Bonding and Chemical Interactions
Answers to Concept Checks
1. Ionic bonds form between ions and involve gain or loss of electrons. Covalent bonds occur when electrons are shared between atoms.
2. Any three examples that form incomplete octets (H, He, Li, Be, B) or expanded octets (Period 3 and greater) are acceptable.
3. The polarity in a covalent bond is determined by differences in electronegativity between the two atoms involved.
1. Metals lose electrons because they have low ionization energies, while nonmetals gain electrons because they have high electron affinities. These processes are complementary, leading to the formation of an ionic bond.
2. Some characteristics of ionic compounds include high melting and boiling points due to electrostatic attractions, solubility of ions in water due to interactions with polar solvents, good conductors of heat and electricity, crystal lattice arrangement to minimize repulsive forces, and large electronegativity differences between ions, among other possible answers.
1. Bond strength is defined by the electrostatic attraction between nuclei and electrons; multiple bonds (higher bond order) increases strength. Bond length is a consequence of these attractions. The stronger the bond, the shorter it is. Bond energy is the minimum amount of energy needed to break a bond. The stronger the bond, the higher the bond energy.
2. Nonpolar covalent bonds form with ΔEN = 0 to 0.5. Polar covalent bonds form with ΔEN = 0.5 to 1.7. Ionic bonds form with ΔEN = 1.7 or higher.
4. PCl5: trigonal bipyramidal, MgF2: linear, AlF3: trigonal planar, UBr6: octahedral, SiH4: tetrahedral
1. Hydrogen bonding > dipole—dipole interactions > dispersion (London) forces
2. A dipole consists of a segment of a molecule with partial positive and partial negative regions. The positive end of one molecule is attracted to the negative end of another molecule, and vice-versa.
3. To experience hydrogen bonding, a molecule must contain a hydrogen bonded to a very electronegative atom (nitrogen, oxygen, or fluorine).