Chapter 8

1. Chapter 8 Allison Kim Eunwoo Kim Esther Park

2. Lewis Structure • shows how valence electrons are arranged among the atoms in the molecules • Only the valence electrons are included in Lewis Structure.

3. Octet Rule • Atoms tend to gain, lose, or share electrons until they are surrounded by eight valence electrons. • Exceptions: • Molecules containing odd number of electron • Molecules in which an atom has fewer than an octet of valence electrons • Molecules in which an atom has more than an actet of valence electrons

4. Ionic Bonding • Attraction between ions of unlike charge = stable ionic compounds • Lattice energy – energy required to completely separate a mole of a solid ionic compound into its gaseous ions • Lattice energy increase as the charges in the ions increase and as their radii decrease.

5. Covalent Bonding • Results from the sharing of electrons between two atoms • Single bond: one pair of electrons is shared • Double: two pairs of electrons are shared • Triple: three pairs of electrons are shared

6. Bond Polarity & Dipole Moments • Dipole – distance separates two electrical charges of equal magnitude but opposite sign • Dipole moment – quantitative measure of the magnitude of a dipole

7. Electronegativity • The ability of an atom in a molecule to attract shared electrons to itself • Ionization energy – measures how strongly a gaseous atom holds on to its electrons • Electron affinity – measure of how strongly an atom attracts additional electrons

8. Formal Charge • Formal Charge – charge the atom would have if all the atoms in the molecule had the same electronegativity

9. Resonance Structures • Occurs when more than one valid Lewis structure can be written for particular molecule

10. Strengths of covalent bonds • Δ= ΣD (bond broken) – ΣD (bond formed) • Ex. Δ = [D(C - H)+D(Cl - Cl)] – [D(C - Cl)+D(H - Cl)] = (413kJ + 242kJ) – (328kJ + 341kJ) Δ = - 104kJ