Nuclear Chemistry and Electrons - MCAT Chemical and Physical Foundations of Biological Systems
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What is the electron configuration of potassium after it obtains a +1 charge?
What is the electron configuration of potassium after it obtains a +1 charge?
Potassium (K) is orignially in the electron configuration of \[Ar\]4s1. To obtain a +1 charge it loses an electron, resulting in a configuration of \[Ar\].
Potassium (K) is orignially in the electron configuration of \[Ar\]4s1. To obtain a +1 charge it loses an electron, resulting in a configuration of \[Ar\].
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What is the electron configuration of Fe+?
What is the electron configuration of Fe+?
When an element loses an electron it is generally taken away from the highest electron shell. The electron configuration of iron (Fe) is 
. The 4s orbital is farther away from the nucleus than the 3d orbital, therefore the electron configuration of Fe+ will be 
.
When an element loses an electron it is generally taken away from the highest electron shell. The electron configuration of iron (Fe) is
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An atom with the electron configuration 1s22s22p6 could be any of the following except .
An atom with the electron configuration 1s22s22p6 could be any of the following except .
This particular configuration denotes a particle with ten total electrons. The sodium atom, with eleven electrons, is the only one listed that could not have this configuration. Ionized sodium, however, symbolized as Na+, does apply. (Be careful to distinguish neutral atoms and ions).
This particular configuration denotes a particle with ten total electrons. The sodium atom, with eleven electrons, is the only one listed that could not have this configuration. Ionized sodium, however, symbolized as Na+, does apply. (Be careful to distinguish neutral atoms and ions).
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Which of the following is the correct electronic configuration for vanadium?
Which of the following is the correct electronic configuration for vanadium?
When determining electronic configuration, the answer is made much easier by starting with the next smallest noble gas in brackets. As a result, \[Ar\] is an appropriate way to incorporate every previous electron before argon.
After argon, vanadium has five other electrons to distribute, and because vanadium is a transitional element, it will fill its 3d subshells before filling the 4p subshells. The 4s subshell is filled first, and the last three electrons are placed into the 3d subshells.
\[Ar\]3d34s2
When determining electronic configuration, the answer is made much easier by starting with the next smallest noble gas in brackets. As a result, \[Ar\] is an appropriate way to incorporate every previous electron before argon.
After argon, vanadium has five other electrons to distribute, and because vanadium is a transitional element, it will fill its 3d subshells before filling the 4p subshells. The 4s subshell is filled first, and the last three electrons are placed into the 3d subshells.
\[Ar\]3d34s2
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What is the correct electronic structure for 
?
What is the correct electronic structure for
Were this question asking for the electronic structure of magnesium (Mg) in its ground state, 
would be the correct answer; however, the 
charge on 
means that the molecule shed two valence electrons to achieve a more stable orbital. Those electrons will be shed from the outermost valence shell, which in this case is the 
shell; therefore, 
is correct.
Note that the ground state of magnesium will have twelve electrons (the same as its atomic number), while the ion will have ten.
Were this question asking for the electronic structure of magnesium (Mg) in its ground state,
Note that the ground state of magnesium will have twelve electrons (the same as its atomic number), while the ion will have ten.
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An electron in which of the following orbitals is closest to the nucleus?
An electron in which of the following orbitals is closest to the nucleus?
Nuclear orbitals will always fill from the innermost to the outermost subshells. Using the 
rule, we can approximate the order in which these orbitals will fill. Because electrons fill starting with the centermost orbitals, the electron that is closest to the nucleus will belong to the orbital that fills first.
corresponds to the principle quantum number, the first number in the given orbital location. 
is the azimuthal quantum number, and dictates the shape of the orbital.
5s and 3d produce the same number from the 
equation, but in the event of a tie we always pick the orbital with the lowest letter (s < p < d < f). The innermost orbital will be 5s.
Nuclear orbitals will always fill from the innermost to the outermost subshells. Using the
5s and 3d produce the same number from the
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Which of the following species is represented by the given electron configuration?
Which of the following species is represented by the given electron configuration?
Due to the phenomenon of half-orbital stability in the transition metals, electrons can easily move between 4s and 3d orbitals. The atom achieves greater stability from having only one atom in the 4s orbital, allowing a half-filled 3d orbital, as opposed to a full 4s orbital and four electrons in the 3d subshell.
For elements like chromium and copper, which could have valence shell configurations of 4s23d4 and _4s_23d9, respectively, an electron from the 4s orbital jumps down to the 3d orbital to harness added stability from the half-filled orbital. The given electron configuration is that of chromium.
Note that you can also solve this question by counting the electrons to determine the atomic number. In this case, the electrons add up to 24, indicating the twenty-fourth element: chromium.
Due to the phenomenon of half-orbital stability in the transition metals, electrons can easily move between 4s and 3d orbitals. The atom achieves greater stability from having only one atom in the 4s orbital, allowing a half-filled 3d orbital, as opposed to a full 4s orbital and four electrons in the 3d subshell.
For elements like chromium and copper, which could have valence shell configurations of 4s23d4 and _4s_23d9, respectively, an electron from the 4s orbital jumps down to the 3d orbital to harness added stability from the half-filled orbital. The given electron configuration is that of chromium.
Note that you can also solve this question by counting the electrons to determine the atomic number. In this case, the electrons add up to 24, indicating the twenty-fourth element: chromium.
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Which element has the most valence electrons?
Which element has the most valence electrons?
Valence electrons will be housed in the outer shell (highest numbered orbital) of the electron configuration.
Calcium: 
Magnesium: 
Zinc: 
Copper: 
Arsenic: 
Calcium, magnesium, and zinc all have two valence electrons in their highest energy orbital. Copper has only one valence electron. Arsenic has five total valence electrons in the fourth shell.
Valence electrons will be housed in the outer shell (highest numbered orbital) of the electron configuration.
Calcium:
Magnesium:
Zinc:
Copper:
Arsenic:
Calcium, magnesium, and zinc all have two valence electrons in their highest energy orbital. Copper has only one valence electron. Arsenic has five total valence electrons in the fourth shell.
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What is the correct electron configuration of 
?
What is the correct electron configuration of
An atom that has a charge of 
has lost two electrons. The two lost are always the valence electrons, which are most easily taken from the molecule. Strontium has a normal electron configuration with 38 electrons. In shorthand notation, this would be:
Losing two valence electrons will remove the 5s electrons. This leave the configuration as:
This makes sense because krypton has a stable valence octet. Strontium is stable as an ion, meaning that it will also have an octet, allowing it to match the configuration for krypton.
An atom that has a charge of
Losing two valence electrons will remove the 5s electrons. This leave the configuration as:
This makes sense because krypton has a stable valence octet. Strontium is stable as an ion, meaning that it will also have an octet, allowing it to match the configuration for krypton.
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Which two elements have the same number of electrons in the 3d shell?
Which two elements have the same number of electrons in the 3d shell?
Valence electrons in the d subshell can be odd because a half-filled d orbital is more stable than one with three or four electrons. While strontium, titanium, and vanadium have two electrons in their 4s orbitals, chromium has one in the 4s shell and puts five in the 3d shell.
This creates a half-filled 4s and 3d shells, which are more stable than a full 4s shell and partial 3d shell. Chromium and manganese thus have the same number of 3d electrons: five.
Valence electrons in the d subshell can be odd because a half-filled d orbital is more stable than one with three or four electrons. While strontium, titanium, and vanadium have two electrons in their 4s orbitals, chromium has one in the 4s shell and puts five in the 3d shell.
This creates a half-filled 4s and 3d shells, which are more stable than a full 4s shell and partial 3d shell. Chromium and manganese thus have the same number of 3d electrons: five.
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Which of the following is the correct notation for a sodium ion?
Which of the following is the correct notation for a sodium ion?
A neutral atom of sodium would contain eleven electrons to balance out the charge of the eleven protons in the nucleus. We are asked, however, for the configuration of a sodium ion. Sodium is an alkali metal, meaning that it will ionize by losing only one electron, gaining a charge of 
. By losing one electron, sodium drops from having eleven electrons to ten. We will need to select the answer that shows an electron removed form the outermost shell.
Neutral sodium: 
Sodium ion: 
A neutral atom of sodium would contain eleven electrons to balance out the charge of the eleven protons in the nucleus. We are asked, however, for the configuration of a sodium ion. Sodium is an alkali metal, meaning that it will ionize by losing only one electron, gaining a charge of
Neutral sodium:
Sodium ion:
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Which of the following is true about gaining and losing electrons in cobalt?
Which of the following is true about gaining and losing electrons in cobalt?
Cobalt is a transition metal; therefore, it is found in the D block of the periodic table. A ground state cobalt atom has an electron configuration of 
. The last orbitals that gain or lose electrons must be either the 
or 
orbitals, since these are the orbitals with highest energy and located farthest from the nucleus.
Recall that electrons are filled from orbitals of low energy to high energy. A 
orbital has a lower energy than a 
orbital. This means that when you are filling electrons, the last orbital you fill is the 
orbital. When you are assigning electrons to each orbital you assign two electrons to the 
orbital and then the remaining seven electrons to the five 
orbitals; therefore, 
orbitals are filled last when gaining electrons.
When an element loses electrons, the first orbital that loses electrons is the outermost orbital. This occurs because the attractive force of the nucleus on the electron will be weakest in the outermost orbital (because it is farthest away from nucleus); therefore, it will be easy to pull the electron away from the nucleus. In cobalt, the outermost orbital is the 
orbital (because it has the highest shell number). This means that electrons will be lost from the 
orbital before the 
orbital.
Notice that the orbital that gains electron last is not the same orbital that loses electrons first. Gaining electrons is dependent on the energy of the orbital, and losing electrons is dependent on the location of the orbital. The highest energy orbital will gain electron last and the outermost orbital will lose electron first.
Cobalt is a transition metal; therefore, it is found in the D block of the periodic table. A ground state cobalt atom has an electron configuration of
Recall that electrons are filled from orbitals of low energy to high energy. A
When an element loses electrons, the first orbital that loses electrons is the outermost orbital. This occurs because the attractive force of the nucleus on the electron will be weakest in the outermost orbital (because it is farthest away from nucleus); therefore, it will be easy to pull the electron away from the nucleus. In cobalt, the outermost orbital is the
Notice that the orbital that gains electron last is not the same orbital that loses electrons first. Gaining electrons is dependent on the energy of the orbital, and losing electrons is dependent on the location of the orbital. The highest energy orbital will gain electron last and the outermost orbital will lose electron first.
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A certain transition metal has an electron configuration such that its 
orbital only has one electron. What would be a valid conclusion about this element?
A certain transition metal has an electron configuration such that its
The question states that the element is a transition element and it only has one electron in its 
orbital. Recall that transition metals usually have two electrons in its 
orbital; however, some transition metals lose one of the electrons from their 
orbital and move it to one of their 
orbital. This occurs because of a phenomenon called half-shell stability. Half-shell stability states that an element is more stable when all the orbitals are half filled.
This is best exemplified by the transition metal chromium. The electron configuration of chromium, conventionally, would be 
. This means that chromium has two electrons in the 
orbital, one electron in four 
orbitals, and an empty 
orbital. Half-shell stability states that chromium is more stable if all five 
orbitals have an electron, rather than having an empty 
orbital; therefore, an electron from the 
orbital will be moved to the empty 
orbital to fulfill half-shell stability. This gives one electron in the 
orbital and one electron in each of the five 
orbitals.
Notice that half-shell stability is also observed in molybdenum (
) and tungsten (
). Molybdenum will have one electron in its 
orbital and one electron in each of its 
orbitals, and tungsten will have one electron in its 
orbital and one electron in each of its 
orbitals.
The question states that the element is a transition element and it only has one electron in its
This is best exemplified by the transition metal chromium. The electron configuration of chromium, conventionally, would be
Notice that half-shell stability is also observed in molybdenum (
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An oxygen atom and a fluorine atom have the same electron configuration as neon. Which of the following is true about these two atoms?
An oxygen atom and a fluorine atom have the same electron configuration as neon. Which of the following is true about these two atoms?
The question states that the oxygen and fluorine atoms have the same electron configuration as neon. The electron configuration for neon is 
, with ten total electrons and eight valence electrons. To match this configuration, both the oxygen and the fluorine atom must have eight valence electrons (two in the 
orbital and six in the 
orbital).
Recall that atoms in the oxygen group have six valence electrons, whereas halogens have seven valence electrons; therefore, oxygen has six and fluorine has seven valence electrons. To reach a total of eight valence electrons (octet) the oxygen atom must have gained two electrons, giving it a charge of 
. Similarly, fluorine must have gained one electron, giving it a charge of 
. Fluorine has half the of charge of oxygen because it gained half the amount of electrons to complete its octet.
The question states that the oxygen and fluorine atoms have the same electron configuration as neon. The electron configuration for neon is
Recall that atoms in the oxygen group have six valence electrons, whereas halogens have seven valence electrons; therefore, oxygen has six and fluorine has seven valence electrons. To reach a total of eight valence electrons (octet) the oxygen atom must have gained two electrons, giving it a charge of
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Which of the following are correct statements about binding energy?
I. Light nuclei experience an increase in binding energy by fusion, and heavy nuclei by fission
II. Binding energy is the amount of energy required to separate a nucleus into its individual nucleons
III. Radioactive decay processes tend to produce nuclei which have lower binding energies than the original nucleus
Which of the following are correct statements about binding energy?
I. Light nuclei experience an increase in binding energy by fusion, and heavy nuclei by fission
II. Binding energy is the amount of energy required to separate a nucleus into its individual nucleons
III. Radioactive decay processes tend to produce nuclei which have lower binding energies than the original nucleus
The first two statements are true. Statement III is false becuse radioactive decays tend to produce nuclei with higher binding energy per nucleon than the parent nucleus, since nuclei with higher binding energy are held together more tightly and thus are more stable.
The first two statements are true. Statement III is false becuse radioactive decays tend to produce nuclei with higher binding energy per nucleon than the parent nucleus, since nuclei with higher binding energy are held together more tightly and thus are more stable.
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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?
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?
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?
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?
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?
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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