Atomic Nucleus - MCAT Chemical and Physical Foundations of Biological Systems
Card 1 of 91
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
What is the force responsible for attracting neutrons to the nuclei of neutron poisons?
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
What is the force responsible for attracting neutrons to the nuclei of neutron poisons?
Tap to reveal answer
The subatomic particles in an atom's nucleus, protons and neutrons, are held together by their own force called the strong nuclear force. Strong nuclear forces act in a somewhat counterintuitive way, and only over very short distances. The strong force is what allows protons to overcome their electrical repulsion to one another and exist together in the nucleus.
The subatomic particles in an atom's nucleus, protons and neutrons, are held together by their own force called the strong nuclear force. Strong nuclear forces act in a somewhat counterintuitive way, and only over very short distances. The strong force is what allows protons to overcome their electrical repulsion to one another and exist together in the nucleus.
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In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
Xe-135 is a fission product of U-235 after it absorbs a neutron. An alternative fission reaction allows U-235 to produce Ba-141 and three neutrons. If all that is produced in this fission reaction is Ba-141, three neutrons, and one other species, which of the following could be that one other species?
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
Xe-135 is a fission product of U-235 after it absorbs a neutron. An alternative fission reaction allows U-235 to produce Ba-141 and three neutrons. If all that is produced in this fission reaction is Ba-141, three neutrons, and one other species, which of the following could be that one other species?
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This is a tricky question, because it requires two steps. The first step is to recognize that the question specifies that U-235 absorbs a neutron via fission, so it becomes U-236. U-236 then breaks down into three neutrons, Ba-141, and Kr-92, because the total mass must not change.
Uranium has 92 protons, meaning that U-236 has 144 neutrons (236 – 92 = 144). Barium has 56 protons, meaning that Ba-141 must have 85 neutrons.
The identity of the unknown compound is given by the total protons (92) minus the protons in barium (56).
92 – 56 = 36
The unknown compound has 36 protons, meaning it must be Kr. The remaining neutrons must make up the remaining mass of the krypton isotope. There are 144 neutrons total, 85 given to barium, and 3 lost during reaction.
144 – (85 + 3) = 56
Krypton has 56 neutrons and 36 protons, giving it a total mass of 92.
This is a tricky question, because it requires two steps. The first step is to recognize that the question specifies that U-235 absorbs a neutron via fission, so it becomes U-236. U-236 then breaks down into three neutrons, Ba-141, and Kr-92, because the total mass must not change.
Uranium has 92 protons, meaning that U-236 has 144 neutrons (236 – 92 = 144). Barium has 56 protons, meaning that Ba-141 must have 85 neutrons.
The identity of the unknown compound is given by the total protons (92) minus the protons in barium (56).
92 – 56 = 36
The unknown compound has 36 protons, meaning it must be Kr. The remaining neutrons must make up the remaining mass of the krypton isotope. There are 144 neutrons total, 85 given to barium, and 3 lost during reaction.
144 – (85 + 3) = 56
Krypton has 56 neutrons and 36 protons, giving it a total mass of 92.
← Didn't Know|Knew It →
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
How does a nuclear fusion reaction compare to the nuclear fission reaction described in the passage?
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
How does a nuclear fusion reaction compare to the nuclear fission reaction described in the passage?
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Both reactions have the potential to produce energy, and both reactions have unstable intermediates. Fission reactions have unstable intermediates in the form of species like Xe-135, which the passage describes as being reactive with neutrons to become a different chemical species. Similarly, fusion reactions fuse smaller nuclei into unstable larger nuclei that subsequently give off energy upon their decay.
Both reactions have the potential to produce energy, and both reactions have unstable intermediates. Fission reactions have unstable intermediates in the form of species like Xe-135, which the passage describes as being reactive with neutrons to become a different chemical species. Similarly, fusion reactions fuse smaller nuclei into unstable larger nuclei that subsequently give off energy upon their decay.
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In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
In Xe-135, if each neutron and proton were separated and organized into 135 separate particles, then weighed and the masses summed precisely, the total of their masses would be equal to 135 atomic mass units.
Which of the following is true of the nucleus of Xe-135 if it were weighed on its own?
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
In Xe-135, if each neutron and proton were separated and organized into 135 separate particles, then weighed and the masses summed precisely, the total of their masses would be equal to 135 atomic mass units.
Which of the following is true of the nucleus of Xe-135 if it were weighed on its own?
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The concept of mass deficit dictates that nuclear subatomic particles typically have lower mass in their bound state than they do individually. If you took the total mass of each unbound constituent, it would be higher than the mass of the bound nucleus. This is the case regardless of whether Xe-135 interacts with another chemical species.
The concept of mass deficit dictates that nuclear subatomic particles typically have lower mass in their bound state than they do individually. If you took the total mass of each unbound constituent, it would be higher than the mass of the bound nucleus. This is the case regardless of whether Xe-135 interacts with another chemical species.
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In the nucleus, the accumulation of positive charges creates an electrostatic repulsion, known as the electromagnetic force. With the repulsive force that is generated, what is responsible for binding atoms together?
In the nucleus, the accumulation of positive charges creates an electrostatic repulsion, known as the electromagnetic force. With the repulsive force that is generated, what is responsible for binding atoms together?
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The binding energy of atoms is due in large part to the nuclear force, or strong force, which is the most powerful of the four universal forces.
Because the magnitude of the strong force is so large, it is able to overcome the electromagnetic force that is generated by the repulsion of like charges. Atoms exist in other parts of the universe beyond Earth, so the gravitational force is clearly not responsible. Neutrons have "neutral" charge, but that does not mean they are able to "neutralize" positive or negative charges.
The binding energy of atoms is due in large part to the nuclear force, or strong force, which is the most powerful of the four universal forces.
Because the magnitude of the strong force is so large, it is able to overcome the electromagnetic force that is generated by the repulsion of like charges. Atoms exist in other parts of the universe beyond Earth, so the gravitational force is clearly not responsible. Neutrons have "neutral" charge, but that does not mean they are able to "neutralize" positive or negative charges.
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The mass of a certain nucleus is 
. If the nucleus contains 24 protons and 27 neutrons, calculate its mass defect.
The mass of a certain nucleus is
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When protons and neutrons combine to form the nucleus of an atom, they generally have less total energy than the energies of the individual nucleons combined. This difference is known as the mass defect. In this case, the nucleus has 24 protons, each with a mass of 
, and 27 neutrons, each with a mass of 
.
The mass defect will be the difference between this predicted mass and the actual measured mass.
When protons and neutrons combine to form the nucleus of an atom, they generally have less total energy than the energies of the individual nucleons combined. This difference is known as the mass defect. In this case, the nucleus has 24 protons, each with a mass of
The mass defect will be the difference between this predicted mass and the actual measured mass.
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Which of the following is not a characteristic of nuclear fission?
Which of the following is not a characteristic of nuclear fission?
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Fission of heavy elements is exothermic; it releases energy because the products are closer to the peak of the binding energy curve than the original nucleus was. In other words, the products are more tightly bound and have more negative binding energies.
In contrast, fission is endothermic for lighter elements because their fission products are farther from the peak of the binding energy curve (the products are less tightly bound). So, fission of lighter elements would require an energy input in order to occur, making light-element fission endothermic.
All other listed answers are true statements.
Fission of heavy elements is exothermic; it releases energy because the products are closer to the peak of the binding energy curve than the original nucleus was. In other words, the products are more tightly bound and have more negative binding energies.
In contrast, fission is endothermic for lighter elements because their fission products are farther from the peak of the binding energy curve (the products are less tightly bound). So, fission of lighter elements would require an energy input in order to occur, making light-element fission endothermic.
All other listed answers are true statements.
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Which of the following cannot be the mass a nucleus containing two protons and two neutrons?
Which of the following cannot be the mass a nucleus containing two protons and two neutrons?
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The mass of a proton is 
and the mass of a neutron is 
. The mass of the given nucleus would be:
Because of mass deficit, it is not possible to get a mass greater than this value. The mass of a nucleus is always less than the sum of the masses of the parts.
The mass of a proton is
Because of mass deficit, it is not possible to get a mass greater than this value. The mass of a nucleus is always less than the sum of the masses of the parts.
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Nuclear attraction is a force between which two subatomic particles?
Nuclear attraction is a force between which two subatomic particles?
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Nuclear attraction is a force that holds together the molecules in the nucleus of an atom. Remember that there are a total of three subatomic particles in an atom: protons, neutrons, and electrons. Protons are positively charged, neutrons are neutral, and electrons are negatively charged. Of the three subatomic particles, only protons and neutrons are found inside the nucleus. Nuclear attraction must occur between a neutron and a proton. This force counteracts repulsion between protons to hold the nucleus together. Electrons are found in electron shells outside the nucleus and do not participate in nuclear attraction.
Nuclear attraction is a force that holds together the molecules in the nucleus of an atom. Remember that there are a total of three subatomic particles in an atom: protons, neutrons, and electrons. Protons are positively charged, neutrons are neutral, and electrons are negatively charged. Of the three subatomic particles, only protons and neutrons are found inside the nucleus. Nuclear attraction must occur between a neutron and a proton. This force counteracts repulsion between protons to hold the nucleus together. Electrons are found in electron shells outside the nucleus and do not participate in nuclear attraction.
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Which of the following is true about nuclear attraction force?
I. It occurs between two quarks
II. It occurs between two hadrons
III. It is classified as a strong force
Which of the following is true about nuclear attraction force?
I. It occurs between two quarks
II. It occurs between two hadrons
III. It is classified as a strong force
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Nuclear forces occur between protons and neutrons in the nucleus of an atom. Recall that quarks are elementary particles that make up composite particles called hadrons. Protons and neutrons are types of hadrons; therefore, nuclear forces occur between two hadrons.
There are four major types of fundamental forces: gravitational force, electromagnetic force, weak force, and strong force. Gravitational force is the attractive force between two bodies, electromagnetic force is a combination of the force between charges and magnetic force, weak force is the force between a W boson and a Z boson, and strong force is the force that occurs between two quarks. Nuclear forces between protons and neutrons are an effect created by the strong force between two quarks; however, nuclear forces are not classified as a type of strong force.
Nuclear forces occur between protons and neutrons in the nucleus of an atom. Recall that quarks are elementary particles that make up composite particles called hadrons. Protons and neutrons are types of hadrons; therefore, nuclear forces occur between two hadrons.
There are four major types of fundamental forces: gravitational force, electromagnetic force, weak force, and strong force. Gravitational force is the attractive force between two bodies, electromagnetic force is a combination of the force between charges and magnetic force, weak force is the force between a W boson and a Z boson, and strong force is the force that occurs between two quarks. Nuclear forces between protons and neutrons are an effect created by the strong force between two quarks; however, nuclear forces are not classified as a type of strong force.
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Choose the best answer for the following question.
You have a 
sample of an unknown substance with a half-life of 3 days. After 9 days how much of the substance remains?
Choose the best answer for the following question.
You have a
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Since the half-life of the sample is 3 days long, throughout the course of 9 days, the sample will undergo a half-life cycle 3 times. This means we have to half the mass of the original sample 3 times.
We originally start with 
After 3 days: 
After 6 days: 
After 9 days: 
Another way to solve these types of problems is using this formula: 
where 
is the number of half lives.
thus 
or 
of the original sample remains. 
Therefore after 9 days, there will be 
of the original sample remaining.
Since the half-life of the sample is 3 days long, throughout the course of 9 days, the sample will undergo a half-life cycle 3 times. This means we have to half the mass of the original sample 3 times.
We originally start with
After 3 days:
After 6 days:
After 9 days:
Another way to solve these types of problems is using this formula:
thus
Therefore after 9 days, there will be
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Which of the following is not accurate regarding spontaneous fission reactions?
Which of the following is not accurate regarding spontaneous fission reactions?
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In fission a large atom, with low binding energy per nucleon, splits into two approximately equal smaller atoms, which are more stable due to greater binding energy per nucleon. All the other properties mentioned are accurate.
In fission a large atom, with low binding energy per nucleon, splits into two approximately equal smaller atoms, which are more stable due to greater binding energy per nucleon. All the other properties mentioned are accurate.
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In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
What is the force responsible for attracting neutrons to the nuclei of neutron poisons?
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
What is the force responsible for attracting neutrons to the nuclei of neutron poisons?
Tap to reveal answer
The subatomic particles in an atom's nucleus, protons and neutrons, are held together by their own force called the strong nuclear force. Strong nuclear forces act in a somewhat counterintuitive way, and only over very short distances. The strong force is what allows protons to overcome their electrical repulsion to one another and exist together in the nucleus.
The subatomic particles in an atom's nucleus, protons and neutrons, are held together by their own force called the strong nuclear force. Strong nuclear forces act in a somewhat counterintuitive way, and only over very short distances. The strong force is what allows protons to overcome their electrical repulsion to one another and exist together in the nucleus.
← Didn't Know|Knew It →
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
Xe-135 is a fission product of U-235 after it absorbs a neutron. An alternative fission reaction allows U-235 to produce Ba-141 and three neutrons. If all that is produced in this fission reaction is Ba-141, three neutrons, and one other species, which of the following could be that one other species?
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
Xe-135 is a fission product of U-235 after it absorbs a neutron. An alternative fission reaction allows U-235 to produce Ba-141 and three neutrons. If all that is produced in this fission reaction is Ba-141, three neutrons, and one other species, which of the following could be that one other species?
Tap to reveal answer
This is a tricky question, because it requires two steps. The first step is to recognize that the question specifies that U-235 absorbs a neutron via fission, so it becomes U-236. U-236 then breaks down into three neutrons, Ba-141, and Kr-92, because the total mass must not change.
Uranium has 92 protons, meaning that U-236 has 144 neutrons (236 – 92 = 144). Barium has 56 protons, meaning that Ba-141 must have 85 neutrons.
The identity of the unknown compound is given by the total protons (92) minus the protons in barium (56).
92 – 56 = 36
The unknown compound has 36 protons, meaning it must be Kr. The remaining neutrons must make up the remaining mass of the krypton isotope. There are 144 neutrons total, 85 given to barium, and 3 lost during reaction.
144 – (85 + 3) = 56
Krypton has 56 neutrons and 36 protons, giving it a total mass of 92.
This is a tricky question, because it requires two steps. The first step is to recognize that the question specifies that U-235 absorbs a neutron via fission, so it becomes U-236. U-236 then breaks down into three neutrons, Ba-141, and Kr-92, because the total mass must not change.
Uranium has 92 protons, meaning that U-236 has 144 neutrons (236 – 92 = 144). Barium has 56 protons, meaning that Ba-141 must have 85 neutrons.
The identity of the unknown compound is given by the total protons (92) minus the protons in barium (56).
92 – 56 = 36
The unknown compound has 36 protons, meaning it must be Kr. The remaining neutrons must make up the remaining mass of the krypton isotope. There are 144 neutrons total, 85 given to barium, and 3 lost during reaction.
144 – (85 + 3) = 56
Krypton has 56 neutrons and 36 protons, giving it a total mass of 92.
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In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
How does a nuclear fusion reaction compare to the nuclear fission reaction described in the passage?
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
How does a nuclear fusion reaction compare to the nuclear fission reaction described in the passage?
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Both reactions have the potential to produce energy, and both reactions have unstable intermediates. Fission reactions have unstable intermediates in the form of species like Xe-135, which the passage describes as being reactive with neutrons to become a different chemical species. Similarly, fusion reactions fuse smaller nuclei into unstable larger nuclei that subsequently give off energy upon their decay.
Both reactions have the potential to produce energy, and both reactions have unstable intermediates. Fission reactions have unstable intermediates in the form of species like Xe-135, which the passage describes as being reactive with neutrons to become a different chemical species. Similarly, fusion reactions fuse smaller nuclei into unstable larger nuclei that subsequently give off energy upon their decay.
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In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
In Xe-135, if each neutron and proton were separated and organized into 135 separate particles, then weighed and the masses summed precisely, the total of their masses would be equal to 135 atomic mass units.
Which of the following is true of the nucleus of Xe-135 if it were weighed on its own?
In the operation of nuclear reactors, engineers make use of substances known as neutron poisons. These are used to help store nuclear waste and slow nuclear reactions, but are also generated naturally in nuclear chain reactions as a by-product. This natural by-product can stop the desirable chain reaction present in a nuclear reactor used for power generation.
For example, in nuclear power plants, U-235 is used as a fuel. U-235 absorbs a neutron, and subsequently generates neutrons (which power the chain reaction) and Xe-135. Xe-135 is a well-known neutron poison, and thus can impact the continued chain reaction of a nuclear power plant if it becomes over abundant during power generation.
To help account for this, engineers have developed measurements to quantify the impact of Xe-135 on nuclear operations. For instance, the time during which there is an inability to start a reactor due to the buildup of Xe-135 is referred to as the precluded start-up time. Also, the amount of time that the reactor cannot override the effects of built up Xe-135 is called poison outage time. Perhaps the most important measure that engineers have developed is the _neutron absorption capacity (_σ), which is measured in units of barns and is a function of microscopic cross section. Xe-135 has a neutron absorption capacity of 2.00 * 106 barns, while another common poison, Sm-149, has a neutron absorption capacity of 74,500 barns.
In Xe-135, if each neutron and proton were separated and organized into 135 separate particles, then weighed and the masses summed precisely, the total of their masses would be equal to 135 atomic mass units.
Which of the following is true of the nucleus of Xe-135 if it were weighed on its own?
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The concept of mass deficit dictates that nuclear subatomic particles typically have lower mass in their bound state than they do individually. If you took the total mass of each unbound constituent, it would be higher than the mass of the bound nucleus. This is the case regardless of whether Xe-135 interacts with another chemical species.
The concept of mass deficit dictates that nuclear subatomic particles typically have lower mass in their bound state than they do individually. If you took the total mass of each unbound constituent, it would be higher than the mass of the bound nucleus. This is the case regardless of whether Xe-135 interacts with another chemical species.
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In the nucleus, the accumulation of positive charges creates an electrostatic repulsion, known as the electromagnetic force. With the repulsive force that is generated, what is responsible for binding atoms together?
In the nucleus, the accumulation of positive charges creates an electrostatic repulsion, known as the electromagnetic force. With the repulsive force that is generated, what is responsible for binding atoms together?
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The binding energy of atoms is due in large part to the nuclear force, or strong force, which is the most powerful of the four universal forces.
Because the magnitude of the strong force is so large, it is able to overcome the electromagnetic force that is generated by the repulsion of like charges. Atoms exist in other parts of the universe beyond Earth, so the gravitational force is clearly not responsible. Neutrons have "neutral" charge, but that does not mean they are able to "neutralize" positive or negative charges.
The binding energy of atoms is due in large part to the nuclear force, or strong force, which is the most powerful of the four universal forces.
Because the magnitude of the strong force is so large, it is able to overcome the electromagnetic force that is generated by the repulsion of like charges. Atoms exist in other parts of the universe beyond Earth, so the gravitational force is clearly not responsible. Neutrons have "neutral" charge, but that does not mean they are able to "neutralize" positive or negative charges.
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The mass of a certain nucleus is . If the nucleus contains 24 protons and 27 neutrons, calculate its mass defect.
The mass of a certain nucleus is
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When protons and neutrons combine to form the nucleus of an atom, they generally have less total energy than the energies of the individual nucleons combined. This difference is known as the mass defect. In this case, the nucleus has 24 protons, each with a mass of , and 27 neutrons, each with a mass of .
The mass defect will be the difference between this predicted mass and the actual measured mass.
When protons and neutrons combine to form the nucleus of an atom, they generally have less total energy than the energies of the individual nucleons combined. This difference is known as the mass defect. In this case, the nucleus has 24 protons, each with a mass of
The mass defect will be the difference between this predicted mass and the actual measured mass.
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Which of the following is not a characteristic of nuclear fission?
Which of the following is not a characteristic of nuclear fission?
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Fission of heavy elements is exothermic; it releases energy because the products are closer to the peak of the binding energy curve than the original nucleus was. In other words, the products are more tightly bound and have more negative binding energies.
In contrast, fission is endothermic for lighter elements because their fission products are farther from the peak of the binding energy curve (the products are less tightly bound). So, fission of lighter elements would require an energy input in order to occur, making light-element fission endothermic.
All other listed answers are true statements.
Fission of heavy elements is exothermic; it releases energy because the products are closer to the peak of the binding energy curve than the original nucleus was. In other words, the products are more tightly bound and have more negative binding energies.
In contrast, fission is endothermic for lighter elements because their fission products are farther from the peak of the binding energy curve (the products are less tightly bound). So, fission of lighter elements would require an energy input in order to occur, making light-element fission endothermic.
All other listed answers are true statements.
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Which of the following cannot be the mass a nucleus containing two protons and two neutrons?
Which of the following cannot be the mass a nucleus containing two protons and two neutrons?
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The mass of a proton is and the mass of a neutron is . The mass of the given nucleus would be:
Because of mass deficit, it is not possible to get a mass greater than this value. The mass of a nucleus is always less than the sum of the masses of the parts.
The mass of a proton is
Because of mass deficit, it is not possible to get a mass greater than this value. The mass of a nucleus is always less than the sum of the masses of the parts.
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