4.0-Ionic Compounds Unit

Transcription

1 4.0-Ionic Compounds Unit Objectives: --Given formula, determine if compound is ionic, molecular, or an acid. --Given name, write formula --Given formula, write name --Understand how ionic compounds form --Know properties of ionic compounds

2 Chemical Formulas Indicate the elements present in a compound and the relative (ratio of) number of atoms of each If we change the subscripts in a chemical formula, we no longer represent the same compound. H 2 O is water--- 2 hydrogen : 1 oxygen H 2 O 2 is hydrogen peroxide--- 2 hydrogen : 2 oxygen NaCl--- 1 sodium : 1 chlorine Al 2 (SO 4 ) aluminum : 3 sulfur : 12 oxygen Determine the number of each type of element in the following compounds: 1) Ba 3 N 2 2) Ba 3 (PO 4 ) 2

3 Chemical Formulas Determine the number of each type of element in the following compounds: 1) Ba 3 N 2 2) Ba 3 (PO 4 ) 2 1) 3 barium : 2 nitrogen 2) 3 barium : 2 phosphorus : 8 oxygen When a symbol has no subscript, it is understood to be a 1.

4 Types of Compounds Three types of Compounds: --Ionic: Formula starts with a metal or ammonium Examples: CaCl 2 (NH 4 ) 2 CO 3 AgNO 3 --Acids: formula starts with hydrogen Examples: H 2 S H 2 SO 4 H 3 PO 4 HCl --Molecular: formula contains only nonmetals, hydrogen is not listed first Examples: SOCl 2 C 5 H 10 NH 3

5 Chemical Bonding In chemical reactions, atoms tend to gain, lose, or share electrons so as to achieve the electronic structure of the nearest noble gas. Elements with unstable electron configurations form compounds with other elements to gain stability, low energy state. When atoms gain or lose e s => ionic bonding When atoms share e s => covalent bonding

6 Ionic Bonding Involves the transfer of e s from a metal to a nonmetal. Metal atom(s) gives all of its valence e s to the nonmetal atom(s) to form a positive ion(s). The nonmetal atom(s) gain enough electrons so that its outer energy lever has 8 valence e s to form a negatively charged ion. An ion is an atom that has lost or gained e s.

7 Example: Ionic Bonding Sodium atoms have 1 valence e Chlorine atoms have 7 valence e s. Each sodium will lose 1 valence e. Each chlorine will gain 1 valence e. Result: positively charged sodium ion negatively charged chlorine ion. Because they have opposite charges, they attract each other to form an ionic bond.

8 Ionic Bonding When sodium reacts with chlorine a crystal lattice forms. Chemical formula for an ionic compound shows the lowest whole-number ratio of ions in the lattice. Chemical formula: NaCl Chemical name: sodium chloride. The ratio of sodium ions to chloride ions is 1:1.

9 Ionic Compounds: Example NaCl In a crystal, the sodium ions and chlorine ions alternate in three dimensions to form a crystalline lattice. The crystal is held together by ionic bonds (opposite charges attract)

10 Ionic Compounds When binary ionic compounds form, you must figure out the correct ratio of metal ions to nonmetal ions. Most ionic compounds are crystalline solids at room temperature. In a crystal, the ions are arranged in a repeating, three-dimensional pattern.

11 Properties of Ionic Compounds Many ionic compounds dissolve easily in water to form electrolyte solutions. Such solutions conduct electricity. Ionic compounds are also called salts.

12 Four Important Properties of Ionic Compounds Have high melting points Most dissolve easily in water Conduct electricity when dissolved in water or molten (melted) Exist in crystalline form at room temperature.

13 Using Dot Structures to Represent Ionic Compound Formation See p. 3 of packet Examples

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15 Figure 2.15 Some common monatomic ions of the elements. Hydrogen is a switch hitter! P 3- Ga 3+ Most main-group elements form one monatomic ion. Most transition elements form two monatomic ions.

16 Nonmetal Anion Names Use this when naming a compound Symbol Element Root Anion Symbol Anion Name Br Bromine Brom Br -1 Bromide Cl Chlorine Chlor Cl -1 Chloride F Fluorine Fluor F -1 Fluoride H Hydrogen Hydr H -1 Hydride I Iodine Iod I -1 Iodide N Nitrogen Nitr N -3 Nitride O Oxygen Ox O -2 Oxide P Phosphorus Phosph P -3 Phosphide S Sulfur Sulf S -2 Sulfide

17 Nonmetal Anion Names Use this when naming a compound Symbol Element Root Anion Symbol Anion Name As Arsenic Arsen As -3 Arsenide Se Selenium Selen At Astatine Astat H Hydrogen Hydr Te Tellurium Tellur Assume N all transition Nitrogen metals have Nitr 2 valence O e s, and Oxygen so will form a +2 Ox ion. Except: silver P Phosphorus Phosph Which has 1 valence e, so it forms a +1 ion. S Sulfur Sulf Se -2 At -1 H -1 Te -2 N -3 O -2 P -3 S -2 Selenide Astatide Hydride Telluride Nitride Oxide Phosphide Sulfide

18 Binary Ionic Compounds A-Group Given elements, write formula: Use criss-cross method

19 Bottom p. 5 Given elements, write formula of ions. Criss-cross charges and reduce to write the chemical formula Do not include + or - sign in formula. The subscript 1 does not need to be shown in formula. To name the compounds, write the name of the metal followed by the name of the anion (change non-metal ending to -ide. Ionic compounds contain ions, but overall they are neutral (zero charge). The total negative charge equals the total positive charge.

20 Binary Ionic Compounds-A Group Bottom p. 5 Example: calcium and fluorine 1. Write the formulas for the cation and Ca 2+ F -1 anion, including CHARGES! 2. Criss-cross and reduce Formula for ions: Ca +2 F -1 Formula of compound: CaF 2 Name of compound: calcium fluoride You do potassium and nitrogen CaF 2 1:2 is reduced = CaF 2 A 1 is not written as a subscript.

21 Binary Ionic Compounds-A Group Given name, write formula Example: aluminum and oxygen 1. Write the formulas for the cation and anion, including CHARGES! Al 3+ O 2-2. Criss-cross and reduce. 2 3 Formula for ions: Al +3 O -2 Formula of compound: Al 2 O 3 Name of compound: aluminum oxide = Al 2 O 3 2:3 is reduced You do silver and chlorine

22 Binary Ionic Compounds-A Group Given name, write formula Example: sulfur and zinc 1. Write the formulas for the cation and Zn 2+ S 2- anion, including CHARGES! 2. Criss-cross and reduce Formula for ions: Zn +2 S -2 Formula of compound: ZnS Name of compound: zinc sulfide Finish p.5. Do p.6 for homework Zn 2 S 2 2:2 reduces to 1:1 = ZnS A 1 is not written as a subscript.

23 Binary Ionic Compounds A-Group p.8 When writing a chemical formula: Notice that the cation is always written first and then the anion. There are no + or signs Show the lowest whole-number ratio When writing a name: The metal s name (unchanged) is written first Notice that the anion name always ends in -ide Notice that the number of elements in the compound is not mentioned in the name. Do p. 8 for homework

24 Oxidation Numbers For an ionic compound, the sum of the oxidation numbers in the formula is zero. Consider the compound: Al 2 S 3 How many aluminum ions are represented? What s the charge on each aluminum ion? What s the total positive charge? How many sulfur ions are represented? What s the charge on each sulfur ion? What s the total negative charge?

25 Homework: p. 4a of packet p. 5 of packet p. 6 of packet-binary Ionic Cmpds Practice p. 8 ALWAYS PUT THE METAL FIRST IN FORMULA!

26 Honors Only (p. 9) Previous examples were for compounds that contain a metal cation from groups 1, 2, and 13 (A-Group) For all other metal cations, must add roman numeral to indicate the metal s charge (T-Group)

27 BIC-T Transition Metals Many transition metals form more than one ion. Cu +1 copper (I) Cu +2 copper (II) When naming compounds with these TM s, use a roman numeral to indicated the charge on the metal. CuO Cu 2 O Copper (II) oxide Copper (I) oxide Use the T-Method To get the charge on the metal

28 BIC-T T-Method Given formula, write name Examples: Write name for CuF 2 Write name for Cr 2 O 3 Write name for PbS 2

29 Roman Numeral Rules The following metals do not need a roman numeral in the name of the compound: Group 1, Group 2, Group 13, silver (+1), zinc (+2), and cadmium (+2) The following metals must have a roman numeral in the name of the compound: Groups 3-12, Groups 14-16

30 BIC-T T-Method Given name, write formula Write charges of ions, criss-cross and reduce Examples-See board Write the formula for iron (II) oxide Write the formula for tin (IV) sulfide Write the formula for copper (I) telluride

31 Naming/Writing Formulas BIC-T Group Practice Do 1-10 top Do 1-10 bottom

32 POLYATOMIC IONS Group of atoms that have lost or gained electrons (have a charge). You will be given the list to use on a quiz or test. Below are some examples: NH +1 ammonium 4 C 2 H 3 O 2-1 acetate ClO -1 3 chlorate OH -1 hydroxide NO -1 3 nitrate CO 3-2 carbonate CrO 4-2 chromate SO -2 4 PO -3 4 sulfate phosphate

33 Ionic Compounds with Polyatomic Ions = Ternary Ionic Compounds (TIC) Look at Ionic Compounds Flow Chart TIC A-Group: Contain polyatomic ion with metal that does not need a roman numeral. Example: calcium phosphate = Ca 3 (PO 4 ) 2 TIC T-Group: Contain polyatomic ion with metal that does need a roman numeral. Example: titanium (III) sulfate = Ti 2 (SO 4 ) 3

34 Ternary Ionic Compounds-A Group Given name, write formula Example: Write the formula for barium nitrate 1. Write the formulas for the cation and anion, including CHARGES! Ba 2+ ( NO -1 3 ) 2 2. Criss-cross and reduce 3. Use parentheses if you need more than one of a polyatomic ion. = Ba(NO 3 ) 2 Subscript goes outside the parenthesis. The 3 in nitrate is never changed.

35 Ternary Ionic Compounds-A Group Given name, write formula Example: Write the formula for ammonium sulfate 1. Write the formulas for the cation NH +1 and anion, including CHARGES! 4 SO Criss-cross and reduce. ( ) 2 3. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance the subscripts. = (NH 4 ) 2 SO 4 Subscript goes outside the parenthesis. The 4 in ammonium is never changed.

36 Writing formula for TIC A-Group Write the formula for the following: 1) ammonium oxide 2) calcium phosphate 3) strontium hydroxide 4) magnesium phosphide 5) aluminum sulfide 6) barium sulfate

37 Writing formula for TIC A-Group Write the formula for the following: 1) ammonium oxide = (NH 4 ) 2 O 2) calcium phosphate = Ca 3 (PO 4 ) 2 3) strontium hydroxide = Sr(OH) 2 4) magnesium phosphide = Mg 3 P 2 5) aluminum sulfide = Al 2 S 3 6) barium sulfate = BaSO 4

38 TIC-A Given formula, write name Write the name for Ba(OH) 2 Just name the ions: Barium hydroxide

39 Naming Compounds with Polyatomic Ions TIC A-Group Name the following ionic compounds: 1) NaHCO 3 5) Ba 3 ( PO 4 ) 2 2) K 2 SO 4 6) Ca(OH) 2 3) (NH 4 ) 2 CO 3 7) NH 4 NO 3 4) KC 2 H 3 O 2

40 Naming Compounds with Polyatomic Ions TIC A-Group Answers: NaHCO 3 K 2 SO 3 (NH 4 ) 2 CO 3 KC 2 H 3 O 2 Ba 3 ( PO 4 ) 2 Ca(OH) 2 NH 4 NO 3 = sodium hydrogen carbonate = potassium sulfate = ammonium carbonate = potassium acetate = barium phosphate = calcium hydroxide = ammonium nitrate Complete Ternary Ionic Compounds-No T-Metals WS

41 TIC-T Transition Metals Roman numeral = metal s charge Given formula, write name Write formula for chromium (III) nitrate Cr 3+ and NO 1-3 = Cr(NO 3 ) 3 Must use parenthesis around polyatomic ion when subscript is more than 1.

42 Naming Compounds with Polyatomic Ions TIC T-Group Write the formula for Tin (II) nitrate What does the roman numeral mean? Write formula of ions, criss-cross, and reduce:

43 Naming Compounds with Polyatomic Ions TIC T-Group Honors Only-Write the name for Cu 2 CO 3 Copper (? ) carbonate Use the T-method to determine the charge on copper. More examples (not in packet) Write the name for Pb(NO 3 ) 2 Write the name for CrPO 4 Complete Ternary Compounds WS

44 Ionic Compounds: Writing Formulas Be careful with the endings: sodium phosphide = Na 3 P 2 sodium phosphate = Na 3 PO 4 lithium sulfate = Li 2 SO 4 lithium sulfide = Li 2 S Complete All Ionic Compounds WS

45 Naming Compounds No No No- See other side ASK Ionic YES Begins with a metal or ammonium? Begins with a nonmetal and hydrogen not first? Does metal need a roman numeral? Name the ions. Covalent (Molecular) YES Use T-method to determine charge on metal, then name ions. Examples: AlCl 3 aluminum chloride Mg(NO 3 ) 2 magnesium nitrate NaH sodium hydride NH 4 ClO 2 ammonium chlorite LiOH lithium hydroxide Use prefixes to indicate number of each element. Don t start a name with mono Examples: CuF copper (I) fluoride FeCO 3 iron (II) carbonate PbO 2 lead (IV) oxide Cr 3 (PO 4 ) 2 chromium (II) phosphate Examples: CO 2 carbon dioxide NO nitrogen monoxide S 2 P 4 disulfur tetraphosphide CBr 6 carbon hexabromide

46 No Acid Contains hydrogen and one other kind of nonmetal? Ternary Acid: Contains hydrogen first and a polyatomic ion. Binary Acid: Begin the name with hydro. Use the nonmetal name s stem, add ic. Include the word acid at the end. Don t start the name with hydro. Change the ending on the polyatomic ion: ate ic ite ous Include the word acid at the end. Examples: HCl hydrochloric acid H 2 S hydrosulfuric acid Examples: H 2 SO 3 sulfurous acid HClO 3 chloric acid H 2 SO 2 hyposulfurous acid HNO 4 pernitric acid EXCEPTION TO THIS RULE: HCN hydrocyanic acid