College Chem 8.1-8.5 Quiz

Bond Energy

Energy required to break a bond.

Why Atoms Bond

Atoms bond to lower total energy by gaining, losing, or sharing electrons.

Ionic Bond

Bond formed by electron transfer between a metal and nonmetal, creating oppositely charged ions.

Ionic Bond Stability

Ionic bonds have the greatest thermal stability due to strong electrostatic attraction.

Covalent Bond

Bond formed when atoms share electrons.

Bond Length

Distance at which repulsive and attractive forces balance to give lowest energy.

Coulomb's Law (Force)

Electrostatic force equals k(q₁q₂)/r².

Energy of Interaction Formula

E = 2.31×10⁻¹⁹ J·nm (Q₁Q₂ / r).

Energy Sign for Opposite Charges

Negative energy value—indicates attraction and increased stability.

Electronegativity

Ability of an atom in a molecule to attract electrons to itself.

Nonpolar Covalent Bond

Electrons shared equally; no partial charges.

Polar Covalent Bond

Electrons shared unequally; creates δ+ and δ− ends.

Ionic Bond (Polarity Spectrum)

Complete electron transfer resulting in full charges.

Effect of Electronegativity Difference

Greater difference = more polar bond.

Bond Polarity Order (Lowest → Highest)

H-H < S-H < H-Cl < H-O < H-F.

Dipole Moment

Occurs when a polar molecule aligns in an electric field.

Dipole Arrow Direction

Arrow points toward δ− end; tail at δ+ end.

Why Ions Form

To achieve a full valence shell and become isoelectronic with a noble gas.

Cation Definition

Atom that loses electrons; smaller than parent atom.

Anion Definition

Atom that gains electrons; larger than parent atom.

Isoelectronic Ions

Ions with the same number of electrons.

Isoelectronic Size Trend

Size decreases as nuclear charge increases.

Isoelectronic Example (Smallest → Largest)

Al³⁺ < Mg²⁺ < Na⁺ < F⁻ < O²⁻.

Lattice Energy

Energy released when gaseous ions form an ionic solid.

Sign of Lattice Energy

Negative (exothermic).

Factors Increasing Lattice Energy

Higher ion charges and smaller ionic radii.

Reason Ionic Compounds Form

Lattice energy release makes the overall process exothermic and stable.

Born-Haber Cycle Step 1

Convert elements to gaseous atoms (sublimation).

Born-Haber Cycle Step 2

Form ions (ionization energy and electron affinity).

Born-Haber Cycle Step 3

Combine ions (lattice energy).

Born-Haber Cycle Step 4

Add all energies for overall energy change.

Lattice Energy Analogy

Deep "gravity well" that makes the final solid much lower in energy.