Section 6.1 Introduction to Chemical Bonding l OBJECTIVES: –Distinguish between ionic and molecular compounds.
Section 6.1 Introduction to Chemical Bonding l OBJECTIVES: –Define cation and anion, and relate them to metal and nonmetal.
Molecules and Molecular Compounds l About 100 different elements l Millions of compounds from them l Naming is essential in chemistry l Noble gases, such as He and Ne l Isolated atoms- monatomic, they consist of single atoms
Molecules and Molecular Compounds l Molecule- smallest electrically neutral unit, still has properties of the substance l Made from only nonmetals l Can be from one element- O 2 l Can make a compound- CO 2
Molecules and Molecular Compounds l Properties of molecular compounds –Low melting and boiling points –Usually gas or liquid –Composed of two or more nonmetals –O 2, O 3, H 2 O
Systematic Naming l There are too many compounds to remember the names of them all. l Compound is made of two or more elements. l Put together atoms. l Name should tell us how many and what type of atoms.
Atoms and ions l Atoms are electrically neutral. l Same number of protons and electrons. l Ions are atoms, or groups of atoms, with a charge (positive or negative) l Different numbers of protons and electrons. l Only electrons can move. l Gain or lose electrons.
Anion l A negative ion. l Has gained electrons. l Nonmetals can gain electrons. l Charge is written as a superscript on the right. F 1- Has gained one electron (-ide is new ending= fluoride) O 2- Gained two electrons (oxide)
Cations l Positive ions. l Formed by losing electrons. l More protons than electrons. l Metals can lose electrons K 1+ Has lost one electron (no name change for positive ions) Ca 2+ Has lost two electrons
Ionic Compounds l Ionic compounds- from joining metal cations and nonmetal anions- they are electrically neutral l Usually solid crystals l Melt at high temperatures
Two Types of Compounds Molecular compounds l Made of molecules. l Made by joining nonmetal atoms together into molecules.
Two Types of Compounds Ionic Compounds l Made of cations and anions. l Metals and nonmetals. l The electrons lost by the cation are gained by the anion. l The cation and anions surround each other. l Smallest piece is a FORMULA UNIT.
Two Types of Compounds Smallest piece Melting Point State Types of elements Formula UnitMolecule Metal and Nonmetal Nonmetals solid Solid, liquid or gas High >300ºCLow <300ºC IonicMolecular
Section 6.2 Representing Chemical Compounds l OBJECTIVES: –Distinguish among chemical formulas, molecular formulas, and formula units.
Section 6.2 Representing Chemical Compounds l OBJECTIVES: –Use experimental data to show that a compound obeys the law of definite proportions.
Chemical Formulas l Shows the kind and number of atoms in the smallest piece of a substance. l Molecular formula- number and kinds of atoms in a molecule. l CO 2 l C 6 H 12 O 6
Chemical Formulas l More than one atom? –use a subscript (H 2 O) l There are 7 diatomic elements l Hydrogen (H 2 ), Nitrogen (N 2 ), Oxygen (O 2 ), Fluorine (F 2 ), Chlorine (Cl 2 ), Bromine (Br 2 ), and Iodine (I 2 ) l Remember: “Br I N Cl H O F”
Ionic Compounds l This formula represents not a molecule, but a formula unit l The smallest whole number ratio of atoms in an ionic compound. l Ions surround each other so you can’t say which is hooked to which. (p. 140)
Some Laws: l 1. Law of Definite Proportions- in a sample of a chemical compound, the masses of the elements are always in the same proportions. l H 2 O (water) and H 2 O 2 (hydrogen peroxide)
Some Laws: l 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. l Figure 6.11, p. 141
Section 6.3 Ionic Charges l OBJECTIVES: –Use the periodic table to determine the charge on an ion.
Section 6.3 Ionic Charges l OBJECTIVES: –Define a polyatomic ion, and give the names and formulas of the most common polyatomic ions.
Charges on ions l For most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location; monatomic ions l Elements in the same group have similar properties. l Including the charge when they are ions.
What about the others? l Groups 4A and 0 do not usually form ions (in fact, Group 0 rarely forms compounds!) l Many transition metals have more than one common ionic charge
Naming ions l Two methods if more than one charge is possible: –1. Stock system – uses roman numerals in parenthesis to indicate the numerical value –2. Classical method – uses root word with suffixes (-ous, -ic) Does not give true value
Naming ions l Use the Stock or Classical system. l Cation- if the charge is always the same (Group A) just write the name of the metal. l Transition metals can have more than one type of charge. l Indicate the charge with roman numerals in parenthesis (Table 6.3, p.144) or end with -ous or -ic.
Name these l Na 1+ l Ca 2+ l Al 3+ l Fe 3+ l Fe 2+ l Pb 2+ l Li 1+
Write Formulas for these l Potassium ion l Magnesium ion l Copper (II) ion l Chromium (I) ion l Barium ion l Mercury (II) ion
Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluorine
Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluorin
Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluori
Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluor
Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluori
Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluorid
Naming Anions l Anions are always the same charge l Change the element ending to – ide l F 1- Fluoride
Name these l Cl 1- l N 3- l Br 1- l O 2- l Ga 3+
Write these l Sulfide ion l iodide ion l phosphide ion l Strontium ion
Exceptions: l Some of the transition metals have only one ionic charge: –Do not use roman numerals for these: –Silver is always 1+ (Ag 1+ ) –Cadmium and Zinc are always 2+ (Cd 2+ and Zn 2+ ) l Note Fig. 6.13, p. 145
Polyatomic ions l Groups of atoms that stay together and have a charge. l Learn these - Table 6.4, p.147 l Acetate C 2 H 3 O 2 1- l Nitrate NO 3 1- l Nitrite NO 2 1- l Hydroxide OH 1- and Cyanide CN 1- l Permanganate MnO 4 1-
Polyatomic ions l Sulfate SO 4 2- l Sulfite SO 3 2- l Carbonate CO 3 2- l Chromate CrO 4 2- l Dichromate Cr 2 O 7 2- l Phosphate PO 4 3- l Phosphite PO 3 3- l Ammonium NH 4 1+
Section 6.4 Ionic Compounds l OBJECTIVES: –Apply the rules for naming and writing formulas for binary ionic compounds.
Section 6.4 Ionic Compounds l OBJECTIVES: –Apply the rules for naming and writing formulas for ternary ionic compounds.
Naming Binary Ionic Compounds l Binary Compounds - 2 elements. l Ionic - a cation and an anion. l To write the names, just name the two ions. l Easy with Representative elements (which are Group A elements) l NaCl = Na 1 + Cl 1 - = sodium chloride l MgBr 2 = Mg 2+ Br 1 - = magnesium bromide
Naming Binary Ionic Compounds l The problem comes with the transition metals. l Need to figure out their charges. l The compound must be neutral. l same number of + and – charges. l Use the anion to determine the charge on the positive ion.
Naming Binary Ionic Compounds l Write the name of CuO l Need the charge of Cu l O is 2- l copper must be 2+ l Copper (II) oxide l Name CoCl 3 l Cl is 1- and there are three of them = 3- l Co must be 3+ Cobalt (III) chloride
Naming Binary Ionic Compounds l Write the name of Cu 2 S. l Since S is 2-, the Cu 2 must be 2+, so each one is 1+. l copper (I) sulfide l Fe 2 O 3 l Each O is 2- 3 x -2 = -6 l 2 Fe must = 6+, so each is 3+. l iron (III) oxide
Naming Binary Ionic Compounds l Write the names of the following l KCl l Na 3 N l CrN l Sc 3 P 2 l PbO l PbO 2 l Na 2 Se
Ternary Ionic Compounds l These will have polyatomic ions l At least three elements l name the ions l NaNO 3 l CaSO 4 l CuSO 3 l (NH 4 ) 2 O
Ternary Ionic Compounds l LiCN l Fe(OH) 3 l (NH 4 ) 2 CO 3 l NiPO 4
Writing Formulas l The charges have to add up to zero. l Get charges on pieces. l Cations from name on table. l Anions from table or polyatomic. l Balance the charges by adding subscripts. l Put polyatomics in parenthesis.
Writing Formulas l Write the formula for calcium chloride. l Calcium is Ca 2+ l Chloride is Cl 1- l Ca 2+ Cl 1- would have a 1+ charge. l Need another Cl 1- l Ca 2+ Cl 2 1- (use criss-cross method)
Write the formulas for these l Lithium sulfide l tin (II) oxide l tin (IV) oxide l Magnesium fluoride l Copper (II) sulfate l Iron (III) phosphide l gallium nitrate l Iron (III) sulfide
Write the formulas for these l Ammonium chloride l ammonium sulfide l barium nitrate
Things to look for l If cations have ( ), the number in parenthesis is their charge. l If anions end in -ide they are probably off the periodic table (Monoatomic) l If anion ends in -ate or -ite it is polyatomic
Section 6.5 Molecular Compounds and Acids l OBJECTIVES: –Apply the rules for naming and writing formulas for binary molecular compounds.
Section 6.5 Molecular Compounds and Acids l OBJECTIVES: –Name and write formulas for common acids.
Molecular compounds l made of just nonmetals l smallest piece is a molecule l can’t be held together because of opposite charges. l can’t use charges to figure out how many of each atom
Molecular are easier! l Ionic compounds use charges to determine how many of each. –Have to figure out charges. –Have to figure out numbers. l Molecular compounds name tells you the number of atoms. l Uses prefixes to tell you the number
Prefixes (Table 6.5, p.159) l 1 = mono- l 2 = di- l 3 = tri- l 4 = tetra- l 5 = penta- l 6 = hexa- l 7 = hepta- l 8 = octa-
Prefixes l 9 = nona- l 10 = deca- l To write the name, write two words:
Prefixes l 9 = nona- l 10 = deca- l To write the name, write two words: PrefixnamePrefixname-ide
Prefixes l 9 = nona- l 10 = deca- l To write the name, write two words: l One exception is we don’t write mono- if there is only one of the first element. PrefixnamePrefixname-ide
Prefixes l 9 = nona- l 10 = deca- l To write the name, write two words: l One exception is we don’t write mono- if there is only one of the first element. l No double vowels when writing names (oa oo) PrefixnamePrefixname-ide
Name These lN2OlN2O l NO 2 l Cl 2 O 7 l CBr 4 l CO 2 l BaCl 2
Write formulas for these l diphosphorus pentoxide l tetraiodine nonoxide l sulfur hexafluoride l nitrogen trioxide l carbon tetrahydride l phosphorus trifluoride l aluminum chloride
Acids l Compounds that give off hydrogen ions when dissolved in water. l Must have H in them. l will always be some H next to an anion. l The anion determines the name.
Naming acids l If the anion attached to hydrogen ends in -ide, put the prefix hydro- and change -ide to -ic acid l HCl - hydrogen ion and chloride ion l hydrochloric acid l H 2 S hydrogen ion and sulfide ion l hydrosulfuric acid
Naming Acids l If the anion has oxygen in it, then it ends in -ate of -ite l change the suffix -ate to -ic acid (use no prefix) l HNO 3 Hydrogen and nitrate ions l Nitric acid l change the suffix -ite to -ous acid l HNO 2 Hydrogen and nitrite ions l Nitrous acid
Name these l HF lH3PlH3P l H 2 SO 4 l H 2 SO 3 l HCN l H 2 CrO 4
Writing Acid Formulas l Hydrogen will always be first l name will tell you the anion l make the charges cancel out. l Starts with hydro?- no oxygen, -ide l no hydro?, -ate comes from -ic, -ite comes from -ous
Write formulas for these l hydroiodic acid l acetic acid l carbonic acid l phosphorous acid l hydrobromic acid
Section 6.6 Summary of Naming and Formula Writing l OBJECTIVES: –Use the flowchart in Figure 6.21 to write the name of a compound when given its chemical formula.
Section 6.6 Summary of Naming and Formula Writing l OBJECTIVES: –Use the flowchart in Figure 6.23 to write a chemical formula when given the name of a compound.
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 compound 3. An -ite or -ate ending means there is a polyatomic ion that has oxygen 4. Prefixes generally mean molecular; they show the number of each atom
Helpful to remember... 5. A Roman numeral after the name of a cation shows the ionic charge of the cation l Use the handout sheets provided by your teacher!
Summary of Naming and Formula Writing l For naming, follow the flowchart- Fig. 6.21, page 161 l For writing formulas, follow the flowchart from Fig. 6.23, p. 162