha particles, fission fragments, and heavy ions • 2 to 20 for neutrons, depending on the energy level
Decay chains exist because
radioactive elements can decay into stable or unstable elements.
Radioactive decay
s the spontaneous release of energy and particles from the nucleus of an unstable atom. - Isotopes of an element have different stabilities. - For example, 16 of 19 neon isotopes are unstable and will undergo radioactive decay.
Critical mass
the amount of fissionable material capable of sustaining a constant rate of fission
[artificial] Transmutation
the conversion of an atom of one element into an atom of another element.
Nuclear binding energy
the energy required to split the nucleus into separate protons and neutrons. • Strong nuclear force binds protons and neutrons together in the nucleus. The mass of an atom's nucleus is less than the sum of the masses of nucleons
strong nuclear force
the force responsible for binding protons and neutrons together in the nucleus. Nuclear reactions produce thousands of times more energy than chemical reactions.
generator
the generator is driven by the turbine. The generator converts mechanical energy to electrical energy.
Nuclear fission
the process in which a heavy nucleus is split into two large fragments of comparable mass to form more stable and smaller nuclei, resulting in the release of great amounts of energy - radioactive waste is produced. - It occurs naturally but not explosively. Notice that the total atomic numbers and mass numbers are _________ on both sides of the equation.
Radioactive decay 2
the process in which an unstable nucleus loses energy by emitting energy and particles. The energy given off by an unstable nucleus is called radiation - Nucleus achieves greater stability - Elemental identity of nucleus changes
nuclear fusion
the process in which lighter atomic nuclei combine to form a more stable, heavier nucleus, resulting in the release of great amounts of energy. • It has high activation energy. • It does not produce radioactive waste. • It is not currently plausible as an energy source on . • It occurs constantly in starsnu
chain reaction
the self-sustaining fission reaction spread by neutrons that occurs in nuclear reactors and bombs. - Neutrons from one fission reaction trigger more fission reactions. - the products of one reaction are the reactants in the next reaction.
Half-life
the time required for half the radioactive nuclei in a sample to decay • All radioisotopes have a half-life. • Half-lives are constant for each isotope • Half-lives vary dramatically from isotope to isotope. • Half-lives are NOT affected by temperature, pressure, density, or concentration. • The half-life is not an exact measure of the decay of an individual atom. • Half-lives range in length from tiny fractions of a second to billions of years. • No known relationship exists between isotopes and half-lives.
reactor vessel
where nuclear fission occurs. it contains fission reactions and releases thermal energy.
Radioisotopes
• A radioisotope is an atom w/ an unstable nucleus that will go through radioactive decay. • Each time a radioisotope goes through radioactive decay, it captures or releases particles to become an isotope of a different element. • The process continues until a stable isotope is formed.
alpha decay
• Emission of alpha particle , which contains two neutrons and two protons • Alpha particles represented by 4 2He • Least penetrating; cannot penetrate paper
gamma decay
• Emission of photon (the smallest possible quantity of light), which has no charge or mass • Highest energy; requires thick lead to shield
Calculating Half-Life from Mass
• Given initial and final masses, find the proportion of the sample remaining. • Half the mass will be lost with each half-life. • Calculate the half-life by figuring out how many halves were lost.
Biological effects of radiation on living cells may result in three outcomes:
• Injured or damaged cells could repair themselves, resulting in no residual damage. • The cells could die and be replaced through normal biological processes. • The cells could incorrectly repair themselves, resulting in biophysical changes.
Applications of Radiation
• Irradiation to kill germs • smoke detectors • Nuclear power • medical diagnostics, such as X-rays • Medical treatments
Converting Mass Defect into Nuclear Binding Energy
• The nucleus of an atom has lower potential than its individual components. • Energy is released when an atom is formed, reducing the mass. • To separate the nucleus, restore the energy. • The energy released is equal to the energy of the mass defect. • To calculate the nuclear binding energy: - convert the mass defect into kilograms . - use Einstein's equation
Radiation Treatments for Cancer
• They emit powerful X-ray energy. • Treatments stop cancerous cells from multiplying by: • shrink and kill tumors • stopping the growth of cancer cells. • decreasing pressure and pain. • Side effects include fatigue and sunburn like injuries. • They are delivered internally or externally
Control rods:
• are physical cylinders that can be moved in or out of a nuclear reactor vessel. • are inert and do not undergo fission themselves. • absorb neutrons produced during fission reactions. • decrease the fission process when dropped down into the reactor. (dropping = decreases electricity) • increase the fission process when raised up out of the reactor. (raise = increase electricity)
Each fission event:
• produces one or more neutrons. • leads to more reactions as neutrons initiate more fission events. • A chain reaction • can produce a cascading effect if two or more neutrons are produced with each event.
Nuclear chemists study:
• radioactive elements. • nuclear reactions. • absorption of radiation. • production and use of radioactive sources. • nuclear power. • the presence or level of radionuclides.
which drives power plants? fusion or fission?
Nuclear fission
The Cause of Radioactive Decay
Nuclear stability: - depends on neutron:proton ratio - depends on size of nucleus. As the size of the nucleus increases, a greater ratio of neutrons to protons is needed to stabilize the nucleus. Large nuclei with 84 or more protons are not stable.
The Importance of Half-Lives
Radioisotopes are used as "tracers" in nuclear scanning. • Short half-lives avoid damaging living tissue. • Technetium-99m has a half-life of 6 hours. Nuclear waste has a long half-life. • Iodine-129 has a half-life of 15.7 million years.
Radioactivity units
SI: Becquerel (Bq) Common unit: Curie (Ci)
Absorbed Dose unit
SI: gray (Gy) Common unit: rad
Dose Equivalent / Biological Risk Measurement unit
SI: sievert (Sv) Common unit: rem
