2. Binary Covalent Compounds Two elements (not necessarily 2 atoms) Two nonmetals

3. Two naming systems Stock system – like we learned for ionic compounds, “official” Traditional – what you hear on the news.

4. Both Traditional & Stock LessLess electronegative of the two elements is first. REM: you can look up electronegativities in table S.

5. Electronegativity Ability of an atom to attract electrons in a chemical bond.

6. Stock System for Covalent Cmpds mustFirst element must have Roman Numeral after it. Have to figure out its oxidation number.

7. Stock System & Oxidation Number NOTMolecular substances do NOT contain ions, but we use the concept of oxidation number for electron bookkeeping. The oxidation number is the charge an atom would have, if we pretend all its bonds are ionic. PRETEND all shared electrons go to the atom with higher electronegativity.

8. 7 Rules for Oxidation Numbers of a free, uncombined element = 0. Na He O 2 N 2 S 8 Cl 2 P of a monatomic ion = charge on ion. 2. Fluorine is always -1. 3. 1. Ca +2 = +2. Cl -1 = -1. Al +3 = +3. CF 4

9. 7 Rules for Oxidation Numbers Oxygen is nearly always -2 except when its Hydrogen is nearly always +1, except when it’s bonded to a metal. Then it’s -1.4. 5. LiH CaH 2 NaH OF 2 O 2 2- -Bonded to fluorine, where O is +2 -In the peroxide ion, where O is -1.

10. 7 Rules for Oxidation Numbers The sum of oxidation numbers in a neutral compound is 0. The sum of oxidation numbers in a polyatomic ion = charge of the ion. 6. 7. H 2 O CO 2 NO SO 3 Sum in SO 4 2- = -2. Sum in NO 3 - = -1.

11. Naming Binary Covalent Compounds With The Stock System

12. CO 2 less CO 2 : C goes first because it’s less electronegative than O. CO 2 Each O is -2. Total = -4. Total = +4. Each C is +4. Carbon (IV) oxide

13. Try SO 3 SO 3 Each O is -2. Total “neg” = -6. Total “pos” = +6. Each S is +6. Sulfur (VI) Oxide

14. Try N 2 O 3 N2O3N2O3N2O3N2O3 Each O is -2. Total “neg” = -6. Total “pos” = +6. Each N is +3. Nitrogen (III) oxide.

15. Try P 2 O 5 P2O5P2O5P2O5P2O5 Each O is -2. Total “neg” = -10. Total “pos” = +10. Each P is +5. Phosphorus (V) oxide

16. Stock System Names CO NO NO 2 NO 3 N 2 O 5 PCl 3 SiH 4 Carbon (II) oxide Nitrogen (II) oxide Nitrogen (IV) oxide Nitrogen (VI) oxide Nitrogen (V) oxide Phosphorus (III) chloride Silicon (IV) hydride

17. Naming Binary Covalent Compounds With The Traditional Naming System

18. Traditional Naming Less electronegative element is named 1 st. stemGive stem of 2 nd element plus “-ide” ending. Use prefixes to tell how many of each element. –Except NEVER start a name with “mono-”

19. Prefixes: Traditional System # of AtomsPrefix# of AtomsPrefix 1Mono6Hexa 2Di7Hepta 3Tri8Octa 4Tetra9Nona 5Penta10Deca

20. Stems: just a reminder H = hydrC = carbN = nitrO = oxF = fluor Si = silicP = phosph S = sulfCl = chlor As = arsen Se = selen Br = brom Te = tellur I = iod

21. Traditional Naming H2OH2O NH 3 N2H4N2H4 NO NO 2 N2ON2O Dihydrogen monoxide Nitrogen trihydride Dinitrogen tetrahydride Nitrogen monoxide Nitrogen dioxide Dinitrogen monoxide