Metallic Bonds and Intramolecular Forces

Metallic Bond Bond that exists between metal atoms Alloy – two or more different metal atoms bonded together

Electron Sea Model Metal atoms give up valence electrons and form + ions The released electrons move freely around the + metal ions

Properties of Metallic Bonds Good conductors of electricity – free electrons Malleable and ductile – not in rigid position so ions can be shaped and drawn into wires Conduct heat because of free electrons Lustrous – absorb and emit light in regular pattern due to free electrons

What Holds A Liquid Or Solid Together? In ionic compounds, all atoms are equally bonded together in the crystal What about covalent?

Two Types of Covalent Compounds Covalent Network Crystal - all atoms covalently bonded together equally - very strong and hard - ex: diamond, graphite

Covalent Molecular Substance - individual molecules attracted to one another through intramolecular forces - not anywhere near as strong as networks - ex: water

Intramolecular Forces Force of attraction between molecules in a covalent molecular substance Three types: Dipole – Dipole forces Hydrogen Bond London Dispersion forces

Dipole- Dipole Between polar molecules Positive pole of one ion attracted to the negative pole of another

Hydrogen Bonding Attraction between hydrogen atom in one molecule and an unshared pair of electrons on the atom of another molecule

London Dispersion Force Hold non-polar molecules together Caused by motion of electrons

Strength of Interaction Substances held together by ionic bonds or covalent network bonds are very rigidly connected: mostly solid at room temp and melt at very high temps Those held by dipole-dipole or hydrogen bonds are fairly strongly connected: liquid at room temp or solids that melt at low temps Those held by London dispersion forces are weakly connected: gases at room temp; need to be very cold to become liquid

Ionic vs. Covalent IonicCovalent Molecular Melting Point High Low Vaporize No Maybe CrystallineYes, hard & brittle Maybe, soft Dissolve in Water Yes Mostly no Conduct electricity when liquid Yes No Conduct electricity when dissolve in water Yes No