Periodic Trends - MCAT Physical
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Which of the following elements has the greatest atomic radius?
Which of the following elements has the greatest atomic radius?
Atomic radius can be determined using the periodic trends. Atomic radius increases to the left of a period and down a group of the periodic table. Electronegativity, in contrast, increases to the right of a period and up a group of the periodic table. Relating the two, we can see that the greater the atomic radius, the weaker its electronegativity because the electrons are farther away from the nucleus and are unable to feel the attractive force of the protons in the nucleus.
Atomic radius can be determined using the periodic trends. Atomic radius increases to the left of a period and down a group of the periodic table. Electronegativity, in contrast, increases to the right of a period and up a group of the periodic table. Relating the two, we can see that the greater the atomic radius, the weaker its electronegativity because the electrons are farther away from the nucleus and are unable to feel the attractive force of the protons in the nucleus.
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Which of the following elements has the highest electronegativity?
Which of the following elements has the highest electronegativity?
Remember that electronegativity increases as you approach the top right corner of the periodic table. Since oxygen is the farthest right and the highest up on the perioidic table out of these choices, we conclude that it has the highest electronegativity.
Remember that electronegativity increases as you approach the top right corner of the periodic table. Since oxygen is the farthest right and the highest up on the perioidic table out of these choices, we conclude that it has the highest electronegativity.
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Which of the following elements has the greatest effective nuclear charge?
Which of the following elements has the greatest effective nuclear charge?
The effective nuclear charge is the attractive charge a valence electron feels from the nucleus. As you move from left to right along a period, and more positive charges (protons) fill up the nucleus, the more attraction the valence electron feels. As you move down a group, you jump into the next electron shell, thus shielding the valence electrons from the inner positive charge, and decreasing the effective nuclear charge.
Because chlorine is in the same period as phosphorus and sodium, but has the most protons in its shell (the most right within the same period) it has the greatest effective nuclear charge. Additionally, because chlorine is in the same group as bromine, but is higher up on the periodic table, it has a greater effective nuclear charge, making it the correct answer.
The effective nuclear charge is the attractive charge a valence electron feels from the nucleus. As you move from left to right along a period, and more positive charges (protons) fill up the nucleus, the more attraction the valence electron feels. As you move down a group, you jump into the next electron shell, thus shielding the valence electrons from the inner positive charge, and decreasing the effective nuclear charge.
Because chlorine is in the same period as phosphorus and sodium, but has the most protons in its shell (the most right within the same period) it has the greatest effective nuclear charge. Additionally, because chlorine is in the same group as bromine, but is higher up on the periodic table, it has a greater effective nuclear charge, making it the correct answer.
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Which of the given atoms has the lowest electron affinity?
Which of the given atoms has the lowest electron affinity?
Beryllium, calcium, strontium, and radium are all alkaline earth metals in the same group of the periodic table.
The electron affinity, a measure of the energy released when an atom gains an electron (an exothermic reaction), decreases from the top of a group (column) to the bottom. The trends in electron affinity can be correlated with ionization energy. When a smaller atom gains an electron, the force between the electron and nucleus is greater than in a larger atom; thus, more energy is released when this “bond” between the nucleus and electron is formed in a smaller atom than in a larger atom, meaning that smaller atoms will have greater electron affinity. Radium is the farthest down the group of alkaline earth metals, and will have the largest atomic radius of the answer choices, giving it the lowest electron affinity.
Beryllium, calcium, strontium, and radium are all alkaline earth metals in the same group of the periodic table.
The electron affinity, a measure of the energy released when an atom gains an electron (an exothermic reaction), decreases from the top of a group (column) to the bottom. The trends in electron affinity can be correlated with ionization energy. When a smaller atom gains an electron, the force between the electron and nucleus is greater than in a larger atom; thus, more energy is released when this “bond” between the nucleus and electron is formed in a smaller atom than in a larger atom, meaning that smaller atoms will have greater electron affinity. Radium is the farthest down the group of alkaline earth metals, and will have the largest atomic radius of the answer choices, giving it the lowest electron affinity.
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Which of the given atoms has the greatest electron affinity?
Which of the given atoms has the greatest electron affinity?
Sodium, aluminum, phosphorus, and chlorine are all in the same row (period) of the periodic table.
The electron affinity, a measure of the energy released when an atom gains an electron (an exothermic reaction), increases from left to right across the periodic table because when a smaller atom gains an electron, the force between the electron and nucleus is greater than with a larger atom. More energy is released when this “bond” between the nucleus and electron is formed. Chlorine has the smallest atomic radius of the answer choices because it is located farthest to the right of the period; thus, chlorine will also have the greatest attractive force between its nucleus and electrons, giving it the highest electron affinity.
Sodium, aluminum, phosphorus, and chlorine are all in the same row (period) of the periodic table.
The electron affinity, a measure of the energy released when an atom gains an electron (an exothermic reaction), increases from left to right across the periodic table because when a smaller atom gains an electron, the force between the electron and nucleus is greater than with a larger atom. More energy is released when this “bond” between the nucleus and electron is formed. Chlorine has the smallest atomic radius of the answer choices because it is located farthest to the right of the period; thus, chlorine will also have the greatest attractive force between its nucleus and electrons, giving it the highest electron affinity.
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Which of the given elements has the greatest electronegativity?
Which of the given elements has the greatest electronegativity?
Electronegativity, defined as the tendency of an atom to attract an electron, increases from left to right across a period, and the bottom of each group to the top. The most electronegative element is fluorine (F). This is because an electron that can be attracted to fluorine has the greatest ratio of attractive nuclear force to repulsive force by other electrons. Essentially, fluorine is the most stable ion with a negative-one charge. It is small, allowing the nuclear protons to maintain the attractive force on the electron, and it has an octet, giving it the absolute maximum ionic stability possible.
Electronegativity, defined as the tendency of an atom to attract an electron, increases from left to right across a period, and the bottom of each group to the top. The most electronegative element is fluorine (F). This is because an electron that can be attracted to fluorine has the greatest ratio of attractive nuclear force to repulsive force by other electrons. Essentially, fluorine is the most stable ion with a negative-one charge. It is small, allowing the nuclear protons to maintain the attractive force on the electron, and it has an octet, giving it the absolute maximum ionic stability possible.
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Which of the given elements has the lowest electronegativity?
Which of the given elements has the lowest electronegativity?
Electronegativity, defined as the tendency of an atom to attract an electron, increases from left to right across a period, and from the bottom of a group to top. The least electronegative (sometimes called most electropositive) element is francium (Fr). This is because an electron that can be attracted to francium has the lowest ratio of attractive nuclear force to repulsive force by other electrons in the atom. Essentially, the distance between the attractive nuclear protons is too great for the attractive force to overcome the repulsion of the orbiting electron cloud. Francium will not be stable if it gains an electron, and is much more stable if it loses an electron and forms an octet as a positive ion.
Electronegativity, defined as the tendency of an atom to attract an electron, increases from left to right across a period, and from the bottom of a group to top. The least electronegative (sometimes called most electropositive) element is francium (Fr). This is because an electron that can be attracted to francium has the lowest ratio of attractive nuclear force to repulsive force by other electrons in the atom. Essentially, the distance between the attractive nuclear protons is too great for the attractive force to overcome the repulsion of the orbiting electron cloud. Francium will not be stable if it gains an electron, and is much more stable if it loses an electron and forms an octet as a positive ion.
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Which of the following elements is the most electronegative?
Which of the following elements is the most electronegative?
The correct answer is chlorine. The most electronegative elements are those in the upper right of the periodic table, with the exception of the noble gases. Electronegativity describes how easily an element will gain an electron. The halogens (second to last group) "want" an extra electron to complete their valence shell. Iodine and chlorine are both halogens. Chlorine, however, has a smaller atomic radius, and therefore a smaller distance between the protons and outer electrons. Chlorine thus has a stronger attraction for an additional electron due to the greater effective nuclear attraction.
The correct answer is chlorine. The most electronegative elements are those in the upper right of the periodic table, with the exception of the noble gases. Electronegativity describes how easily an element will gain an electron. The halogens (second to last group) "want" an extra electron to complete their valence shell. Iodine and chlorine are both halogens. Chlorine, however, has a smaller atomic radius, and therefore a smaller distance between the protons and outer electrons. Chlorine thus has a stronger attraction for an additional electron due to the greater effective nuclear attraction.
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Which of the following would have the greatest atomic radius?
Which of the following would have the greatest atomic radius?
Atomic radius increases down each group of the periodic table and toward the left of each period. Since the elements listed are all in the same group, iodine would have the greatest atomic radius because it farther down the period compared to the others.
Atomic radius increases down each group of the periodic table and toward the left of each period. Since the elements listed are all in the same group, iodine would have the greatest atomic radius because it farther down the period compared to the others.
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Which of the following alkali metals has the greatest atomic radius?
Which of the following alkali metals has the greatest atomic radius?
The trend for atomic radius is to increase going from top to bottom, as additional valence shells are added to the atom. Out of the answer choices, rubidium has the highest energy valence shell.
With a single electron in the fifth energy level, krypton will have the highest number of energy levels of the group I elements listed.
When moving across a period, atomic radius will decrease as the number of protons increases. These protons increase the attraction between the high-energy electrons and the nucleus, effectively "shrinking" the electron cloud.
The trend for atomic radius is to increase going from top to bottom, as additional valence shells are added to the atom. Out of the answer choices, rubidium has the highest energy valence shell.
With a single electron in the fifth energy level, krypton will have the highest number of energy levels of the group I elements listed.
When moving across a period, atomic radius will decrease as the number of protons increases. These protons increase the attraction between the high-energy electrons and the nucleus, effectively "shrinking" the electron cloud.
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Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
A scientist is studying flourine. Which of the following is a possible electronegativity value for flourine?
Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
A scientist is studying flourine. Which of the following is a possible electronegativity value for flourine?
Flourine must have an electronegativity value higher than oxygen. Remember your periodic trends: electronegativity increases as we move up and to the right on the periodic table. We are told in the passage that the electronegativity of oxygen is 3.44, therefore, our answer must be 3.9.
Flourine must have an electronegativity value higher than oxygen. Remember your periodic trends: electronegativity increases as we move up and to the right on the periodic table. We are told in the passage that the electronegativity of oxygen is 3.44, therefore, our answer must be 3.9.
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Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
Electronegativity is associated with another function, electron affinity. What is true of electron affinity?
Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
Electronegativity is associated with another function, electron affinity. What is true of electron affinity?
Chlorine has a great thermodynamic desire to capture an electron, thus taking on the electronic structure of a stable noble gas. This causes chlorine to release energy when it captures an electron as it becomes more stable.
Sodium, on the other hand, would prefer to lose an electron and gain the configuration of a noble gas. Adding an electron would however award some stability to sodium, due to the complete s orbital that this would ensue.
Second electron affinity is usually encountered for such elements as oxygen and sulfur, which form anions with the addition of two electrons. The first electron affinity gives you O- or S-, and so it takes significant energy to add another electron to an already negative ion.
Chlorine has a great thermodynamic desire to capture an electron, thus taking on the electronic structure of a stable noble gas. This causes chlorine to release energy when it captures an electron as it becomes more stable.
Sodium, on the other hand, would prefer to lose an electron and gain the configuration of a noble gas. Adding an electron would however award some stability to sodium, due to the complete s orbital that this would ensue.
Second electron affinity is usually encountered for such elements as oxygen and sulfur, which form anions with the addition of two electrons. The first electron affinity gives you O- or S-, and so it takes significant energy to add another electron to an already negative ion.
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Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
Electronegativity is closely associated with the principle of ionization energy. Which of the following defines ionization energy?
Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
Electronegativity is closely associated with the principle of ionization energy. Which of the following defines ionization energy?
Even though adding an electron would generate an ion (anion), ionization energy is defined as the energy needed to remove an electron.
Even though adding an electron would generate an ion (anion), ionization energy is defined as the energy needed to remove an electron.
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Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
Electronegativity is closely associated with the principle of ionization energy. Which of the following is true of second, third, and successive ionization energies?
Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
Electronegativity is closely associated with the principle of ionization energy. Which of the following is true of second, third, and successive ionization energies?
As you ionize atoms, you generate charged ionic species. These charges will resist further ionization (cations will more strongly attract the electrons you are trying to pull away). Noble gas configurations are particularly stable, so you would expect a large increase in needed energy to ionize away from this state.
As you ionize atoms, you generate charged ionic species. These charges will resist further ionization (cations will more strongly attract the electrons you are trying to pull away). Noble gas configurations are particularly stable, so you would expect a large increase in needed energy to ionize away from this state.
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Using your knowledge of periodic trends, which statement is incorrect?
Using your knowledge of periodic trends, which statement is incorrect?
The second ionization energy of a neutral atom is always greater than the first.
Recall that ionization energy refers to the energy required to remove an electron from an atom. The first ionization energy will result in a cation. The reduced number of electrons in a cation allows them to be pulled closer to the nucleus by the positively charged protons, effectively decreasing the atomic radius and increasing the attractive force between the electrons and the nucleus. The energy required to remove a second electron must overcome this increased affinity, and will thus be greater than the first ionization energy.
The rest of the answers can be examined with a few simple trends kept in mind. Atomic radius increases to the left of a period and down a group. If two ions have the same electron configuration (like the chlorine anion and potassium cation), then the anion will have a larger radius because it has fewer protons to draw electrons inward. Electronegativity and electron affinity increase to the right across a period and up a group.
The second ionization energy of a neutral atom is always greater than the first.
Recall that ionization energy refers to the energy required to remove an electron from an atom. The first ionization energy will result in a cation. The reduced number of electrons in a cation allows them to be pulled closer to the nucleus by the positively charged protons, effectively decreasing the atomic radius and increasing the attractive force between the electrons and the nucleus. The energy required to remove a second electron must overcome this increased affinity, and will thus be greater than the first ionization energy.
The rest of the answers can be examined with a few simple trends kept in mind. Atomic radius increases to the left of a period and down a group. If two ions have the same electron configuration (like the chlorine anion and potassium cation), then the anion will have a larger radius because it has fewer protons to draw electrons inward. Electronegativity and electron affinity increase to the right across a period and up a group.
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When looking at the periodic table of elements, what is the general trend for increasing electronegativity?
When looking at the periodic table of elements, what is the general trend for increasing electronegativity?
Electronegativity increases to the right and up when looking at the periodic table of elements, such that fourine is the most electronegative element. Following this general trend can help you determine the relative electronegativity between atoms within problems. Remember that periods run horizontally on the table and groups run vertically.
Electronegativity increases to the right and up when looking at the periodic table of elements, such that fourine is the most electronegative element. Following this general trend can help you determine the relative electronegativity between atoms within problems. Remember that periods run horizontally on the table and groups run vertically.
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For any given chemical reaction, one can draw an energy diagram. Energy diagrams depict the energy levels of the different steps in a reaction, while also indicating the net change in energy and giving clues to relative reaction rate.
Below, a reaction diagram is shown for a reaction that a scientist is studying in a lab. A student began the reaction the evening before, but the scientist is unsure as to the type of the reaction. He cannot find the student’s notes, except for the reaction diagram below.
Using NMR, the scientist in the passage determines that there is a negative halide ion present in the products when the reaction reaches step 5. Which of the following factors would tend to raise the energy level at step 5?
For any given chemical reaction, one can draw an energy diagram. Energy diagrams depict the energy levels of the different steps in a reaction, while also indicating the net change in energy and giving clues to relative reaction rate.
Below, a reaction diagram is shown for a reaction that a scientist is studying in a lab. A student began the reaction the evening before, but the scientist is unsure as to the type of the reaction. He cannot find the student’s notes, except for the reaction diagram below.
Using NMR, the scientist in the passage determines that there is a negative halide ion present in the products when the reaction reaches step 5. Which of the following factors would tend to raise the energy level at step 5?
If the halide was flouride, it would have a negative charge dispersed over a smaller cross sectional area than if it was any of the other halides. Flouride is the smallest possible halide, and thus has the highest energy because it concentrates negative charge on the smallest area.
If the halide was flouride, it would have a negative charge dispersed over a smaller cross sectional area than if it was any of the other halides. Flouride is the smallest possible halide, and thus has the highest energy because it concentrates negative charge on the smallest area.
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Place the following atoms in decreasing order of atomic radius.
Cl, Ar, K, Ca
Place the following atoms in decreasing order of atomic radius.
Cl, Ar, K, Ca
Atomic radius has two general trends which you should remember:
1. Atomic radius will decrease when moving left to right along a period.
2. Atomic radius will increase when moving down a group.
Since potassium (K) and calcium (Ca) are farther down the group than argon (Ar) and chlorine (Cl), we conclude that they are the largest atoms in the set. Because Ca is to the right of K, it is slightly smaller than K. As a result, K has the largest atomic radius in the set followed by Ca. Since Ar is to the right of Cl, Cl has a larger atomic radius than Ar.
The decreasing order is K, Ca, Cl, Ar.
Atomic radius has two general trends which you should remember:
1. Atomic radius will decrease when moving left to right along a period.
2. Atomic radius will increase when moving down a group.
Since potassium (K) and calcium (Ca) are farther down the group than argon (Ar) and chlorine (Cl), we conclude that they are the largest atoms in the set. Because Ca is to the right of K, it is slightly smaller than K. As a result, K has the largest atomic radius in the set followed by Ca. Since Ar is to the right of Cl, Cl has a larger atomic radius than Ar.
The decreasing order is K, Ca, Cl, Ar.
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Rank the following ions in order of decreasing atomic radius.
Rank the following ions in order of decreasing atomic radius.
First, you should see that all four of these ions have the same amount of electrons, resulting in a stable \[Kr\] electron shell. These ions differ, however, by the number of protons in their nuclei. Since the heavier ions have more protons pulling on the same amount of electrons, the atomic radius will be smaller, as the negative electrons are drawn inward toward the positive nucleus.
Sr2+ has the most protons in its nucleus out of this set, so it will have the smallest atomic radius. The atomic radius will increase with decreasing atomic number.
The correct order from largest to smallest is Se2-, Br-, Rb+, and Sr2+.
First, you should see that all four of these ions have the same amount of electrons, resulting in a stable \[Kr\] electron shell. These ions differ, however, by the number of protons in their nuclei. Since the heavier ions have more protons pulling on the same amount of electrons, the atomic radius will be smaller, as the negative electrons are drawn inward toward the positive nucleus.
Sr2+ has the most protons in its nucleus out of this set, so it will have the smallest atomic radius. The atomic radius will increase with decreasing atomic number.
The correct order from largest to smallest is Se2-, Br-, Rb+, and Sr2+.
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Which element would you expect to have the greatest second ionization energy?
Which element would you expect to have the greatest second ionization energy?
Ionization energy is the energy required by an element to remove a valence electron and gain a positive charge. Because alkali metals and alkaline earth metals have one and two valence electrons, respectively, their first ionization energies are both relatively low; shedding a valence electron and absorbing a positive charge actually stabilizes these elements.
Alkaline earth metals can easily release their second valence electron, and have relatively low second ionization energies. Removing this second electron gives these elements a noble gas electronic configuration. This is why the ions of alkaline earth metals are most commonly Mg2+ and Ca2+. In comparison, alkali metals cannot easily shed a second valence electron because it would require removing an electron from an already-filled valence shell. Because of this, alkali metals have extremely HIGH second ionization energies in comparison to alkaline earth metals.
Of the answer choices, potassium would have the highest second ionization energy because it is an alkali metal, rather than an alkaline earth metal.
Ionization energy is the energy required by an element to remove a valence electron and gain a positive charge. Because alkali metals and alkaline earth metals have one and two valence electrons, respectively, their first ionization energies are both relatively low; shedding a valence electron and absorbing a positive charge actually stabilizes these elements.
Alkaline earth metals can easily release their second valence electron, and have relatively low second ionization energies. Removing this second electron gives these elements a noble gas electronic configuration. This is why the ions of alkaline earth metals are most commonly Mg2+ and Ca2+. In comparison, alkali metals cannot easily shed a second valence electron because it would require removing an electron from an already-filled valence shell. Because of this, alkali metals have extremely HIGH second ionization energies in comparison to alkaline earth metals.
Of the answer choices, potassium would have the highest second ionization energy because it is an alkali metal, rather than an alkaline earth metal.
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