Chemical Bonding revised

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So ionic compounds that have ions with large charges will have higher melting/boiling points

Slide 63

Molecular Forces

Of the molecular compounds, dipoles that form hydrogen bonds are the strongest

Dipole-dipole forces are weaker than hydrogen bonds

Non-polar molecules that have London dispersion forces are the weakest

Slide 64

Therefore, hydrogen bonded substances have the highest melting/boiling points, dipole-dipole have lower melting/boiling points, and non-polar substances have the lowest melting/boiling points

Slide 65

Mechanical Properties of Solids

Metals are malleable because of the nature of metallic bonds (positive ions in a sea of electrons)

Ionic substances are brittle because if a layer of the crystal is shifted down one position, like ions will be aligned and repel

Non-polar molecular substances are usually soft and easily broken

Slide 66

Conductivity

The ability of a substance to transfer electrical current

For this to occur, charged particles (ions or electrons) must be able to move freely

Slide 67

Metals are good conductors because their electrons are free to move throughout the metallic structure

Ionic solids do not conduct electric current because the ions are held together in a rigid structure

Slide 68

Ionic substances that are dissolved in water are good conductors because the charged ions are free to move in the solution

Some network solids can conduct electricity because of delocalized electrons (graphite)

Molecular compounds cannot conduct electricity in pure form or dissolved in water

Slide 69

Review Questions

Pg. 137

#3,4,6-14, 16, 19, 21, 22, 25-29, 31, 34-39, 41, 43, 47, 48, 51, 57, 60

brdebenham@cbe.ab.ca