An ionic bond results from the electrostatic attraction between oppositely charged ions.
Correct Answer
True
True. Ionic bonding arises when electrons transfer from one atom to another, producing a cation and an anion that attract each other. The strength of this attraction depends on the ion charges and the distance between them.
Category: Ionic Bonding
Question 2
Ionic compounds are typically soft solids with low melting points.
Correct Answer
False
False. Ionic compounds are typically hard, brittle solids with high melting points, because the strong attractions between ions extend throughout the crystal. Melting requires a large amount of energy to overcome them.
Category: Ionic Bonding
Question 3
Two nonmetal atoms typically bond to each other by transferring electrons to form ions.
Correct Answer
False
False. Two nonmetal atoms have similar tendencies to attract electrons, so they typically share electrons in covalent bonds. Electron transfer to form ions is characteristic of a metal combining with a nonmetal.
Category: Ionic Bonding
Question 4
Ionic compounds conduct electricity when they are melted.
Correct Answer
True
True. In a molten ionic compound the ions are free to move, so they can carry electric current. In the solid state the ions are locked in place, so the solid does not conduct.
Category: Ionic Bonding
Question 5
Electronegativity generally increases from left to right across a period of the periodic table.
Correct Answer
True
True. Moving across a period, nuclear charge increases while atoms get smaller, so the nucleus attracts shared electrons more strongly. Fluorine, near the upper right, has the highest electronegativity.
Category: Bond Polarity
Question 6
Atoms near the bottom of a group attract bonding electrons more strongly than atoms at the top of the same group.
Correct Answer
False
False. Electronegativity generally decreases down a group, because the valence electrons are farther from the nucleus and more shielded. Atoms at the top of a group attract bonding electrons more strongly.
Category: Bond Polarity
Question 7
In a polar covalent bond, the more electronegative atom carries a partial negative charge.
Correct Answer
True
True. The more electronegative atom pulls the shared electrons closer, gaining a partial negative charge, while the other atom is left with a partial positive charge. This separation of charge is a bond dipole.
Category: Bond Polarity
Question 8
A triple bond between two atoms consists of three shared electrons.
Correct Answer
False
False. A triple bond consists of three shared pairs, which is six electrons. Each line in a Lewis structure stands for one shared pair of two electrons.
Category: Lewis Structures
Question 9
The sum of the formal charges on all atoms in a polyatomic ion equals the overall charge of the ion.
Correct Answer
True
True. Formal charges are bookkeeping that distributes the species' electrons among its atoms, so they must add up to the total charge. For a neutral molecule they add up to zero.
Category: Formal Charge and Resonance
Question 10
Resonance structures of a species differ in the positions of the atoms.
Correct Answer
False
False. Resonance structures keep every atom in the same position and differ only in where electrons, such as lone pairs and multiple bonds, are placed. Structures with different atom arrangements are different compounds or isomers.
Category: Formal Charge and Resonance
Question 11
Bond energy decreases as the number of shared electron pairs between the same two atoms increases.
Correct Answer
False
False. More shared pairs make a bond stronger and shorter, so a triple bond has a greater bond energy than a double bond, which is stronger than a single bond between the same atoms.
Category: Bond and Lattice Energy
Question 12
For ions of the same charges, lattice energy increases as the distance between the ion centers decreases.
Correct Answer
True
True. The attraction between ions is inversely related to the distance between them, so smaller ions pack closer and give a larger lattice energy. This is why MgF2 has a larger lattice energy than MgI2.
Category: Bond and Lattice Energy
Question 13
Doubling the charge on both the cation and the anion of an ionic compound doubles its lattice energy.
Correct Answer
False
False. Lattice energy is proportional to the product of the ion charges, so doubling both charges multiplies it by four, assuming similar ion distances. This is why MgO has roughly four times the lattice energy of LiF.
Category: Bond and Lattice Energy
Question 14
In VSEPR theory, a double bond counts as a single region of electron density.
Correct Answer
True
True. A single, double or triple bond to an atom each counts as one region of electron density, as does a lone pair. The number of regions determines the electron-pair geometry.
Category: Molecular Geometry
Question 15
In a trigonal bipyramidal electron-pair geometry, lone pairs occupy the axial positions.
Correct Answer
False
False. Lone pairs occupy the equatorial positions. An equatorial position has only two neighboring regions at 90 degrees, with the other two at 120 degrees, while an axial position has three neighbors at 90 degrees, so equatorial placement minimizes repulsion.
Category: Molecular Geometry
Question 16
Repulsion between two lone pairs is stronger than repulsion between two bonding pairs.
Correct Answer
True
True. Lone pairs are held by only one nucleus and spread out more, so they repel more strongly. The order of repulsion is lone pair-lone pair, then lone pair-bonding pair, then bonding pair-bonding pair.
Category: Molecular Geometry
Question 17
XeF4 has a tetrahedral molecular structure.
Correct Answer
False
False. XeF4 has six electron regions on xenon, four bonds and two lone pairs. The lone pairs sit opposite each other, so the molecular structure is square planar.
Category: Molecular Geometry
Question 18
When a central atom has no lone pairs, its electron-pair geometry and molecular structure are the same.
Correct Answer
True
True. Molecular structure describes only the positions of atoms, so it differs from the electron-pair geometry only when lone pairs occupy some regions. With no lone pairs, every region holds an atom.
Category: Molecular Geometry
Question 19
CO2 is a polar molecule because each of its C=O bonds is polar.
Correct Answer
False
False. CO2 is nonpolar. Its C=O bonds are polar, but the linear shape places the two bond dipoles in opposite directions so they cancel.
Category: Molecular Polarity
Question 20
H2O is polar because its bent shape keeps the O-H bond dipoles from canceling.
Correct Answer
True
True. The two polar O-H bonds point in directions that do not oppose each other, so their dipoles add to give a net dipole moment. A linear water molecule would be nonpolar.
Category: Molecular Polarity