Covalent Properties and Forces February 2015

How do you tell if a molecule is polar?

Properties of Covalent Compounds Differences in properties is a result of differences in attractive forces In a covalent compound Bond between atoms is relatively strong Bond between molecules is relatively weak Bonds between molecules are known as intermolecular forces or van der Waals forces

Intermolecular Forces Dispersion force Between nonpolar molecules Dipole-Dipole force Between oppositely charged ends of two polar molecules More polar the molecules the stronger the dipole- dipole force is Hydrogen Bond Between hydrogen end of one dipole and a F, O, or N atom on another dipole

Properties from forces Low melting points and boiling points Exist as gases or vaporize readily at room temperature Hardness depends on intermolecular force Relatively soft solids Solid phase Form crystal lattice Crystal shape depends on molecular shape

Covalent Network Solids Atoms interconnected by a network of covalent bonds Quartz and diamond Contrast molecular solids Typically brittle Non conductors of heat or electricity Extremely hard Diamond Carbon atom bonded to 4 other carbons Tetrahedral crystal – extremely hard and very high melting point

Comic Assignment due Friday 2/11 STORY - Choose one type of bonding and write “A Day in the Life of an Atom” story describing what it's like to be an atom that forms your chosen bond type. The story should incorporate at least 5 properties from your bonding. (you may do a song or poem as well) COMIC STRIP - Choose one type of bonding and write a comic strip with 3+ frames. The comic should incorporate at least 3 properties. SINGLE-FRAME CARTOON - Draw a single-frame cartoon for each type of bonding. Each cartoon should incorporate at least one key property from your Bonding.

Example