2. Molecular Compounds  Consists of two or more non-metals  Majority of known compounds are molecular Ex: water H 2 O sugar C 12 H 22 O 11 carbon dioxide CO 2

3. Covalent Bonding how molecular compounds are formed  occurs between 2 non metals  Non metals don’t like to give up their electrons  Therefore atoms share electrons— similar to a “tug of war”

4.  diatomic molecules are molecules with two atoms  can form between 2 identical atoms Ex: 2 hydrogen atoms H 2  Other diatomic molecules are made up of 2 different elements  The covalent bond is represented by a solid line Ex: H-H

5. Ex: hydrogen gas H 2

6. Ex:hydrogen fluoride HF

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

9. 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

10.  Prefixes are used 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 Naming Molecular Compounds

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

12. 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

13.  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 Example 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 :

14. Try N 2 O? 1 nitrogen oxygen 2 nitrogen oxide 3 dinitrogen oxide

15. 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