Chemical Bonding (College Board AP® Chemistry): Flashcards
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Define electronegativity.
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Cards in this collection (40)
Define electronegativity.
Electronegativity is the tendency of an atom to attract a pair of electrons when it forms a covalent bond, mainly involving valence electrons.
True or False?
Electronegativity increases going down a group in the periodic table.
False.
Electronegativity decreases down a group because the shielding effect increases — the greater distance between the nucleus and valence electrons weakens the Coulombic attraction, reducing the effective nuclear charge.
Why does electronegativity increase across a period?
As you move across a period, the number of protons increases, raising the effective nuclear charge. This strengthens the Coulombic attraction between the nucleus and the bonding electrons, so each successive atom pulls the shared pair more strongly.
.......... (F) is the most electronegative atom in the periodic table.
Fluorine (F) is the most electronegative atom in the periodic table.
True or False?
Noble gases appear on the Pauling electronegativity scale.
False.
Noble gases do not appear on the Pauling scale because they have a full valence shell and do not form covalent bonds under normal conditions.
What is the role of the shielding effect in determining electronegativity down a group?
As more electron shells are added going down a group, inner electrons shield the valence electrons from the nuclear charge. This reduces the effective nuclear charge felt by the valence electrons, weakening the nucleus's pull on bonding pairs and lowering electronegativity.
The .......... scale assigns numerical electronegativity values to each element and is used to predict bond polarity.
The Pauling scale assigns numerical electronegativity values to each element and is used to predict bond polarity.
Define nonpolar covalent bond.
A nonpolar covalent bond is a bond between two atoms with equal or near-equal electronegativity, resulting in approximately equal sharing of the electron pair. Bonds between identical atoms are always nonpolar.
In a polar covalent bond, the more electronegative atom acquires a .......... partial charge (δ).
In a polar covalent bond, the more electronegative atom acquires a negative partial charge (δ).
True or False?
A triple covalent bond involves three atoms each sharing one electron.
False.
A triple covalent bond involves two atoms sharing three pairs (six) of electrons — each atom contributes three valence electrons to the bond.
How does the electronegativity difference between two bonded atoms determine whether a bond is polar or nonpolar?
A polar covalent bond forms when two atoms have different electronegativity values, causing the shared electrons to be pulled toward the more electronegative atom. Polarity is a continuum — there is no fixed numerical threshold.
Define dipole moment.
A dipole moment is a measure of the separation of positive and negative charges in a bond, created when one atom in a covalent bond attracts the shared electrons more strongly than the other.
True or False?
Polar covalent bonds have some ionic character.
True.
In polar covalent bonds, electrons are partially transferred toward the more electronegative atom, which gives the bond partial ionic character — the greater the electronegativity difference, the greater the ionic character.
Why does Cl2 form a nonpolar covalent bond?
Both chlorine atoms are identical, so their electronegativity difference is zero. With no tendency for either atom to pull the shared electrons preferentially, the bond has no dipole moment and is therefore nonpolar.
A covalent bond formed between two atoms with identical electronegativity, such as H2, N2 or F2, is classified as .......... because the electrons are shared equally between the atoms.
A covalent bond formed between two atoms with identical electronegativity, such as H2, N2 or F2, is classified as nonpolar because the electrons are shared equally between the atoms.
Define ionic bond.
An ionic bond is the electrostatic (Coulombic) force of attraction formed when a metal transfers one or more electrons to a nonmetal, producing oppositely charged ions.
An ionic bond forms when the electronegativity difference between two atoms is greater than .......... on the Pauling scale.
An ionic bond forms when the electronegativity difference between two atoms is greater than 2.0 on the Pauling scale.
True or False?
When Na+ forms in NaCl, it adopts the electron configuration of neon.
True.
Sodium loses one electron to form Na+, giving it the configuration 1s2 2s2 2p6 — the same as neon — which represents a full outer shell.
Why do ionic compounds have high melting and boiling points compared to most covalent compounds?
Ionic compounds are held together by strong Coulombic forces between oppositely charged ions in a lattice, requiring a large amount of energy to overcome and resulting in high melting and boiling points. Most covalent compounds have only weak intermolecular forces, which are much easier to overcome.
A nonmetal gains electrons during ionic bond formation to become a negatively charged ion called a .......... .
A nonmetal gains electrons during ionic bond formation to become a negatively charged ion called an anion.
How does solubility in water differ between ionic and nonpolar covalent compounds, and why?
Ionic compounds are generally soluble in water because the ions can form ion-dipole interactions with water molecules, breaking apart the lattice. Nonpolar covalent compounds are usually insoluble in water because they cannot interact with the polar water molecules — only polar covalent compounds may dissolve.
Define metallic bonding.
Metallic bonding is the Coulombic force of attraction between positively charged metal ions arranged in a lattice and the surrounding sea of delocalized electrons.
In a metallic solid, valence electrons that are no longer associated with individual atoms are described as .......... electrons.
In a metallic solid, valence electrons that are no longer associated with individual atoms are described as delocalized electrons.
True or False?
Metal atoms in a metallic lattice become positive ions by losing their valence electrons.
True.
Because atoms are tightly packed in a metallic lattice, they release their valence electrons into a shared pool, leaving behind positively charged metal cations.
Why are metals good conductors of electricity?
In a metal, delocalized electrons are free to move throughout the entire lattice structure. When a voltage is applied, these mobile electrons can carry charge from one end of the metal to the other, making metals effective electrical conductors.
True or False?
The term 'sea of electrons' refers to electrons that are fixed in position next to specific metal atoms.
False.
The 'sea of electrons' refers to delocalized electrons that move freely throughout the whole lattice — they are not bound to any particular atom.
Define bond length.
Bond length is the internuclear distance at which the potential energy between two bonded atoms is at its minimum — the equilibrium distance of a stable covalent bond.
The amount of energy required to break a covalent bond is called the .......... and corresponds to the difference between the minimum potential energy and zero.
The amount of energy required to break a covalent bond is called the bond energy and corresponds to the difference between the minimum potential energy and zero.
True or False?
The minimum potential energy on a potential energy diagram is always a negative value.
True.
When two atoms form a stable covalent bond, the system releases energy and the potential energy drops below zero. Bond energy is always reported as a positive value because breaking bonds is endothermic.
What happens to the potential energy when two atoms are brought very close together, and why?
The potential energy rises sharply (becomes very high) because the two positively charged nuclei and the two negatively charged electron clouds strongly repel one another at very short distances.
As bond order increases, bond length .......... and bond energy .......... .
As bond order increases, bond length decreases and bond energy increases.
True or False?
A C≡C triple bond is shorter than a C=C double bond.
True.
Higher bond order means more shared electron pairs hold the nuclei closer together. The C≡C bond (bond order 3, 120 pm) is shorter than C=C (bond order 2, 133 pm).
How does atomic radius affect bond length across the halogen diatomics?
As atomic radius increases down the halogen group, the bond length of the diatomic halogen molecule also increases. Larger atoms keep their nuclei further apart at equilibrium, so F2 has the shortest bond length and I2 the longest.
Define Coulomb's law (as applied to ionic bonding).
Coulomb's law states that the electrostatic force between two charged particles is proportional to the product of their charges and inversely proportional to the square of the distance between them: F = k(q1q2)/r2.
True or False?
According to Coulomb's law, the attractive force between a cation and an anion increases as ionic radius increases.
False.
Coulombic force is inversely proportional to r2. As ionic radius increases, the distance between charges increases, so the attractive force decreases.
In Coulomb's law (F = kq1q2/r2), the variable r represents the .......... between the two charges.
In Coulomb's law (F = kq1q2/r2), the variable r represents the distance between the two charges.
Why does MgCl2 have stronger Coulombic forces than NaCl?
Mg2+ carries a 2+ charge while Na+ carries only a 1+ charge. Because Coulombic force is proportional to the product of the ion charges (q1 × q2), the larger charge on Mg2+ produces a stronger attraction to the Cl- anion.
True or False?
A greater Coulombic force between ions leads to a more negative minimum potential energy for the ionic bond.
True.
Stronger Coulombic attraction means the system releases more energy when the bond forms, resulting in a deeper (more negative) potential energy well and higher lattice energy.
Between NaCl and KCl, which has the stronger Coulombic force of attraction, and why?
NaCl has the stronger Coulombic force because Na+ has a smaller ionic radius than K+ — despite both carrying a 1+ charge, the smaller radius places the charges closer together, increasing the force according to Coulomb's law (F ∝ 1/r2).
The greater the Coulombic force between ions, the greater the .......... (also known as lattice energy).
The greater the Coulombic force between ions, the greater the bond energy (also known as lattice energy).
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