8.1 Ionic, Covalent, and Metallic Bonding
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Ionic vs Covalent vs Metallic Bonding
| BONDING | ||
|---|---|---|
| IONIC | COVALENT | METALLIC |
| Metal / NonmetalTransfer of e-Δ Electronegativity > 1.7 | Nonmetal / NonmetalSharing of e-Δ Electronegativity < 1.7 | Metal / Metal“Sea of e-“ |
| PROPERTIES OF TYPES OF COMPOUNDS/SUBSTANCES | |||
|---|---|---|---|
| IONIC | MOLECULAR | NETWORK COVALENT | METALLIC |
| High m.p and b.p.BrittleLattice Energy α q1q2/r | Lower m.p. and b.p. | High m.p. and b.p.Ex. C(diamond)SiO2 | Conduct electricityConduct heatLusterMalleableDuctile |
Ionic Bonding
-Transfer of electrons between elements with significant differences in electronegativity
-Element with low ionization energy loses electron(s) (metal)
-Element with high electron affinity gains electron(s) (nonmetal)
-Usually between a metal and a nonmetal (but don’t forget about polyatomic ions)
Lattice Energy
-Energy required to separate an ionic compound into gaseous ions
-Serves as a measure of the strength of the ionic bonds
NaCl(s) → Na+(g) + Cl-(g) ΔE = 787kJ/mol
| RANKING LATTICE ENERGIES |
|---|
| 1. Higher for greater charges |
| 2. Higher for smaller ions |
Which in each pair has a higher lattice energy?
NaF vs MgO MgO vs CaS
Covalent Bonding
| COVALENT BONDING | |
|---|---|
| -Sharing of electrons between atoms with an electronegativity difference <1.7 (typically 2 nonmetals) | |
| Nonpolar (or Pure) Covalent Bond | Polar Covalent Bond |
| Δ Electronegativity <0.5 | Δ Electronegativity 0.5 < x < 1.7 |
| Generally, between two identical atoms or C-H | Have partial ionic character |