2 Section 6.1 Introduction to Chemical Bonding OBJECTIVES:Distinguish between ionic and molecular compounds.
3 Section 6.1 Introduction to Chemical Bonding OBJECTIVES:Define cation and anion, and relate them to metal and nonmetal.
4 Molecules and Molecular Compounds About 100 different elementsMillions of compounds from themNaming is essential in chemistryNoble gases, such as He and NeIsolated atoms- monatomic, they consist of single atoms
5 Molecules and Molecular Compounds Molecule- smallest electrically neutral unit, still has properties of the substanceMade from only nonmetalsCan be from one element- O2Can make a compound- CO2
6 Molecules and Molecular Compounds Properties of molecular compoundsLow melting and boiling pointsUsually gas or liquidComposed of two or more nonmetalsO2, O3, H2O
7 Systematic NamingThere are too many compounds to remember the names of them all.Compound is made of two or more elements.Put together atoms.Name should tell us how many and what type of atoms.
8 Atoms and ions Atoms are electrically neutral. Same number of protons and electrons.Ions are atoms, or groups of atoms, with a charge (positive or negative)Different numbers of protons and electrons.Only electrons can move.Gain or lose electrons.
9 F1- O2- Anion A negative ion. Has gained electrons. Nonmetals can gain electrons.Charge is written as a superscript on the right.Has gained one electron (-ide is new ending= fluoride)F1-O2-Gained two electrons (oxide)
10 K1+ Ca2+ Cations Positive ions. Formed by losing electrons. More protons than electrons.Metals can lose electronsK1+Has lost one electron (no name change for positive ions)Ca2+Has lost two electrons
11 Ionic CompoundsIonic compounds- from joining metal cations and nonmetal anions- they are electrically neutralUsually solid crystalsMelt at high temperatures
12 Two Types of Compounds Molecular compounds Made of molecules. Made by joining nonmetal atoms together into molecules.
13 Two Types of Compounds Ionic Compounds Made of cations and anions. Metals and nonmetals.The electrons lost by the cation are gained by the anion.The cation and anions surround each other.Smallest piece is a FORMULA UNIT.
14 Two Types of Compounds Ionic Molecular Smallest piece Formula Unit MoleculeTypes of elementsMetal and NonmetalNonmetalsSolid, liquid or gasStatesolidMelting PointHigh >300ºCLow <300ºC
15 Section 6.2 Representing Chemical Compounds OBJECTIVES:Distinguish among chemical formulas, molecular formulas, and formula units.
16 Section 6.2 Representing Chemical Compounds OBJECTIVES:Use experimental data to show that a compound obeys the law of definite proportions.
17 Chemical FormulasShows the kind and number of atoms in the smallest piece of a substance.Molecular formula- number and kinds of atoms in a molecule.CO2C6H12O6
18 Chemical Formulas More than one atom? –use a subscript (H2O) There are 7 diatomic elementsHydrogen (H2), Nitrogen (N2), Oxygen (O2), Fluorine (F2), Chlorine (Cl2), Bromine (Br2), and Iodine (I2)Remember: “Br I N Cl H O F”
19 Ionic CompoundsThis formula represents not a molecule, but a formula unitThe smallest whole number ratio of atoms in an ionic compound.Ions surround each other so you can’t say which is hooked to which. (p. 140)
20 Some Laws:1. Law of Definite Proportions- in a sample of a chemical compound, the masses of the elements are always in the same proportions.H2O (water) and H2O2 (hydrogen peroxide)
21 Some Laws:2. Law of Multiple Proportions- Dalton stated that whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.Figure 6.11, p. 141
22 Section 6.3 Ionic Charges OBJECTIVES: Use the periodic table to determine the charge on an ion.
23 Section 6.3 Ionic Charges OBJECTIVES: Define a polyatomic ion, and give the names and formulas of the most common polyatomic ions.
24 Charges on ionsFor most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location; monatomic ionsElements in the same group have similar properties.Including the charge when they are ions.
26 What about the others?Groups 4A and 0 do not usually form ions (in fact, Group 0 rarely forms compounds!)Many transition metals have more than one common ionic charge
27 Naming ions Two methods if more than one charge is possible: 1. Stock system – uses roman numerals in parenthesis to indicate the numerical value2. Classical method – uses root word with suffixes (-ous, -ic)Does not give true value
28 Naming ions Use the Stock or Classical system. Cation- if the charge is always the same (Group A) just write the name of the metal.Transition metals can have more than one type of charge.Indicate the charge with roman numerals in parenthesis (Table 6.3, p.144) or end with -ous or -ic.
39 Write theseSulfide ioniodide ionphosphide ionStrontium ion
40 Exceptions:Some of the transition metals have only one ionic charge:Do not use roman numerals for these:Silver is always 1+ (Ag1+)Cadmium and Zinc are always 2+ (Cd2+ and Zn2+)Note Fig. 6.13, p. 145
41 Polyatomic ions Groups of atoms that stay together and have a charge. Learn these - Table 6.4, p.147Acetate C2H3O21-Nitrate NO31-Nitrite NO21-Hydroxide OH1- and Cyanide CN1-Permanganate MnO41-
43 Section 6.4 Ionic Compounds OBJECTIVES:Apply the rules for naming and writing formulas for binary ionic compounds.
44 Section 6.4 Ionic Compounds OBJECTIVES:Apply the rules for naming and writing formulas for ternary ionic compounds.
45 Naming Binary Ionic Compounds Binary Compounds - 2 elements.Ionic - a cation and an anion.To write the names, just name the two ions.Easy with Representative elements (which are Group A elements)NaCl = Na1+ Cl1- = sodium chlorideMgBr2 = Mg2+ Br1- = magnesium bromide
46 Naming Binary Ionic Compounds The problem comes with the transition metals.Need to figure out their charges.The compound must be neutral.same number of + and – charges.Use the anion to determine the charge on the positive ion.
47 Naming Binary Ionic Compounds Write the name of CuONeed the charge of CuO is 2-copper must be 2+Copper (II) oxideName CoCl3Cl is 1- and there are three of them = 3-Co must be 3+ Cobalt (III) chloride
48 Naming Binary Ionic Compounds Write the name of Cu2S.Since S is 2-, the Cu2 must be 2+, so each one is 1+.copper (I) sulfideFe2O3Each O is x -2 = -62 Fe must = 6+, so each is 3+.iron (III) oxide
49 Naming Binary Ionic Compounds Write the names of the followingKClNa3NCrNSc3P2PbOPbO2Na2Se
50 Ternary Ionic Compounds These will have polyatomic ionsAt least three elementsname the ionsNaNO3CaSO4CuSO3(NH4)2O
52 Writing Formulas The charges have to add up to zero. Get charges on pieces.Cations from name on table.Anions from table or polyatomic.Balance the charges by adding subscripts.Put polyatomics in parenthesis.
53 Writing Formulas Write the formula for calcium chloride. Calcium is Ca2+Chloride is Cl1-Ca2+ Cl1- would have a 1+ charge.Need another Cl1-Ca2+ Cl21- (use criss-cross method)
54 Write the formulas for these Lithium sulfidetin (II) oxidetin (IV) oxideMagnesium fluorideCopper (II) sulfateIron (III) phosphidegallium nitrateIron (III) sulfide
55 Write the formulas for these Ammonium chlorideammonium sulfidebarium nitrate
56 Things to look forIf cations have ( ), the number in parenthesis is their charge.If anions end in -ide they are probably off the periodic table (Monoatomic)If anion ends in -ate or -ite it is polyatomic
57 Section 6.5 Molecular Compounds and Acids OBJECTIVES:Apply the rules for naming and writing formulas for binary molecular compounds.
58 Section 6.5 Molecular Compounds and Acids OBJECTIVES:Name and write formulas for common acids.
59 Molecular compounds made of just nonmetals smallest piece is a moleculecan’t be held together because of opposite charges.can’t use charges to figure out how many of each atom
60 Molecular are easier!Ionic compounds use charges to determine how many of each.Have to figure out charges.Have to figure out numbers.Molecular compounds name tells you the number of atoms.Uses prefixes to tell you the number
62 Prefixes9 = nona-10 = deca-To write the name, write two words:
63 Prefixes Prefix name Prefix name -ide 9 = nona- 10 = deca- To write the name, write two words:PrefixnamePrefixname-ide
64 Prefixes Prefix name Prefix name -ide 9 = nona- 10 = deca- To write the name, write two words:One exception is we don’t write mono- if there is only one of the first element.PrefixnamePrefixname-ide
65 Prefixes Prefix name Prefix name -ide 9 = nona- 10 = deca- To write the name, write two words:One exception is we don’t write mono- if there is only one of the first element.No double vowels when writing names (oa oo)PrefixnamePrefixname-ide
67 Write formulas for these diphosphorus pentoxidetetraiodine nonoxidesulfur hexafluoridenitrogen trioxidecarbon tetrahydridephosphorus trifluoridealuminum chloride
68 Writing names and Formulas AcidsWriting names and Formulas
69 Acids Compounds that give off hydrogen ions when dissolved in water. Must have H in them.will always be some H next to an anion.The anion determines the name.
70 Naming acidsIf the anion attached to hydrogen ends in -ide, put the prefix hydro- and change -ide to -ic acidHCl - hydrogen ion and chloride ionhydrochloric acidH2S hydrogen ion and sulfide ionhydrosulfuric acid
71 Naming AcidsIf the anion has oxygen in it, then it ends in -ate of -itechange the suffix -ate to -ic acid (use no prefix)HNO3 Hydrogen and nitrate ionsNitric acidchange the suffix -ite to -ous acidHNO2 Hydrogen and nitrite ionsNitrous acid
73 Writing Acid Formulas Hydrogen will always be first name will tell you the anionmake the charges cancel out.Starts with hydro?- no oxygen, -ideno hydro?, -ate comes from -ic, -ite comes from -ous
74 Write formulas for these hydroiodic acidacetic acidcarbonic acidphosphorous acidhydrobromic acid
75 Section 6.6 Summary of Naming and Formula Writing OBJECTIVES:Use the flowchart in Figure 6.21 to write the name of a compound when given its chemical formula.
76 Section 6.6 Summary of Naming and Formula Writing OBJECTIVES:Use the flowchart in Figure 6.23 to write a chemical formula when given the name of a compound.
77 Helpful to remember...1. In an ionic compound, the net ionic charge is zero (criss-cross method)2. An -ide ending generally indicates a binary compound3. An -ite or -ate ending means there is a polyatomic ion that has oxygen4. Prefixes generally mean molecular; they show the number of each atom
78 Helpful to remember...5. A Roman numeral after the name of a cation shows the ionic charge of the cationUse the handout sheets provided by your teacher!
79 Summary of Naming and Formula Writing For naming, follow the flowchart- Fig. 6.21, page 161For writing formulas, follow the flowchart from Fig. 6.23, p. 162