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