1. IB Topic 4: Bonding

2.  pure carbon is covalently bonded in three of different forms (allotropes) 1. graphite 2. diamond 3. fullerenes  To buy lots of super duper expensive carbon allotropes, CLICK HERECLICK HERE

3.  possesses a layer structure  the layers of carbon atoms are arranged in an repeating fashion

4.  more compact structure and dense than graphite  one of the hardest materials known

5.  highly stable chemically  most famous is the “buckeyball” › discovers awarded Nobel Prize in 1996 › over 1000 fullerene compounds have been made  composed of carbon atoms that form a hollow, cage-like structure › interesting feature of fullerenes is their ability to enclose other atoms

6.  forces that occur between molecules  much weaker than intramolecular (within the molecule) forces › it takes 464 kJ/mol to break the H-O bonds within a water molecule and only 19 kJ/mol to break the bonds between water molecules  the strength of the intermolecular forces determines the physical properties of the substance › melting, boiling, reacting, solubility, conductivity, volatility  this will be covered in next PowerPoint

9.  van der Walls YouTube (:20) van der Walls YouTube (:20)  also also known as London Dispersion Forces  even nonpolar molecules have forces that hold them together  the distribution of electrons around an individual atom, at a given instant in time, may not be perfectly symmetrical › this can produce a temporary, instantaneous dipoles (polar molecule) › this can then induce a nearby molecule to be polar and therefore a very weak attraction between the two molecules  and so on, and so on…

11. Sticky secret. Tiny hairs on geckos' feet help maximize contact with surfaces, allowing van der Waals forces to go to work.

12.  attractive forces between the positive end of one polar molecule and the negative end of another polar molecule  must be in close proximity for the dipole- dipole forces to be significant  stronger than van der Waal's forces

14.  YouTube Hydrogen Bonding (1:40) YouTube Hydrogen Bonding (1:40)  YouTube Hydrogen Bonding Video (:58) YouTube Hydrogen Bonding Video (:58)  a specific type of dipole-dipole type interactions  stronger than other dipole-dipole and/or dispersion forces  the hydrogen in a molecule (e.g. H-F, H-O or H-N) is bonded to a small, highly electronegative element (usually an F, O or N atom) on another molecule