Molecules - AP Chemistry
Card 0 of 182
How many lone pairs of electrons exist on the following molecule?
BF3
How many lone pairs of electrons exist on the following molecule?
BF3
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.. ..
:F — B — F: Boron can have a violated octet (6 e-) and each F has 3 lone pairs
.. | .. for a total of 9 pairs of unpaired electrons
:F:
..
.. ..
:F — B — F: Boron can have a violated octet (6 e-) and each F has 3 lone pairs
.. | .. for a total of 9 pairs of unpaired electrons
:F:
..
Which of the following compounds contains an atom that does NOT satisfy the octet rule?
I. 
II. 
III. 
IV. 
Which of the following compounds contains an atom that does NOT satisfy the octet rule?
I.
II.
III.
IV.
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BCl3 only has six electrons around boron, while NO2 (with an odd number of electrons) would have only 7 electrons around the central nitrogen.
BCl3 only has six electrons around boron, while NO2 (with an odd number of electrons) would have only 7 electrons around the central nitrogen.
Which of the following elements will have two unpaired valence electrons?
Which of the following elements will have two unpaired valence electrons?
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Lewis dot diagrams can help us keep track on how the valence electrons will disperse themselves among orbitals in the atom. When drawing these diagrams, it is important to keep two things in mind.
1. The s orbital will be filled before the p orbital begins to be filled.
2. Electrons will never pair in the same orbital if an orbital of equal energy is unoccupied.
Knowing these two facts, we can predict which of the following elements will have two unpaired electrons.
Fluorine will have seven valence electrons, meaning that only one orbital will not be completely filled. 
Beryllium only has two valence electrons, but they will both be found in the 2s orbital, because it must be filled before the p orbitals can receive electrons. 
Nitrogen will have five valence electrons, so two will be found in the 2s orbital. The other three will be present in their own p orbitals, meaning nitrogen has three unpaired electrons. 
Neon will have eight valence electrons, fully filling the 2s and 2p orbitals. It will have no unpaires electrons. 
Carbon has one less valence electron than nitrogen, meaning that it will have two unpaired electrons in the p orbitals. 
Lewis dot diagrams can help us keep track on how the valence electrons will disperse themselves among orbitals in the atom. When drawing these diagrams, it is important to keep two things in mind.
1. The s orbital will be filled before the p orbital begins to be filled.
2. Electrons will never pair in the same orbital if an orbital of equal energy is unoccupied.
Knowing these two facts, we can predict which of the following elements will have two unpaired electrons.
Fluorine will have seven valence electrons, meaning that only one orbital will not be completely filled.
Beryllium only has two valence electrons, but they will both be found in the 2s orbital, because it must be filled before the p orbitals can receive electrons.
Nitrogen will have five valence electrons, so two will be found in the 2s orbital. The other three will be present in their own p orbitals, meaning nitrogen has three unpaired electrons.
Neon will have eight valence electrons, fully filling the 2s and 2p orbitals. It will have no unpaires electrons.
Carbon has one less valence electron than nitrogen, meaning that it will have two unpaired electrons in the p orbitals.
Which of the following is isoelectric with the cation 
?
Which of the following is isoelectric with the cation
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Isoelectronic means having the same electron configuration (i.e. the same number of electrons). 
and 
both have the same number of electrons (18), while sulfur has 16, phosphorous has 15, neon has 10, and the sodium cation has 10.
Isoelectronic means having the same electron configuration (i.e. the same number of electrons).
Which answer option correctly depicts the Lewis dot structure of sodium chloride?
Which answer option correctly depicts the Lewis dot structure of sodium chloride?
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When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.
Sodium and chlorine form an ionic bond, meaning that one atom will donate an electron and the other will receive it. This gives each atom a charge. Chlorine has seven valence electrons, while sodium has one valence electron. For each atom to arrive at an octet, sodium will need to lose one electron and chlorine will need to gain one electron. This would give chlorine a negative charge, and sodium a positive charge.
Thus, the answer is a sodium with a positive charge (due to one lost electron) and a chlorine with eight electrons and a negative charge (due to one electron gained).
When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.
Sodium and chlorine form an ionic bond, meaning that one atom will donate an electron and the other will receive it. This gives each atom a charge. Chlorine has seven valence electrons, while sodium has one valence electron. For each atom to arrive at an octet, sodium will need to lose one electron and chlorine will need to gain one electron. This would give chlorine a negative charge, and sodium a positive charge.
Thus, the answer is a sodium with a positive charge (due to one lost electron) and a chlorine with eight electrons and a negative charge (due to one electron gained).
What is the Lewis dot structure for 
?
What is the Lewis dot structure for
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When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.
In this case, boron actually has an incomplete octet. Though there are resonance forms in which boron has a full octet, when you calculate the formal charge of these configurations it will not be zero.
When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.
In this case, boron actually has an incomplete octet. Though there are resonance forms in which boron has a full octet, when you calculate the formal charge of these configurations it will not be zero.
Which of the following is an intrinsic physical property of a chemical substance?
Which of the following is an intrinsic physical property of a chemical substance?
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Intrinsic properties do not depend on the amount of a substance present. Mass, heat, and enthalpy are all dependent on the amount of substance.
Intrinsic properties do not depend on the amount of a substance present. Mass, heat, and enthalpy are all dependent on the amount of substance.
Which of the following is NOT true of the law of constant composition?
Which of the following is NOT true of the law of constant composition?
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The law of constant composition can't be applied to solutions because it only applies to pure samples. Solutions are not pure samples, since they contain more than just 1 compound.
The law of constant composition can't be applied to solutions because it only applies to pure samples. Solutions are not pure samples, since they contain more than just 1 compound.
A compound that is formed in the mechanism of a reaction but does not appear in the overall reaction is referred to as a(n) .
A compound that is formed in the mechanism of a reaction but does not appear in the overall reaction is referred to as a(n) .
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This is the very definition of an intermediate. It is formed in one step within the mechanism of the reaction, but then something else happens to it as the reaction continues to completion; thus, it does not show up in the overall reaction.
This is the very definition of an intermediate. It is formed in one step within the mechanism of the reaction, but then something else happens to it as the reaction continues to completion; thus, it does not show up in the overall reaction.
A compound is 
hydrogen and 
oxygen by mass. What is the name and molecular formula of this compound?
A compound is
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Knowing there is at least one hydrogen atom and one oxygen atom in this compound means the total molar mass must be at least 
. If we first assume 
is equivalent to only 1 mole of hydrogen, we get a total molar mass of 
. This number is too low to make logical sense.
Therefore, we must next assume there are 2 moles of hydrogen. Using this assumption, we can find the hypothetical molecular mass.
Use this molecular mass to calculate the mass of oxygen.
Therefore, there must be 2 moles of hydrogen and 2 moles of oxygen, making the molecular formula 
.
This compound is called peroxide.
Knowing there is at least one hydrogen atom and one oxygen atom in this compound means the total molar mass must be at least
Therefore, we must next assume there are 2 moles of hydrogen. Using this assumption, we can find the hypothetical molecular mass.
Use this molecular mass to calculate the mass of oxygen.
Therefore, there must be 2 moles of hydrogen and 2 moles of oxygen, making the molecular formula
This compound is called peroxide.
A compound is comprised only of carbon and hydrogen. The molar mass of the compound is 
and the compound is 
carbon by mass. What is the empirical formula?
A compound is comprised only of carbon and hydrogen. The molar mass of the compound is
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Use the molar mass and percent by mass of carbon to find the moles of carbon in the compound.
We know that the compound is made solely of carbon and hydrogen. This allows us to find the percent by mass of hydrogen.
Use the molar mass and the percent by mass of hydrogen to find moles of hydrogen in the compound.
The molecular formula is 
.
Because 7 and 16 have no common factors, the compound cannot be further reduced (in a numerical, not chemical sense). 
is also the empirical formula.
Use the molar mass and percent by mass of carbon to find the moles of carbon in the compound.
We know that the compound is made solely of carbon and hydrogen. This allows us to find the percent by mass of hydrogen.
Use the molar mass and the percent by mass of hydrogen to find moles of hydrogen in the compound.
The molecular formula is
Because 7 and 16 have no common factors, the compound cannot be further reduced (in a numerical, not chemical sense).
A compound is comprised of sulfur and element X. The compound has a molar mass of 
and is 
sulfur. Analysis shows the compound has twice as much sulfur as element X. Find the molecular and empirical formulas for the compound, including the identity of element X.
A compound is comprised of sulfur and element X. The compound has a molar mass of
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Use the molar mass and percent by mass of sulfur to find the moles of sulfur in the compound.
Since the compound consists of only sulfur and element X, we can subtract to find the percent by mass of element X.
Use the percent by mass to find the mass per mole of compound of element X.
Because we are told there are one-half as many moles of X as there are of sulfur, we know there are 2 moles of X (as compared to the 4 moles of sulfur). Divide the mass of element X by the moles of element X to find its atomic mass and its identity.
By consulting a periodic table, we can find that element X is silicon.
Therefore, the molecular formula is 
and the empirical formula is 
.
Use the molar mass and percent by mass of sulfur to find the moles of sulfur in the compound.
Since the compound consists of only sulfur and element X, we can subtract to find the percent by mass of element X.
Use the percent by mass to find the mass per mole of compound of element X.
Because we are told there are one-half as many moles of X as there are of sulfur, we know there are 2 moles of X (as compared to the 4 moles of sulfur). Divide the mass of element X by the moles of element X to find its atomic mass and its identity.
By consulting a periodic table, we can find that element X is silicon.
Therefore, the molecular formula is
A compound is comprised of sodium and element X. The compound has a molar mass of 
and is 
sodium by mass. The compound consists of a 1:1 ratio between sodium and element X. Find the molecular and empirical formulas of the compound, including the identity of element X.
A compound is comprised of sodium and element X. The compound has a molar mass of
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Use the molar mass and percent by mass of sodium to find the moles of sodium in the compound.
Since the compound consists of only sodium and element X, we can subtract to find the percent by mass of element X.
Use the percent by mass to find the mass per mole of compound of element X.
Because there is a 1:1 ratio, between sodium and element X, they must have an equal number of moles in the compound. Since there are 2 moles of sodium, there must also be 2 moles of element X. Divide the mass of element X by the moles of element X to find its atomic mass and its identity.
By consulting a periodic table, we can find that element X is oxygen.
Therefore element X is Oxygen.
Therefore, the molecular formula is 
and the empirical formula is 
.
Use the molar mass and percent by mass of sodium to find the moles of sodium in the compound.
Since the compound consists of only sodium and element X, we can subtract to find the percent by mass of element X.
Use the percent by mass to find the mass per mole of compound of element X.
Because there is a 1:1 ratio, between sodium and element X, they must have an equal number of moles in the compound. Since there are 2 moles of sodium, there must also be 2 moles of element X. Divide the mass of element X by the moles of element X to find its atomic mass and its identity.
By consulting a periodic table, we can find that element X is oxygen.
Therefore element X is Oxygen.
Therefore, the molecular formula is
How many lone pairs of electrons exist on the following molecule?
BF3
How many lone pairs of electrons exist on the following molecule?
BF3
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.. ..
:F — B — F: Boron can have a violated octet (6 e-) and each F has 3 lone pairs
.. | .. for a total of 9 pairs of unpaired electrons
:F:
..
.. ..
:F — B — F: Boron can have a violated octet (6 e-) and each F has 3 lone pairs
.. | .. for a total of 9 pairs of unpaired electrons
:F:
..
Which of the following compounds contains an atom that does NOT satisfy the octet rule?
I.
II.
III.
IV.
Which of the following compounds contains an atom that does NOT satisfy the octet rule?
I.
II.
III.
IV.
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BCl3 only has six electrons around boron, while NO2 (with an odd number of electrons) would have only 7 electrons around the central nitrogen.
BCl3 only has six electrons around boron, while NO2 (with an odd number of electrons) would have only 7 electrons around the central nitrogen.
Which of the following elements will have two unpaired valence electrons?
Which of the following elements will have two unpaired valence electrons?
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Lewis dot diagrams can help us keep track on how the valence electrons will disperse themselves among orbitals in the atom. When drawing these diagrams, it is important to keep two things in mind.
1. The s orbital will be filled before the p orbital begins to be filled.
2. Electrons will never pair in the same orbital if an orbital of equal energy is unoccupied.
Knowing these two facts, we can predict which of the following elements will have two unpaired electrons.
Fluorine will have seven valence electrons, meaning that only one orbital will not be completely filled.
Beryllium only has two valence electrons, but they will both be found in the 2s orbital, because it must be filled before the p orbitals can receive electrons.
Nitrogen will have five valence electrons, so two will be found in the 2s orbital. The other three will be present in their own p orbitals, meaning nitrogen has three unpaired electrons.
Neon will have eight valence electrons, fully filling the 2s and 2p orbitals. It will have no unpaires electrons.
Carbon has one less valence electron than nitrogen, meaning that it will have two unpaired electrons in the p orbitals.
Lewis dot diagrams can help us keep track on how the valence electrons will disperse themselves among orbitals in the atom. When drawing these diagrams, it is important to keep two things in mind.
1. The s orbital will be filled before the p orbital begins to be filled.
2. Electrons will never pair in the same orbital if an orbital of equal energy is unoccupied.
Knowing these two facts, we can predict which of the following elements will have two unpaired electrons.
Fluorine will have seven valence electrons, meaning that only one orbital will not be completely filled.
Beryllium only has two valence electrons, but they will both be found in the 2s orbital, because it must be filled before the p orbitals can receive electrons.
Nitrogen will have five valence electrons, so two will be found in the 2s orbital. The other three will be present in their own p orbitals, meaning nitrogen has three unpaired electrons.
Neon will have eight valence electrons, fully filling the 2s and 2p orbitals. It will have no unpaires electrons.
Carbon has one less valence electron than nitrogen, meaning that it will have two unpaired electrons in the p orbitals.
Which of the following is isoelectric with the cation ?
Which of the following is isoelectric with the cation
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Isoelectronic means having the same electron configuration (i.e. the same number of electrons). and both have the same number of electrons (18), while sulfur has 16, phosphorous has 15, neon has 10, and the sodium cation has 10.
Isoelectronic means having the same electron configuration (i.e. the same number of electrons).
Which answer option correctly depicts the Lewis dot structure of sodium chloride?
Which answer option correctly depicts the Lewis dot structure of sodium chloride?
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When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.
Sodium and chlorine form an ionic bond, meaning that one atom will donate an electron and the other will receive it. This gives each atom a charge. Chlorine has seven valence electrons, while sodium has one valence electron. For each atom to arrive at an octet, sodium will need to lose one electron and chlorine will need to gain one electron. This would give chlorine a negative charge, and sodium a positive charge.
Thus, the answer is a sodium with a positive charge (due to one lost electron) and a chlorine with eight electrons and a negative charge (due to one electron gained).
When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.
Sodium and chlorine form an ionic bond, meaning that one atom will donate an electron and the other will receive it. This gives each atom a charge. Chlorine has seven valence electrons, while sodium has one valence electron. For each atom to arrive at an octet, sodium will need to lose one electron and chlorine will need to gain one electron. This would give chlorine a negative charge, and sodium a positive charge.
Thus, the answer is a sodium with a positive charge (due to one lost electron) and a chlorine with eight electrons and a negative charge (due to one electron gained).
What is the Lewis dot structure for ?
What is the Lewis dot structure for
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When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.
In this case, boron actually has an incomplete octet. Though there are resonance forms in which boron has a full octet, when you calculate the formal charge of these configurations it will not be zero.
When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.
In this case, boron actually has an incomplete octet. Though there are resonance forms in which boron has a full octet, when you calculate the formal charge of these configurations it will not be zero.
Which of the following is an intrinsic physical property of a chemical substance?
Which of the following is an intrinsic physical property of a chemical substance?
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Intrinsic properties do not depend on the amount of a substance present. Mass, heat, and enthalpy are all dependent on the amount of substance.
Intrinsic properties do not depend on the amount of a substance present. Mass, heat, and enthalpy are all dependent on the amount of substance.