How are Molecules Depicted? 6.2

Lewis Structures Valence e- = an e- in the outermost E level of an atom and determines the chemical properties Lewis Structure = a structure in which e- are represented by dots: dot pairs or dashes b/t 2 atomic symbols represents pairs in covalent bonds

Lewis Structure Single Bond = covalent bond in which one pair of e-’s are shared b/t 2 atoms Unshared pairs = a nonbonding pair of valence e- not involved in bonding to another atom

Simple Lewis Structures Draw the Lewis structures for the following elements… K, Sr, Al, Kr, P, O Remember e- want to be as far apart as possible

How to draw LS for more complex molecules 1.Draw the LS for each element 2.Put least electronegative element in center 3.Arrange other elements around central atom to satisfy octet (H only needs 2) 4.Change dots to lines to show bonds b/t atoms

Practice Try drawing the Lewis structures for… NH 3 CH 4 H 2 OCH 2 F 2 Worksheet on Lewis Structures! F2O2F2O2F2O2F2O2 N2C2H4N2C2H4N2C2H4N2C2H4

Multiple Bonds Used when single bonds don’t satisfy octets for each atom Resonance structure – a possible Lewis structure of a molecule when more than 1 L.S. is possible Delocalized – e- shared b/t more than 2 atoms

Practice CaKBr CO 2 HCN Lewis Structures with Ions! NH 4 + CN - CO 3 2- OH -

Naming Covalent Compounds Inorganic molecular compounds Specify # of each type of atom P 4 O 6 – Tetraphosphorus hexoxide P 4 O 10 – Tetraphosphorus decoxide

Mono1 Di2 Tri3 Tetra4 Penta5 Hexa6 Hepta7 Octa8 Nona9 Deca10 Covalent prefixesCovalent prefixesCovalent prefixesCovalent prefixes

Naming Covalent Compounds If there is 1 of the first element, mono is omitted from the word CO – carbon monoxide CO 2 – carbon dioxide

Naming Covalent Compounds 1 st element – named 1 st – usually least e-neg 2 nd element – named 2 nd – usually most e-neg – add ide ending Drop vowels o and a from prefix before adding it to a root that starts with a vowel

Naming Covalent Compounds N 2 O 4 – Dinitrogen tetroxide SF 6 – Sulfur hexafluoride Some common names are used instead of technical name H 2 O – water – not dihydrogen monoxide