1. What are Covalent Compounds? A combination of two or more non- metal atoms that share electrons in a bond. Also called a molecule

2. Properties of Covalent Compounds: They can be solid, liquid, or gas They are not good conductors of electricity. Some may dissolve, like sugar. However most do not dissolve, like SiO 2 –Why might some covalent compounds form solids or liquids or gasses

3. What does sharing valence electrons look like? It is best to draw a model –Specifically a Lewis Model We combine Lewis structures so every atom has 8 electrons (Hydrogen always needs 2). Covalent compounds form so every nonmetal has a full valence shell.

4. Examples

5. How to draw a model: Let’s use H 2 O as a model 1.Determine the Type of Atoms and the number of atoms in the formula H (x2) O (x1)

6. How to draw a model: Draw the Lewis structure for each atom. This Helps you determine the number of valence electrons for each atom.

7. How to draw a model: Determine the number of total valence electrons for the molecule (covalent compound) This will give us the number of electron pairs by dividing the total number of electrons by 2. It is important to use pairs because electrons always pair up in covalent compounds

8. How to draw a model: 2 e - 6 e - Total electrons = 8 e - Total number of pairs (8 e - )/2 = 4 pairs

9. How to draw a model: Arrange the atoms in a structure that has the lone atom in the middle and the additional atoms surrounding that atom H O H If carbon is present it is always in the middle If Hydrogen is present it is never in the middle.

10. How to draw a model: Connect the Atoms by electron pair bonds Bonding pairs Now add the additional pairs (lone pairs) so all atoms have 8 e - (H has 2 e - ) Lone Pairs

11. How to draw a model Finally count the number of electrons in the model. – Be sure that the number of pairs used equals the number of pairs calculated –Note: Sometimes you may need to double or triple bond atoms. – O 2 N 2

12. Naming Covalent Compounds There are many ways to name covalent compounds. We will go over several rules. However you will need to memorize the formulas and names of the following: 1.Prefixes 2.Diatomic Elements 3.Acids and Bases 4.Hydrocarbons Extra Credit for flash cards on Wednesday.

13. Block to do list: 1.Staple all stamp sheets to the front of your group lab and turn them in 2.On a separate sheet of paper answer the following: –Name: O 2, H 3 PO 4, C 4 H 10, P 2 H 6 –Write the formula: Nonane, Acetic Acid, Fluorine, Silicon tetraiodide –Draw the lewis structure for Silicon tetraiodide or C 2 I 2.

14. Naming Covalent Compounds There are many ways to name covalent compounds. We will go over several rules. However you will need to memorize the following: 1.Prefixes 2.Diatomic Elements 3.Acids and Bases 4.Hydrocarbons

15. Naming Covalent Compounds 1.There are many compounds that are covalent. We need to memorize the names of acids, bases, organic compounds, and diatomic elements because they do not have specific rules for naming 2.However, many inorganic compounds do follow specific rules for naming

16. Naming Covalent Compounds Example: CO 2 1.The name of the first element is written unchanged. (Carbon) –You must add a prefix if there is more than one element. ( ex. C 2 would be dicarbon) –The second element is a combination of a prefix, the root name of the element, and the ending –ide. (Di ox ide…Dioxide) Carbon Dioxide

17. Naming Covalent Compounds 3.The o or a at the end of the prefix is usually dropped when the word following the prefix begins with a vowel. –Example CO is Carbon Monoxide. Not Carbon Monooxide

18. Naming Covalent Compounds Let’s name the following: S 2 Cl 2 CS 2 SO P 4 O 10 Si 2 I 6

19. Naming Covalent Compounds Let’s name the following: S 2 Cl 2 Disulfur Dichloride CS 2 Carbon Disulfide SOSulfur Monoxide P 4 O 10 Tetraphosphorus Decoxide Si 2 I 6 Disilicon Hexiodide

20. Naming Prefixes Mono 1 Di 2 Tri 3 Tetra 4 Penta 5 Hexa 6 Hepta 7 Octa 8 Nona 9 Deca 10

21. Hydrocarbons Methane CH 4 Ethane C 2 H 6 Propane C 3 H 8 Butane C 4 H 10 Pentane C 5 H 12 Hexane C 6 H 14 Heptane C 7 H 16 Octane C 8 H 18 Nonane C 9 H 20 Decane C 10 H 22

22. Diatomic Elements: Dr. BrINClHOF Bromine Br 2 Iodine I 2 NitrogenN 2 ChlorineCl 2 HydrogenH 2 OxygenO 2 FluorineF 2

23. Acid and Base Names HClHydrochloric Acid H 2 SO 4 Sulfuric Acid H 3 PO 4 Phosphoric Acid HC 2 H 3 O 2 Acetic Acid HNO 3 Nitric Acid NH 3 Ammonia (Base) KOH Potassium Hydroxide(Base) NaOH Sodium Hydroxide (Base)

25. Physical Properties of Covalent Compounds Why are some covalent compounds: –Gasses (like O 2 ) –Liquids (like H 2 O) –Solids (like sugar C 6 H 12 O 6 ) Why are all ionic compounds solid? There is no clear distinction between ionic and covalent…

26. So how do we determine the physical behavior of a compound? Electronegativity: This is the measure of the ability of an atom in a bond to attract electrons to itself.Electronegativity Equal Electronegativity Different electronegativity e- equally sharede- not equally shared

28. Electronegativity is a periodic Trend Fluorine has the greatest electronegativity Cesium has the lowest electronegativity Noble gases have no electronegativity because they do not bond

29. Electronegativity Which atom has greater electronegativity?

30. Electronegativity Scale We can determine the type of bond by the following scale of the ∆EN (difference in electronegativity) between atoms 1.Ionic Bonding: unequal sharing ∆EN greater than 1.7 2.Polar covalent Bonding: somewhat unequal ∆EN= 1.7 to 0.4 3.Covalent Bonding: Equal sharing ∆EN= less than 0.4

31. Determine the type of Bond O 2 H 2 O NaF CH 4

32. NaCl Dissolves 5 Chemical Reactions