1. Breakdown of Topics I.Chemical formulas, Relation to Type of Substances, “Formula Unit” concept, and Visual connections (related to Tro, 3.3, 3.4) II.Ionic Compound Formulas A.Difference between ions and ionic compounds (formula writing) B.The “neutrality principle” concept III.Naming of Compounds (not elements!) A.Ionic Compounds B.Binary Molecular Compounds C.Acids 1

2. I. Chemical Formulas Revisited Related to “nanoscopic pictures” –Every substance is composed of “basic units” –If sample A has “more of” a substance than sample B, it has more “basic units” of that substance: Sample A of NO 2 Sample B of NO 2 Every substance has a single chemical formula that represents its “basic unit” One “unit” of any substance can be called a “formula unit”! (Here, one molecule = 1 formula unit) 2

3. Reminder MonatomicMolecular Ionic Each of these has a chemical formula… …these do not have a chemical formula Note: there are four kinds of substances… …and their formulas “tell you” which is which!... How many substances are in the box? How many chemical formulas would be needed to describe the matter in the box? 3 Quick quiz: Ans. 2 (e.g., CS 2 & O 3 )

4. Fig. 3.4 Four types of substances—relationship to nanoscopic entities & chemical formulae Look closely at the different formulas—can tell the difference between an element and a compound? A monatomic vs polyatomic element? 4

5. How do you recognize a monatomic element from a formula? single element symbol with no subscript –Fe, Co, He Fe (s) He (g) Chemical formula State designation One “unit” of the substance. The chemical formula represents one unit of a substance. Unit = atom 5

6. How do you recognize a molecular element from a formula? A single element symbol with a subscript –S 8, N 2, P 4, C 60 C 60 (s) H 2 (g) Chemical formula C 60 Image: courtesy of J. Lauher's Fullerene Structure LibraryFullerene Structure Library One “unit” of the substance. The chemical formula represents one unit of a substance. Unit = molecule 6

7. How do you recognize a molecular compound from a formula? more than one element symbol (  compound) first one is NOT that of a metallic element (exception later) (  molecular) –CH 4, SO 2, SO 3, P 4 O 10 CH 4 (s) SO 3 (g) Chemical formula One “unit” of the substance. The chemical formula represents one unit of a substance. Unit = molecule 7

8. How do you recognize an ionic compound from a formula? more than one element symbol (  compound) first one IS that of a metal (exceptions later) (  ionic) –NaCl, FeCl 3, CuSO 4, Na 3 PO 4 NaCl (s) FeCl 3 (s) Chemical formula The chemical formula still represents one unit of a substance, but it is not a separate grouping as in molecular substances. Basic units are “ions”… …but THE “unit” is a specific grouping of ions (indicated by the formula) …what do you call “it” (the “unit”)? …a “formula unit”! 8

9. Formula units (FU) are the “basic units” of ionic compounds A formula unit is an amount of a substance. You can have: −one FU of NaCl or −Two FU of NaCl or −25,333 FU of NaCl or −1.56 x 10 21 FU of NaCl Just like you can have: −one molecule of CO 2 or −Two molecules of CO 2 or −25,333 molecules of CO 2 or −1.56 x 10 21 molecules of CO 2 Quick Quiz: Can you have: 4.3 FU of NaCl? 0.5 FU of CO 2 ? NO! A FU is a “unit” of a substance—you cannot have a “fraction” of one! You can only have a whole number of them. 9

10. Formula Unit is just another term for “basic unit” of any substance Most chemists use the term “formula unit” only with ionic compounds (b/c you can use “atom” or “molecule” for the other kinds of substances) However, I often use the term with monatomic elements or molecular substances as well − e.g., 15 FU of CO 2 means 15 molecules of CO 2 − e.g., 432 FU of Fe means 432 atoms of Fe “More” of a substance means more “formula units” of it! 10

11. How many FUs of each substance are present? 7685 7124 ___ FU of Fe ___ FU of He ___ FU of CH 4 ___ FU of SO 3 ___ FU of N 2 ___ FU of NaCl___ FU of FeCl 3 11

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13. II. Ion and Ionic Compound Formulas The chemical formula of any ion MUST show the charge as a superscript on the right: –Na +, Ru 3+, Ca 2+, O 2-, NO 2 -, PO 4 3- The chemical formula of any ionic compound MUST show NO CHARGES AT ALL! –Na 2 O, Ru 2 O 3, Ca(NO 2 ) 2, Na 3 PO 4 NOTE: Your only clue that a compound formula represents an ionic compound is noticing the metal in front (exception later) 13

14. Subscripts of ions tell you how many (of each) are in 1 FU Formula Na 2 O Ru 2 O 3 Ca(NO 2 ) 2 Na 3 PO 4 1 FU contains exactly: Two Na + ions and one O 2- ion Two Ru 3+ ions and three O 2- ions One Ca 2+ ion and two NO 2 - ions Three Na + ions and one PO 4 3- ion NOTE: Parentheses are used ONLY if more than one of a polyatomic ion is present in one FU. 14

15. What determines the number of each ion in a formula unit of an ionic compound? The charges on the cation and anion that make it up! The oppositely charged ions will come together in the ratio that makes each formula unit electrically neutral –“neutrality principle” 15

16. Neutrality Principle A formula unit is always NEUTRAL overall  The grouping of cations and anions must be neutral overall! Total positive charge = total negative charge Formula Na 2 O: Na + Na + O 2-  +1 + (+1) + (-2) = 0 Na 3 PO 4 Na + Na + Na + PO 4 3-  3(+1) + 1(-3) = 0 16

17. Test: Use Neutrality Principle to Determine the Charge on an Ion Assume you know that O forms 2- ions (i.e. “O” = O 2- ) What is the charge on the Ru ions in Ru 2 O 3 ? ANS: +3 3 x 2- = -6 for the three O 2- ions.  The two Ru ions must add up to +6 2 x ___ = +6 +3 charge per ion 17 Ru ? O 2- 1 FU of compound; net charge must be zero

18. Test: Use Neutrality Principle to Determine the Charge on an Ion What is the charge on the Pb ions in PbO 2 ? ANS: +4 2 x 2- = -4 for the two O 2- ions. The one Pb ion must add up to +4 **If you said +2 then you are using a shortcut instead of thinking about the MEANING of the subscripts! They are NOT “charges”—they represent the number of ions in 1 FU** 18 Pb ? O 2- 1 FU of compound; net charge must be zero

19. Use the neutrality principle to determine the formula for an ionic compound Ions Fe 3+ & Br - Ti 4+ & S 2- Ca 2+ & PO 4 3- NH 4 + & SO 4 2- Formula: FeBr 3 TiS 2 Ca 3 (PO 4 ) 2 (NH 4 ) 2 SO 4 Why do you need this skill? To determine the chemical formula from the name! “Cobalt(III) carbonate” is composed of cobalt(III) ions (Co 3+ ) and carbonate ions (CO 3 2- ): Formula is: _________ 19 Co 2 (CO 3 ) 3

20. III.A Naming Ionic Compounds Cation Name + Anion Name That’s it!!! Hard part: names of the ions! 20

21. Na + Li + K+K+ Rb + Cs + Be 2+ Mg 2+ Ca 2+ Sr 2+ Ba 2+ Al 3+ Zn 2+ Ag + Ra 2+ Cations that always have the same charge (can memorize) 2) One Polyatomic cation: NH 4 +, ammonium ion 21 Fr + 1) Monatomic, Type I cations (in this class)

22. Cations with more than one possible charge (Type II) need a Roman Numeral Any metal cation other than those on previous slide! –Any transition metal ion other than Ag + or Zn 2+ –Any metal ion directly under the staircase other than Al 3+ Must use neutrality principle to figure out the charge (if not given to you)! Write the charge as a Roman numeral in parentheses 22

23. Type II Cation Examples Fe 3+ is iron(III) ion; Fe 2+ is iron(II) Pb 4+ is lead(IV) ion; Pb 2+ is lead(II) Cu + is copper(I) ion; Cu 2+ is copper(II) Cr 6+ is chromium(VI) ion; Cr 3+ is chromium(III) But: Ag + is just silver ion (Type I) Zn 2+ is just zinc ion (Type I) 23

24. Anions—Preliminary Comment It will be much easier to learn anion names if you know these nonmetal elements’ symbols and names (next slide). 24

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26. Anions—Three Endings (-ide, -ate, and –ite) -ides 1)Monatomic Use Periodic Table: 26 2)Two polyatomic ones to memorize CN - (cyanide); OH - (hydroxide) P 3- Phosphide

27. Anions (continued) -ates –Polyatomic, contain oxygen (“oxoanions”) –Learn the four “core ions” first (next slide) Then others from them… 27

28. Some “–ate” ions to learn first… NO 3 - nitrate SO 4 2- sulfate PO 4 3- phosphate CO 3 2- carbonate …and second (analogous to nitrate) : ClO 3 - chlorate BrO 3 - bromate IO 3 - iodate 28

29. Mnemonic-- “Poconoso” 29 PO CO NO SO 3 2 1 2 PO 4 3- CO 3 2- NO 3 - SO 4 2- 4 3 3 4 charge (negative) # oxygen atoms

30. “Hydrogen ___” ions come from adding H + to an oxoanion 30

31. What’s the name of HS - ion? Ans: hydrogen sulfide (not on sheet!) 31

32. Anions (continued) -ites –One less oxygen than “ate” counterpart –Sulfate → sulfite (SO 4 2- → SO 3 2- ) 32

33. “-ites” come from “-ates”! 33

34. “Per-” and “Hypo” in sets of four ClO 4 - perchlorate (from “hyper”) ClO - hypochlorite (from “hypo”) ClO 3 - chlorate ClO 2 - chlorite Summary: Prefixes of “per” (4 O’s) and “hypo” (1 O) are added in cases where there are four “versions” instead of two. 34

35. A few additional anions don’t follow any obvious pattern (memorize) MnO 4 - permanganate (analogous to ClO 4 - ) C 2 H 3 O 2 - acetate CrO 4 2- chromate Cr 2 O 7 2- dichromate 35

36. Examples!!! See handout (and board for detailed solutions to Q’s below): BaCO 3 Fe(NO 3 ) 2 PbCl 4 AgClO barium carbonate iron(II) nitrate lead(IV) chloride silver hypochlorite iron(II) hydroxide _________________ magnesium phosphite _____________ Fe(OH) 2 Mg 3 (PO 3 ) 2 36

37. IIIB. Naming Binary Molecular Compounds “binary”-two different kinds of atoms (2 different elements’ symbols in formula) “molecular”- basic units are molecules –Molecules are made of atoms –Atoms are neutral –What’s the ratio of atoms in a molecule? NO SINGLE “ANSWER” It varies! (no “neutrality” principle to “restrict” b/c atoms already neutral!) CO and CO 2 ; NO, N 2 O, NO 2,, N 2 O 4, etc. all exist! –Later, we’ll explore models of bonding… 37

38. Naming Binary Molecular Compounds (continued) Thus, prefixes are needed to let the reader know what that ratio (and exact composition of a FU) is! –Note: NO 2 and N 2 O 4 mean different things even though ratio is the same! General “Recipe” for name: –1 st Element Name + 2 nd element’s stem + -ide –Add prefixes as needed to the element or element stem NOTE: “Mono” is left off 1 st Element Name 38

39. Examples N 2 O: dinitrogen monoxide NO 2 : nitrogen dioxide NO: nitrogen monoxide N 2 O 4 : dinitrogen tetroxide P 4 O 10 : tetraphosphorus decoxide CF 4 : carbon tetrafluoride SCl 6 : sulfur hexachloride http://www.youtube.com/w atch?v=NJn76CR70oU (start at 3:20)http://www.youtube.com/w atch?v=NJn76CR70oU 39

40. The Prefixes You Need to Know 1: mono (only used on second element) 2: di 3: tri 4: tetra 5: penta 6: hexa 7: hepta 8: octa 9: nona 10: deca 40

41. Comment Do not confuse the –ide ending with the “ides” of actual anions!!!!! There are NO IONS in binary molecular compounds, even though the “ide” may make it sound as such! –CCl 4, carbon tetrachloride does NOT contain any chloride ions. –I wish that the naming system were completely different for molecular compounds (no “–ides”), but I don’t get to decide! http://www.youtube.com/watch?v=NJn76CR70oU (start at 3:20)http://www.youtube.com/watch?v=NJn76CR70oU 41

42. Examples Sulfur trioxide __________________ B 2 F 6 __________________________ SrF 2 __________________________ SO 3 diboron hexafluoride strontium fluoride (no “di” here!**) ** The last one is ionic, not molecular! Make sure to identify “ionic” vs. “molecular” before you begin to name a substance!! 42

43. IIIC. Acids—A subset of molecular compounds Molecular compounds that yield ions when dissolved in water!? (more later) Always have H written first Imagine making any acid by adding H + ‘s to any anion in order to make a neutral formula unit. The ENDING of the anion determines the name of the acid: –Ide → hydro ___ic acid –Ate → ____ic acid –Ite → ____ous acid http://www.youtube.com/watch? v=a5nC2evhUa0http://www.youtube.com/watch? v=a5nC2evhUa0 http://www.youtube.com/watch? v=LoSLKUN7FQ4 (start at 1:35)http://www.youtube.com/watch? v=LoSLKUN7FQ4 43

44. Examples Hydrosulfuric acid _________________ Sulfuric acid ______________________ Chloric acid _______________________ Hypochlorous acid _________________ H 3 PO 3 __________________________ HNO 3 ___________________________ HNO 2 ___________________________ HCN ____________________________ H2SH2S H 2 SO 4 HClO 3 HClO phosphorous acid nitric acid nitrous acid hydrocyanic acid 44

45. From Practice Handout *You don’t need to memorize oxalate 45

46. For some web practice http://www.stolaf.edu/depts/chemistry/cour ses/toolkits/125/js/naming/http://www.stolaf.edu/depts/chemistry/cour ses/toolkits/125/js/naming/ http://web.mst.edu/~gbert/names/Aionic.H TML –NOTE: This site does NOT do Type II metals at all! 46