Naming & Calculating Chemical Compounds

1. Naming & Calculating Chemical Compounds Unit3 – Lecture 8

2. Recap – Bonding Occurs… • …to fill the outer level of electrons of elements • you can predict bonding by observing trends on the periodic table: • type of element: metals, non metals, etc • valence electrons: for lewis diagrams • oxidation #: criss-cross method

3. Counting Atoms • Chemical Formula - shows how many of which atoms are in a molecule • Coefficient - placed in front of a molecule to show more than one molecule • Subscript - number placed below and behind a symbol to show how many of which atoms are present 3H2O

4. Counting Atoms • Diatomic Molecule - two atoms of the same nonmetal (usually in gas form) that have bonded together • Reactive nonmetals will bond with one another if no other substance is available for bonding H2 N2 O2 F2 I2 Cl2 Br2

5. Polyatomic Ions • a group of atoms that behave as one atom • keep together as a unit • if more than one polyatomic ion is present in a molecule, parentheses set it apart • Still use a subscript to show how many • How many (OH)? Ca(OH)2 NH4Cl

6. Common Polyatomic Ions • See your packet…

7. How Many? • Making formulae – the “Criss Cross” Method background: • uses oxidation numbers to predict # of each element in a compound when 2 elements bond • Oxidation # Review: • + or – sign, indicates # of electrons that will be gained or lost • written like a charge in the upper right • always included [given to you] if you have polyatomic ions

8. Oxidation/Charge Numbers +1 +2 ----------------------------------------- +3 +/-4 -3 -2 -1 0

9. Oxidation #s – cont’d • Transition metals have more than one oxidation number!!!! • Fe[III] = Fe+3 = Iron with +3 oxidation number • Fe[II] = Fe+2 = Iron with +2 oxidation number • Mn[II] = Mn+2 = Manganese with +2 oxidation number • Mn[III] = Mn+3 = Manganese with +3 oxidation number

10. Making Formulae – the “Criss-Cross” Method • cation first – write element & oxidation # • anion next – write element & oxidation # • without the + or – sign • write the oxidation # from one symbolon the other as a subscript • remember to add parentheses aroundpolyatomic ions • don’t write the #1, it is implied • reduce any evenly-divisible subscripts

11. Examples • Bond btw Aluminum and Oxygen • Bond btw Aluminum and Carbonate [CO3]-2

12. Examples • Bond btw Aluminum and Oxygen • Al +3 O -2 • Al2O3 • Bond btw Magnesium and Borate[BO3]-3 • Mg +2 (BO3) -3 • Al3(BO3)2

13. Practice Complete practice problems 1-9 in your packet.

14. Reverse Criss-Cross • use to find oxidation on atoms in a compound. • PCl3  P Cl3  So… P is 3, and Cl is 1 • for transition metals – VERY useful • Ti Cl2  Ti Cl2  So… Ti is 2 and Cl is 1 • Oxidation for Ti is +2 

15. Binomial Nomenclature • a “two name” “naming” system • like Genus species from biology…. • Used to differentiate between elements and compounds • Fluorine (an element) vs Fluoride (part of a compound) • Never change the name of a Polyatomic Ion • Big difference between Sulfide, Sulfite, and Sulfate

16. Naming Ionic Compounds • List the positive ion (or metal) first • ***Use Roman Numerals to show the Oxidation number of a transition metal • Name the negative ion (or nonmetal), changing the ending to –ide • “Oxide” • “Sulfide” • “Phosphide” • Ex: FeO / Fe2O3 • = Iron II Oxide / Iron III Oxide

17. Practice • Complete practice – Naming Ionic Cmpds page 14

18. Naming Polyatomic Compounds • cmpd is polyatomic if there are more than 2 elements You will be given the names for common polyatomics. Still only 2 words in the name • first term = positive ion name • second term = negative ion name • if second term is NOT a polyatomic, change ending to -ide • if the second term is a negative polyatomic, do NOT change the ending

19. Practice • complete the practice problems 1-3.

20. Homework • finish any practice problems from lecture • complete Naming IONIC Compounds w/s [1-14] ONLY HONORS ONLY: • make 2 sets of polyatomic ion cards [for the ten given] • name  formula [should still include charge…] • name  charge

21. Naming Covalent Compounds • Prefixes are used to show how many of which atoms • = number terms from Greek / Latin • Write the name of the cation [or most positive] • only add a prefix for the first atom if there is more than one • Write the name of the anion [or most negative] • add a prefix to tell how many are present • change the ending to -ide

22. Numbering Prefixes 1 – Mono- 2 – Di- 3 – Tri- 4 – Tetra- 5 – Penta- 6 – Hexa- 7 – Hepta- 8 – Octa- 9 – Nona- 10 – Deka-

23. Practice • What is the name for N2O4? • non-metal + non-metal…so covalent • Dinitrogen Tetraoxide • What is the name for Na2S? • metal + non-metal = ionic • Sodium Sulfide • What is the name for CO2? • non-metal + non-metal = covalent • Carbon Dioxide

24. Practice – cont’d • What is the name for (NH4)2O?[hint: you need to know what (NH4) is…] • Nitrogen Hydrogen Oxide • Mononitrogen Tetrahydrogen Oxide • Ammonium Oxide • Diammonium Oxide • Ammonium Oxalate CORRECT!!!!

25. Practice – cont’d Al2S3 CrO Lead (II) oxide PbO2 (NH4)2S Ca(OH)2 Iron (II) cyanide Fe(NO3)3 Aluminum sulfide Chromium (II) oxide PbO Lead (IV) oxide Ammonium sulfide Calcium hydroxide Fe(CN)2 Iron (III) nitrate