2. Molecular Compounds  A pure substance formed from two or more non-metals  Forms a molecule in contrast to a crystal of ions like in an ionic compound  Majority of known compounds are molecular Ex: water H 2 O sugar C 12 H 22 O 11 carbon dioxide CO 2

3. N 2 O VS NO 2  N 2 O, nitrous oxide, colourless sweet- smelling gas used to relax nervous patients  NO 2 nitrogen dioxide, reddish-brown toxic gas produced in the atmosphere from pollutants emitted from automobile exhaust. (catalytic converter prevents this)

4. Covalent Bonding  occurs between 2 non metals  Both non metals have a strong attraction to their electrons and will NOT give them up.  Therefore atoms share electrons— similar to a “tug of war”

5.  Molecules of 2 atoms joined with a covalent bond are called diatomic molecules  Covalent bonds can form between 2 identical atoms or 2 different ones Ex: 2 hydrogen atoms H 2  The covalent bond is represented by a solid line Ex: H-H

7.  Sometimes diatomic molecules share 2 pairs of electrons Ex: Oxygen ( O 2 ) O  These double covalent bonds are shown as 2 solid lines

8.  Other diatomic molecules are made up of 2 different elements Ex:hydrogen fluoride HF

9.  Sometimes there are 3 or more atoms making up a molecule Ex:water H 2 O 1 oxygen and 2 hydrogen

10. Common elements that exist as diatomic molecules NAME OF ELEMENTCHEMICAL SYMBOL FORMULA OF MOLECULE STATE AT ROOM TEMP. HydrogenHH2H2 Gas OxygenOO2O2 Gas FluorineFF2F2 Gas BromineBrBr 2 Liquid IodineII2I2 Solid NitrogenNN2N2 Gas ChlorineClCl 2 Gas

11. Naming Molecular Compounds  Different than naming ionic compounds  Some use common names from centuries ago Ex:ammonia  NH 3 nitric oxide  NO hydrogen sulfide  H 2 S

12.  Chemists use prefixes to specify the number of atoms in a molecular compound Exdinitrogen pentoxide 2 nitrogen 5 oxygen N 2 O 5 Ex:carbon dioxide 1 carbon2 oxygen CO 2

13.  The prefix mono means one Ex:carbon monoxide 1 carbon 1 oxygen CO

14. Prefixes for Molecular Compounds PREFIXNUMBER OF ATOMSSAMPLE MOLECULAR COMPOUND mon(o)1carbon monoxide CO di2carbon dioxide CO 2 tri3sulfur trioxide SO 3 tetra4carbon tetrachloride CCl penta5phosphorous pentafluoride PF 5

15.  1 st check to see that the compound contains a metal—if it does, it’s an ionic compound!  If compound contains 2 non-metals perform the following steps Ex PCl 3 1Write the names of both elements in the same order as the formula phosphorous chlorine 2Replace the 2 nd element with the “ide” ending phosphorous chloride 3Add prefixes, (remember “mono” is never used for the first element phosphorous trichloride Steps in Naming :

16. What about N 2 O? 1 nitrogen oxygen 2 nitrogen oxide 3 dinitrogen monoxide

17. Molecular Compounds Writing Their Chemical Formulas  The prefixes in the name of a molecular compound become the subscripts in the formula Ex:sulfur dioxide is SO 2

18. Homework  Pg 212 # 3, 5, 6, 7(read pg 210), 9, 10  Work Sheet