1. October 6, 2015October 6, 2015October 6, 2015 GSCI 163 Spring 2010 material  Electron configuration  Bonding IonicIonic CovalentCovalent MetallicMetallic Hydrogen (next)Hydrogen (next)  Apply Lewis diagram to get chemical formulas (at least a good guess- some formulas are exceptions to rules)

2. October 6, 2015October 6, 2015October 6, 2015 GSCI 163 Spring 2010 Lewis Rules   Arrange the atoms (central atom lowest electornegativity)   Count up total valence electronsDraw single bonds between central atom and surrounding atoms   Place remaining electrons, in pairs, around appropriate atoms; start with outer atoms.   Make sure all atoms that need octets have octets

3. October 6, 2015October 6, 2015October 6, 2015 GSCI 163 Spring 2010 Example nitrite ion is NO2− nitrite  Nitrogen is the least electronegative atom, so it is the central atom by multiple criteria.  Nitrogen has 5 valence electrons; each oxygen has 6, for a total of (6 × 2) + 5 = 17. The ion has a charge of −1, which indicates an extra electron, so the total number of electrons is 18.  Each oxygen must be bonded to the nitrogen, which uses four electrons — two in each bond. The 14 remaining electrons should initially be placed as 7 lone pairs. Each oxygen may take a maximum of 3 lone pairs, giving each oxygen 8 electrons including the bonding pair. The seventh lone pair must be placed on the nitrogen atom.  Both oxygen atoms currently have 8 electrons assigned to them. The nitrogen atom has only 6 electrons assigned to it. One of the lone pairs on an oxygen atom must form a double bond, but either atom will work equally well. We therefore must have a resonance structure.  Two Lewis structures must be drawn: one with each oxygen atom double-bonded to the nitrogen atom. The second oxygen atom in each structure will be single-bonded to the nitrogen atom. Place brackets around each structure, and add the charge (−) to the upper right outside the brackets. Draw a double-headed arrow between the two resonance forms. O6N5 charge total18

4. October 6, 2015October 6, 2015October 6, 2015 GSCI 163 Spring 2010 For ionic bonds sometimes the elctron is shown as completely transferred and the ion charges shown.

5. October 6, 2015October 6, 2015October 6, 2015 GSCI 163 Spring 2010 Reactions  Oxidation (burn) H2+O2  H2O unbalancedH2+O2  H2O unbalanced H2+O2  2H2OH2+O2  2H2O 2H2+O2  2H2O2H2+O2  2H2O  2 moles of hydrogen gas (diatomic) and one mole of oxygen gas (diatomic) reacts to create two moles of water.

6. October 6, 2015October 6, 2015October 6, 2015 GSCI 163 Spring 2010