1. Chem 11 Exam 3 Review November 13, 2006,

2. Exam Topics Naming compounds Writing formulas Ion names and charges Balancing equations Recognize ionic and covalent Use Lewis structures to get bonds and lone pairs Electronegativity Isoelectronic/Identical to

3. Nomenclature Terms  Binary Compound : contains 2 elements  Binary Ionic Compound : a metal and a nonmetal -> metal named first If metal has more than one charge must indicate charge with (Roman numerals) or Latin endings -ous = lower charge - ic = higher charge

4. Nomenclature Terms Binary Covalent Compound: two nonmetals Least electronegative element named first Second element has -ide ending Greek prefixes indicate subscripts 1 = mono-6 = hexa- 2 = di-7 = hepta- 3 = tri-8 = octa- 4 = tetra-9 = nona- 5 = penta-10 = deca-

5. Nomenclature Terms Nonbinary Compound: more than two elements -probably contains polyatomic ion(s) -Name the polyatomic cation first -Name the polyatomic anion second -MUST KNOW the polyatomic ions by name and formula to recognize them

6. Nomenclature Flow Chart

7. Naming of Acids If anion does not contain oxygen: –Start with Hydro- –Add –ic to the end –Ex: HCl: Cl - is chloride, so the acid is Hydrochloric acid If anion contains oxygen: –Look at the ending –If –ite, use anion root and -ous –Ex: HNO 2 : NO 2 - is nitrite, so the acid is Nitrous acid –If –ate, use anion root and -ic –Ex: H2SO 4 : SO 4 2- is sulfate, so the acid is Sulfuric acid

8. Nomenclature Practice Name the following compounds:  Ba(OH) 2  NaC 2 H 3 O 2  Fe 3 (PO 4 ) 2  CaS  MgSO 4  K 2 SO 3  P 2 O 5  N 2 O  SO 3  LiF

9. Monoatomic Cations Metal atoms can lose valence electrons and become positively charged cations. Naming Cations: The parent atom gets the word “ion”. Na +  “sodium ion” Al 3+  “aluminum ion” This rule applies for metals that usually form one ion.

10. Metals That Form Multiple Ions If Metal Forms More than One Cation: The parent metal gets the charge in Roman numerals in parentheses and followed by the word “ion”. Fe 2+ is the iron(II) ion, ferrous (old name) Fe 3+ is the iron(III) ion, ferric (old name) This is called the Stock system of naming cations.

11. Monoatomic Anions Nonmetals can gain valence electrons and become negatively charged anions. Monoatomic anions are named by dropping the end of the element name and adding the suffix –ide.  Br -  “bromide ion” O 2-  “oxide ion” N 3-  “nitride ion”

12. Predicting Cation Formulas Group IA/I metals always form +1 ions and Group IIA/I ions always form +2 ions. Group IIIA/13 metals are predicted to form 3+ ions. Not all metal ion charges are predictable. Tin and lead in Group IVA/14 form both +2 and +4 ions. Most transition metals form +2 ions from the loss of their 2 s- electrons.

13. Metals and Their Cation Charges

14. Predicting Anion Charges Nonmetals gain electrons to form anions Group VIIA/17 atoms gain 1 electron to form -1 ions: F -, Cl -, Br -, and I -  Group VIA/16 atoms gain 2 electrons to form -2 ions: O 2-, S 2-, Se 2-, and Te 2-.  Group VA/15 atoms gain 3 electrons to form -3 ions: N 3-, P 3-, and As 3-.

15. Polyatomic Anions Oxyanions: Polyatomic anions containing one or more elements combined with oxygen are called oxyanions. Most oxyanions have names that end in the suffix -ate. SO 4 2-  “sulfate ion” NO 3 -  “ nitrate ion”

16. Naming Oxyanions  Some oxyanions end in the suffix - ite. NO 2 -  “nitrite ion” SO 3 2-  “sulfite ion”  The oxyanions that end in -ite each have one less oxygen than the oxyanions (compared to the oxyanions ending in –ate, sulfate SO 4 2- and nitrate NO 3 - ).

17. Writing Ionic Formulas Ionic compound: Composed of positive and negative ions. Formula unit shows an ionic compound.  A formula unit is neutral, so the total positive charge must equal the total negative charge in the formula unit.  When writing chemical formulas, the cation (metal) goes first and the anion (nonmetal) goes second.

18. Formulas of Ionic Compounds If the charges of the ions are the same, formula unit contains one of each ion. Na + and Cl - form NaCl. Mg 2+ and S 2- form MgS. If the charges are not equal, balance the positive and negative charges. Ca 2+ and Cl - form CaCl 2. Na + and O 2- form Na 2 O.

19. Formulas with Polyatomic Ions  Follow the same rules as binary ionic compounds; if the charges are equal, the formula has one of each ion. Mg 2+ and SO 4 2- combine to form MgSO 4 K + and ClO 3 - combine to form KClO 3  If the charges are not equal, the total charge must equal zero. If you have more than one polyatomic ion, it is placed in parentheses. Al 3+ and CO 3 2- combine to form Al 2 (CO 3 ) 2.

20. Naming Binary Ionic Compounds Combine the cation and anion name (drop “ion”) in the following order : first cation and second anion. Example: MgO is composed of one magnesium ion and one oxide ion The name is magnesium oxide.

21. Cont’d…Naming Binary Ionic Compounds Question: What is the name of cinnabar, HgS? Hg 2+ is the mercury(II) ion and S 2- is the sulfide ion, The name is mercury(II) sulfide.

22. Naming Ternary Ionic Compounds Name ternary ionic compounds like binary ionic compounds: the cation name followed by the anion name. Example: K 2 CO 3 is named potassium carbonate. If metal can have more than one oxidation state, determine the charge on the metal. Example: Co(ClO 3 ) 3 is composed of cobalt(III) and chlorate ions. cobalt(III) chlorate

23. Binary Molecular Compounds They are composed of two nonmetal elements. A molecule is the simplest representation of a binary molecular compound. IUPAC has set the following order, according to increasing electronegativity, for writing elements in a binary molecular compound: –C, P, N, H, S, I, Br, Cl, O, F

24. Naming Binary Molecular Compounds The first element in the compound is named first and the second element has the suffix -ide. The number of atoms of each element must be indicated by Greek prefixes. PrefixNumber Indicating Mono-1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa8

25. Cont’d…Names of Binary Molecular Compounds Example: What is the name of the molecular compound P 4 S 3 ? –4 P atoms  tetra- –3 S atoms  tri- –P 4 S 3 is tetraphosphorous trisulfide. What is the name for Br 3 O 8 ? –tribromine octaoxide.

26. Exceptions Exception to the use of the Greek prefixes when naming binary molecular compounds. If only one atom exists in the first element “mono-” is not used. The prefix mono- is always used for the second element. –CO is carbon monoxide –IF 6 is iodine hexafluoride

27. Binary Acids  A binary acid is an aqueous solution of a compound containing hydrogen and a nonmetal. The formula of an acid always begins with H: –HF (aq)  Binary acids are named using the prefix hydro- before the element and adding the suffix “-ic acid”. –HF (aq) is hydrofluoric acid –H 2 S (aq) is hydrosulfuric acid

28. Ternary Oxyacids Ternary oxyacids are aqueous solution of a compound containing hydrogen and an oxyanion.  If acid is derived from an oxyanion ending in -ate, suffix is changed to “-ic acid”. HNO 3 (aq) is nitric acid (from NO 3 -, nitrate ion)  If acid is derived from an oxyanion ending in -ite, suffix is changed to “- ous acid”. HNO 2 (aq) is nitrous acid (from NO 2 -, nitrite ion)

29. Lewis Structure for SO 3 1.Count the total number of valence electrons: each oxygen has 6 and sulfur has 6 for a total of 24 electrons [3(6) + 6 = 24 e - ]. This gives us 12 electron pairs. 2.Place 4 electron pairs around the central sulfur atom and attach the three oxygens. We started with 12 electron pairs and have 8 left.

30. 3. Place the remaining electron pairs around the oxygen atoms to complete each octet. 4. One of the oxygens does not have an octet, so move a nonbonding pair from the sulfur to provide 2 pairs between the sulfur and the oxygen. Cont’d…Lewis Structure for SO 3

31. Electronegativity Electronegativity increases from left to right in a period. Electronegativity increases from bottom to top in a group.