Chapter 5 Nomenclature Chemical BONDING Chemical Bond • A bond results from the attraction of nuclei for electrons – All atoms trying to achieve a stable octet • IN OTHER WORDS – the p+ in one nucleus are attracted to the e- of another atom • Electronegativity • Molecule: 2 or more atoms joined by a chemical bond • Compound: a molecule composed of atoms of 2 or more different elements bonded together in a fixed ratio Diatomic Molecule • Diatomic Molecule: a molecule containing 2 atoms • The Diatomic molecules are: • Hydrogen (H2) Nitrogen (N2) Oxygen (O2) Fluorine (F2) Chlorine (Cl2) Iodine (I2) Bromine (Br2) • Chemical formula: represents the relative numbers of atoms of each kind in a chemical compound by using atomic symbols and numeric subscripts • Bond energy: the energy required to break a chemical bond and form neutral atoms Naming Compounds Types of Chemical Bonds: (4) 1. 2. 3. 4. Ionic bonds Covalent bonds Metallic bonds Hydrogen bonds Return to TOC Copyright © Cengage Learning. All rights reserved 7 Bond Formation • exothermic process E N E R G Y Reactants Energy released Products Breaking Bonds • Endothermic reaction – energy must be put into the bond in order to break it E N E R G Y Reactants Products Energy Absorbed Bond Strength • Strong, STABLE bonds require lots of energy to be formed or broken • weak bonds require little E Two Major Types of Bonding • Ionic Bonding – forms ionic compounds – transfer of e- • Covalent Bonding – forms molecules – sharing e- Naming Compounds Return to TOC One minor type of bonding • Metallic bonding – Occurs between like atoms of a metal in the free state – Valence e- are mobile (move freely among all metal atoms) – Positive ions in a sea of electrons • Metallic characteristics – High mp temps, ductile, malleable, shiny – Hard substances – Good conductors of heat and electricity as (s) and (l) It’s the mobile electrons that enable me tals to conduct electricity!!!!!! IONic Bonding • electrons are transferred between valence shells of atoms • ionic compounds are NOT MOLECULES made of ions • ionic compounds are called Salts or Crystals IONic bonding • Always formed between metals and non-metals + [METALS ] [NON-METALS ] Lost e- Gained e- Properties of Ionic Compounds SALTS Crystals • hard solid @ 22oC • high mp temperatures • nonconductors of electricity in solid phase • good conductors in liquid phase or dissolved in water (aq) Covalent Bonding molecules • Pairs of e- are shared between non-metal atoms • electronegativity difference < 2.0 • forms polyatomic ions Properties of Molecular Substances Covalent bonding • Low m.p. temp and b.p. temps • relatively soft solids as compared to ionic compounds • nonconductors of electricity in any phase Covalent, Ionic, metallic bonding? • NO2 • sodium hydride • Hg • H2S • sulfate • NH4+ • CO • Aluminum • Co phosphate • KH Can You Tell • KCl What type of • HF bond is formed Drawing ionic compounds using Lewis Dot Structures • Symbol represents the KERNEL of the atom (nucleus and inner e-) • dots represent valence e- NaCl • This is the finished Lewis Dot Structure How did we get here? + [Na] - [ Cl ] • Step 1 after checking that it is IONIC – Determine which atom will be the +ion – Determine which atom will be the - ion • Step 2 – Write the symbol for the + ion first. • NO DOTS – Draw the e- dot diagram for the – ion • COMPLETE outer shell • Step 3 – Enclose both in brackets and show each charge Draw the Lewis Diagrams • LiF • MgO • CaCl2 • K2S Drawing molecules using Lewis Dot Structures • Symbol represents the KERNEL of the atom (nucleus and inner e-) • dots represent valence e- Always remember atoms are trying to complete their outer shell! The number of electrons the atoms needs is the total number of bonds they can make. Ex. … H? O? F? N? Cl? C? one two one three one four Methane CH4 • This is the finished Lewis dot structure How did we get here? • Step 1 – count total valence e- involved • Step 2 – connect the central atom (usually the first in the formula) to the others with single bonds • Step 3 – complete valence shells of outer atoms • Step 4 – add any extra e- to central atom IF the central atom has 8 valence e- surrounding it . . YOU’RE DONE! Sometimes . . . • You only have two atoms, so there is no central atom, but follow the same rules. • Check & Share to make sure all the atoms are “happy”. Cl2 Br2 H2 O2 N2 HCl • DOUBLE bond – atoms that share two e- pairs (4 e-) O O • TRIPLE bond – atoms that share three e- pairs (6 e-) N N Draw Lewis Dot Structures You may represent valence electrons from different atoms with the following symbols x, , CO2 NH3 Draw the Lewis Dot Diagram for polyatomic ions • Count all valence e- needed for covalent bonding • Add or subtract other electrons based on the charge REMEMBER! A positive charge means it LOST electrons!!!!! Draw Polyatomics • Ammonium • Sulfate Types of Covalent Bonds • NON-Polar bonds – Electrons shared evenly in the bond – E-neg difference is zero Between identical atoms Diatomic molecules Types of Covalent Bonds Polar bond – Electrons unevenly shared non-polar MOLECULES • Sometimes the bonds within a molecule are polar and yet the molecule is non-polar because its shape is symmetrical. H H C H Draw Lewis dot first and see if equal on all sides H Polar molecules (a.k.a. Dipoles) • Not equal on all sides – Polar bond between 2 atoms makes a polar molecule – asymmetrical shape of molecule + H Cl Water is asymmetrical + O - H + H Water is a bent molecule H H O H H W-A-T-E-R as bent as it can be! Water’s polar MOLECULE! Water’s polar MOLECULE! The H is positive The O is not - not - not - not Making sense of the polar non-polar thing BONDS Non-polar Polar Identical Different MOLECULES Non-polar Symmetrical Polar Asymmetrical IONIC bonds …. Ionic bonds are so polar that the electrons are not shared but transferred between atoms forming ions!!!!!! 4 Shapes of molecules Linear (straight line) Ball and stick model Space filling model Bent Ball and stick model Space filling model Trigonal pyramid Ball and stick model Space filling model Tetrahedral Ball and stick model Space filling model Intermolecular attractions • Attractions between molecules – van der Waals forces • Weak attractive forces between non-polar molecules – Hydrogen “bonding” • Strong attraction between special polar molecules van der Waals • Non-polar molecules can exist in liquid and solid phases because van der Waals forces keep the molecules attracted to each other • Exist between CO2, CH4, CCl4, CF4, diatomics and monoatomics van der Waals periodicity • increase with molecular mass. – Greater van der Waals force? • F2 Cl2 Br2 I2 • increase with closer distance between molecules – Decreases when particles are farther away Hydrogen “Bonding” • Strong polar attraction – Like magnets • Occurs ONLY between H of one molecule and N, O, F of another H “bond” Why does H “bonding” occur? • Nitrogen, Oxygen and Fluorine – small atoms with strong nuclear charges • powerful atoms – very high electronegativities Intermolecular forces dictate chemical properties • Strong intermolecular forces cause high b.p., m.p. and slow evaporation (low vapor pressure) of a substance. Which substance has the highest boiling point? • HF • NH3 • H2O Fluorine has the highest e-neg, SO HF will experience the • WHY? needs the most energy to weaken the i.m.f. and boil strongest H bonding and Density???? H2O(s) is less dense than H2O(l) • The hydrogen bonding in water(l) molecules is random. The molecules are closely packed. • The hydrogen bonding in water(s) molecules has a specific open lattice pattern. The molecules are farther apart. Naming Compounds Chemical Names and formulas • With all of the compounds and all of the elements to be identified, a systematic method for writing formulas and naming compounds is necessary • A correctly written chemical formula must represent the known facts about the composition of a compound • Care must be taken so that subscripts are correct Return to TOC Copyright © Cengage Learning. All rights reserved 67 Naming Compounds Using Chemical formulas • Chemical formulas indicate the elements present in a compound and the relative numbers of atoms of each element in the compound • In chemical formulas, the elements are given by their symbols and the relative number of atoms of each element by numerical subscript • Ex H2SO4 the H, S & O are symbols, the 2 & 4 are subscripts Return to TOC Copyright © Cengage Learning. All rights reserved 68 Naming Compounds Return to TOC • Ion: A charged particle due to loss or gain of electrons • Cation: positive charge ion represented by a (+) after the chemical symbol (metal) Ex Na+ • Anion: negative charge ion represented by a (-) after the chemical symbol (metal) Ex Cl- Naming Compounds Monatomic Ions • Positive ions are named by the element name followed by the word “ion” • Examples : • K+ potassium ion magnesium ion Mg+2 aluminum ion • Al+3 Return to TOC Copyright © Cengage Learning. All rights reserved 72 Naming Compounds • Negative ions are named by dropping the ending of the element name and adding the ending “ide” to it followed by the word “ion” • • • • Examples: FS-2 I- fluoride ion sulfide ion Iodide ion Return to TOC Copyright © Cengage Learning. All rights reserved 73 Naming Compounds Learning Check Give the names of the following ions: Ba2+ _________ Al3+ __________ K+ _________ N3 _________ O2 __________ F _________ P3 _________ S2 __________ Cl _________ 74 Return to TOC Naming Compounds Solution Ba2+ barium Al3+ aluminum K+ potassium N3 nitride O2 oxide F fluoride P3 phosphide S2 sulfide Cl chloride 75 Return to TOC Naming Compounds • Binary Compounds • Binary Ionic Compounds • Composed of two elements Metal—nonmetal Binary Covalent Compounds Nonmetal—nonmetal Return to TOC Copyright © Cengage Learning. All rights reserved 76 Naming Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 77 Naming Compounds • Binary ionic compounds contain positive cations and negative anions. Type I compounds • Metal present forms only one cation. Type II compounds • Metal present can form 2 or more cations with different charges. Return to TOC Copyright © Cengage Learning. All rights reserved 78 Naming Compounds Type I Compounds Metals (Groups I, II, and III) and Non-Metals Metal _________ Sodium + Non-Metal _________ide Chlorine Sodium Chloride NaCl Return to TOC 79 Naming Compounds Common Simple Cations and Anions Return to TOC Copyright © Cengage Learning. All rights reserved 80 Naming Compounds Rules for Naming Type I Ionic Compounds 1. The cation is always named first and the anion second. 2. A simple cation takes its name from the name of the element. 3. A simple anion is named by taking the first part of the element name (the root) and adding –ide. Return to TOC Copyright © Cengage Learning. All rights reserved 81 Naming Compounds Binary Ionic Compounds (Type I) • Examples: KCl Potassium chloride MgBr2 Magnesium bromide CaO Calcium oxide Return to TOC Copyright © Cengage Learning. All rights reserved 82 Naming Compounds Exercise What is the name of the compound SrBr2? a) b) c) d) strontium bromine sulfur bromide strontium dibromide strontium bromide Return to TOC Copyright © Cengage Learning. All rights reserved 83 Naming Compounds • Strontium bromide. Sr is the symbol for strontium. • Br is the symbol for bromine, • take the first part of the element name (the root) and add –ide to get the name bromide. Return to TOC Copyright © Cengage Learning. All rights reserved 84 Naming Compounds Binary Ionic Compounds (Type II) • • • • Metals in these compounds can form more than one type of positive charge. Charge on the metal ion must be specified. Roman numeral indicates the charge of the metal cation. Transition metal cations usually require a Roman numeral. Copyright © Cengage Learning. All rights reserved Return to TOC 85 Naming Compounds Type II Compounds Metals (Transition Metals) and Non-Metals Metal ______ Iron +Roman Numeral (__) III + Non-Metal ________ide Bromine Iron (III) Bromide FeBr3 Compare with Iron (II) Bromide FeBr2 Metals (Transition Metals) and Non-Metals Older System Metal (Latin) _______ Ferrous + ous or ic + Non-Metal ________ide Bromine Ferrous Bromide FeBr2 Compare with Ferric Bromide FeBr3 Return to TOC 86 Naming Compounds Different names are needed for positive ions of 2 different charges formed by the same metal • Old system: “ous” ending for lower charge • “ic” ending for higher charge • New system: gives actual charge on the ion as a roman numeral Return to TOC Copyright © Cengage Learning. All rights reserved 87 Naming Compounds Common Type II Cations Return to TOC Copyright © Cengage Learning. All rights reserved 88 Naming Compounds Rules for Naming Type II Ionic Compounds 1. The cation is always named first and the anion second. 2. Because the cation can assume more than one charge, the charge is specified by a Roman numeral in parentheses. Return to TOC Copyright © Cengage Learning. All rights reserved 89 Naming Compounds Binary Ionic Compounds (Type II) • Examples: CuBr Copper(I) bromide FeS Iron(II) sulfide PbO2 Lead(IV) oxide Return to TOC Copyright © Cengage Learning. All rights reserved 90 Naming Compounds Exercise What is the name of the compound CrO2? a) b) c) d) chromium oxide chromium(II) oxide chromium(IV) oxide chromium dioxide Return to TOC Copyright © Cengage Learning. All rights reserved 91 Naming Compounds • Chromium(IV) oxide. Cr is the symbol for chromium. O is the symbol for oxygen, but • take the first part of the element name (the root) and add –ide to get the name oxide. • Since chromium can have more than one charge, a Roman numeral must be used to identify that charge. • There are two oxygen ions each with a 2– charge, giving an overall charge of –4. • Therefore, the charge on chromium must be +4. Return to TOC Copyright © Cengage Learning. All rights reserved 92 Naming Compounds Exercise What is the correct name of the compound that results from the most stable ion for sulfur and the metal ion that contains 24 electrons? a) b) c) d) iron(III) sulfide chromium(II) sulfide nickel(III) sulfate iron(II) sulfide Return to TOC Copyright © Cengage Learning. All rights reserved 93 Naming Compounds • Iron(II) sulfide. • For sulfur, take the first part of the element name (the root) and add –ide to get the name sulfide. • Iron with a +2 charge (as the Roman numeral indicates) contains 24 electrons (26p – 24e = +2 charge). Return to TOC Copyright © Cengage Learning. All rights reserved 94 Naming Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 95 Naming Compounds Rules for Naming Type III Binary Compounds • Formed between two nonmetals. 1. The first element in the formula is named first, and the full element name is used. 2. The second element is named as though it were an anion. 3. Prefixes are used to denote the numbers of atoms present. 4. The prefix mono- is never used for naming the first element. Return to TOC Copyright © Cengage Learning. All rights reserved 96 Naming Compounds Type III Compounds Non-Metals and Non-Metals Use Prefixes such as mono, di, tri, tetra, penta, hexa, hepta, etc. CO2 Carbon dioxide CO Carbon monoxide PCl3 Phosphorus trichloride CCl4 Carbon tetrachloride N2O5 Dinitrogen pentoxide CS2 Carbon disulfide Return to TOC Copyright © Cengage Learning. All rights reserved 97 Naming Compounds Prefixes Used to Indicate Numbers in Chemical Names Additional Prefixes 9 nona- 10 deca- 11 undeca- 12 dodeca- 13 trideca- 14 tetradeca- 15 pentadeca- 16 hexadeca- 17 heptadeca- 18 octadeca- 19 nonadeca- 20 icosa Return to TOC Copyright © Cengage Learning. All rights reserved 98 Naming Compounds Binary Covalent Compounds (Type III) • Examples: CO2 Carbon dioxide SF6 Sulfur hexafluoride N2O4 Dinitrogen tetroxide Return to TOC Copyright © Cengage Learning. All rights reserved 99 Naming Compounds Exercise What is the name of the compound SeO2? a) b) c) d) selenium oxide selenium dioxide selenium(II) oxide selenium(IV) dioxide Return to TOC Copyright © Cengage Learning. All rights reserved 100 Naming Compounds • • • • Selenium dioxide. Se is the symbol for selenium. O is the symbol for oxygen, take the first part of the element name (the root) and add –ide to get the name oxide. • Since they are both nonmetals, prefixes are used to identify the elements (except mono- is not used for the first element). • Two oxygen atoms require the use of the prefix di-, making the name dioxide. Return to TOC Copyright © Cengage Learning. All rights reserved 101 Naming Compounds Flow Chart for Naming Binary Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 102 Let’s Practice! Naming Compounds Name the following. CaF2 K2S CoI2 SnF2 SnF4 OF2 CuI2 CuI SO2 SrS LiBr Calcium Flouride Potassium Sulfide Cobalt (II) Iodide or Cobaltous Iodide Tin (II) Fluoride or Stannous Fluoride Tin (IV) Fluoride or Stannic Fluoride Oxygen diflouride Copper (II) Iodide or Cupric Iodide Copper (I) Iodide or Cuprous Iodide Sulfur dioxide Strontium Sulfide Lithium Bromide Return to TOC 103 Naming Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 104 Naming Compounds • • • • Polyatomic ions are charged entities composed of several atoms bound together. They have special names and must be memorized. We will be using our Fat Daddy Chart to help us with naming the polyatomic compounds Those used often enough will be memorized just out of sheer practice Return to TOC Copyright © Cengage Learning. All rights reserved 105 Naming Compounds Names of Common Polyatomic Ions (page 130) Return to TOC Copyright © Cengage Learning. All rights reserved 106 Naming Compounds • Naming ionic compounds containing polyatomic ions follows rules similar to those for binary compounds. Ammonium acetate Return to TOC Copyright © Cengage Learning. All rights reserved 107 Naming Compounds Examples NaOH Sodium hydroxide Mg(NO3)2 Magnesium nitrate (NH4)2SO4 Ammonium sulfate FePO4 Iron(III) phosphate Return to TOC Copyright © Cengage Learning. All rights reserved 108 Naming Compounds Learning Check Select the correct name for each. A. Fe2S3 1) iron sulfide 2) iron(II) sulfide 3) iron(III) sulfide B. CuO 1) copper oxide 2) copper(I) oxide 3) copper(II) oxide 109 Return to TOC Naming Compounds Solution Select the correct name for each. A. Fe2S3 3) iron(III) sulfide Fe3+ S2– B. CuO 3) copper(II) oxide Cu2+ O2– 110 Return to TOC Naming Compounds Overall Strategy for Naming Chemical Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 111 Naming Compounds Exercise What is the name of the compound KClO3? a) b) c) d) potassium chlorite potassium chlorate potassium perchlorate potassium carbonate Return to TOC Copyright © Cengage Learning. All rights reserved 112 Naming Compounds Exercise Examine the following table of formulas and names. Which of the compounds are named correctly? a) b) c) d) I, II I, III, IV I, IV I only Formula Name I P2 O 5 Diphosphorus pentoxide II ClO2 Chlorine oxide III PbI4 Lead iodide IV CuSO4 Copper(I) sulfate Return to TOC Copyright © Cengage Learning. All rights reserved 113 Naming Compounds • Only Formula I is named correctly. • Formula II is chlorine dioxide. • Formula III is lead(IV) iodide. • Formula IV is copper(II) sulfate. Return to TOC Copyright © Cengage Learning. All rights reserved 114 Naming Compounds Acids • • • • • • Acids can be recognized by the hydrogen that appears first in the formula—HCl. Molecule with one or more H+ ions attached to an anion. Most lab acids are either: binary acids ( composed of Hydrogen and another element) or oxyacids (composed of Hydrogen, oxygen and a third element Copyright © Cengage Learning. All rights reserved Return to TOC 115 Naming Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 116 Naming Compounds Rules for Naming Acids • • If the anion does not contain oxygen, the acid is named with the prefix hydro– and the suffix –ic attached to the root name for the element. Examples: HCl Hydrochloric acid HCN Hydrocyanic acid H2S Hydrosulfuric acid Return to TOC Copyright © Cengage Learning. All rights reserved 117 Naming Compounds Acids That Do Not Contain Oxygen Return to TOC Copyright © Cengage Learning. All rights reserved 118 Naming Compounds Rules for Naming Acids • If the anion contains oxygen: The suffix –ic is added to the root name if the anion name ends in –ate. • Examples: HNO3 Nitric acid H2SO4 Sulfuric acid HC2H3O2 Acetic acid Return to TOC Copyright © Cengage Learning. All rights reserved 119 Naming Compounds Rules for Naming Acids • If the anion contains oxygen: The suffix –ous is added to the root name if the anion name ends in –ite. • Examples: HNO2 Nitrous acid H2SO3 Sulfurous acid HClO2 Chlorous acid Return to TOC Copyright © Cengage Learning. All rights reserved 120 Naming Compounds Some Oxygen-Containing Acids Return to TOC Copyright © Cengage Learning. All rights reserved 121 Naming Compounds Flowchart for Naming Acids Return to TOC Copyright © Cengage Learning. All rights reserved 122 Naming Compounds Exercise Which of the following compounds is named incorrectly? a) KNO3 b) TiO2 c) Sn(OH)4 d) PBr5 e) H2SO3 potassium nitrate titanium(II) oxide tin(IV) hydroxide phosphorus pentabromide sulfurous acid Return to TOC Copyright © Cengage Learning. All rights reserved 123 Naming Compounds • The correct answer is “b”. • The charge on oxygen is 2–. • Since there are two oxygen atoms, the overall charge is 4–. • Therefore, the charge on titanium must be 4+ (not 2+ as the Roman numeral indicates). Copyright © Cengage Learning. All rights reserved Return to TOC 124 Naming Compounds Examples • • • • • Sodium hydroxide NaOH Potassium carbonate K2CO3 Sulfuric acid H2SO4 Dinitrogen pentoxide N2O5 Cobalt(III) nitrate Co(NO3)3 Return to TOC Copyright © Cengage Learning. All rights reserved 125 Naming Compounds Exercise A compound has the formula XCl3 where X could represent a metal or nonmetal. What could the name of this compound be? a) b) c) d) phosphorus trichloride carbon monochloride tin(IV) chloride magnesium chloride Return to TOC Copyright © Cengage Learning. All rights reserved 126 Naming Compounds • • • • • Phosphorus trichloride. Carbon monochloride has the formula CCl. Tin(IV) chloride has the formula SnCl4. Magnesium chloride has the formula MgCl2. Phosphorus trichloride has the formula PCl3 and is therefore the correct answer Return to TOC Copyright © Cengage Learning. All rights reserved 127 Naming Compounds Lets Practice Some More! HF Hydroflouric acid Na2CO3 Sodium carbonate H2CO3 KMnO4 HClO4 H2S NaOH CuSO4 PbCrO4 Carbonic acid Potassium permanganate Perchloric acid Hyrdogen sulfuric acid Sodium hydroxide Copper (II) sulfate or Cupric sulfate Lead (II) chromate or Plubous chromate H2O Hydrooxic acid (no……just water) NH3 Nitrogen trihydride (no..just ammonia) Return to TOC 128 Naming Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 129 Naming Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 130 Naming Compounds Identifying Ionic Charges • Group A elements – use the periodic table to determine ionic charge * elements in same group have same ionic charge * Group 4A and Noble gases – almost never form ions • Group B elements – many have more than one ionic charge 131 Return to TOC Naming Compounds Identifying Ionic Charges http://wps.prenhall.com/wps/media/objects/476/488316/ch04.html Charge on cations corresponds to group #. Charge on anions is found by subtracting 8 by group number 132 the number 8 is used b/c it represents # of valence e- in Noble gases Return to TOC Naming Compounds Naming Cations and Anions • • • • • • • Potassium ion Copper (II) ion Chloride ion Oxide ion Ba2+ S2Au3+ • • • • • • Nitrite ion Hydroxide ion Phosphate ion SO42CrO42ClO32133 Return to TOC Naming Compounds Binary Ionic Compounds • Compounds composed of 2 different monatomic elements • To write binary formulas – write cation first, then anion *criss-cross charges to determine how many of each ion you need *use subscripts to denote number of ions ex: Ca2+ + Cl1CaCl2 Na1+ + Cl1- NaCl 134 Return to TOC Naming Compounds Ternary Ionic Compounds • Compounds containing at least one polyatomic ion; at least 3 different elements • To write ternary formulas: write cation first, then anion *criss-cross charges to determine how many of each ion you need *use subscripts to denote number of ions *must use parentheses around polyatomic if more than one is needed!!! ex: Na1+ + SO32Na2SO3 Mg2+ + OH1MgOH2] Mg(OH)2 [not same as 135 Return to TOC Naming Compounds Ionic Compounds • • • • • • NaNO3 CaSO4 (NH4)2O CuSO3 Fe(OH)3 NaF • • • • • • Lithium sulfide Iron (III) phosphide Magnesium fluoride Barium nitrate Aluminum hydroxide Potassium phosphate Practice making ionic compounds! 136 Return to TOC Naming Compounds Molecular Compounds • • • • • P2O5 N2O NO2 CBr4 CO2 • • • • • tetraiodine nonoxide sulfur hexafluoride nitrogen trioxide carbon tetrahydride phosphorus trifluoride 137 Return to TOC Naming Compounds Examples of Ionic Compounds with Two Elements Formula Ions Cation Anion NaCl Na+ Cl– sodium chloride K2S K+ S2– potassium sulfide MgO Mg2+ O2– magnesium oxide CaI2 Ca2+ I– calcium iodide Al2O3 Al3+ aluminum sulfide S2– Name 138 Return to TOC Naming Compounds Learning Check Write the formulas and names for compounds of the following ions: Br– S2− N3− Na+ Al3+ 139 Return to TOC Naming Compounds Solution Br− S2− N3− Na+ NaBr Na2S sodium bromide sodium sulfide Na3N sodium nitride Al3+ AlBr3 aluminum bromide AlN aluminum nitride Al2S3 aluminum sulfide 140 Return to TOC Naming Compounds Transition Metals Form Positive Ions Most transition metals and Group 4(14) metals, Form 2 or more positive ions Zn2+, Ag+, and Cd2+ form only one ion. 141 Return to TOC Naming Compounds Guide to Writing Formulas from the Name 142 Return to TOC Naming Compounds Writing Formulas Write a formula for potassium sulfide. STEP 1 Identify the cation and anion. potassium = K+ sulfide = S2− STEP 2 Balance the charges. K+ S2− K+ 2(1+) + 1(2–) = 0 STEP 3 Write the cation first. 2K+ and 1S2− = K2S1 = K2S 143 Return to TOC Naming Compounds Writing Formulas Write a formula for iron(III) chloride. STEP 1 Identify the cation and anion. iron (III) = Fe3+ (III = charge of 3+) chloride = Cl− STEP 2 Balance the charges. Fe3+ Cl− Cl− Cl− 1(3+) + 3(1–) = 0 STEP 3 Write the cation first. 1Fe3+ and 3Cl− = FeCl3 144 Return to TOC Naming Compounds Learning Check The correct formula for each of the following is: A. copper(I) nitride 1) CuN 2) CuN3 3) Cu3N B. lead(IV) oxide 1) PbO2 2) PbO 3) Pb2O4 145 Return to TOC Naming Compounds Solution The correct formula for each of the following is: A. copper(I) nitride 3) Cu3N 3Cu+ + N3– = 3(1+) + (3–) = 0 B. lead(IV) oxide 1) PbO2 Pb4+ + 2O2– = (4+) + 2(2–) = 0 146 Return to TOC Naming Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 147 Naming Compounds Percent Composition, Empirical Formulas, Molecular Formulas Return to TOC Naming Compounds Formula Masses and Molar masses: • Molecular mass or molecular weight are used instead of the term formula mass. • The formula mass of any compound is the sum of the average atomic masses of all of the atoms present in the formula Return to TOC 149 Naming Compounds Example of formula mass • H2O • 2 H atom weigh 1.0079 each • 1 O atom weighs 15.9994 each • 2 x 1.oo79 • +1x 15.9994 • 18.0153 formula mass for water Return to TOC 150 Naming Compounds Molar mass as a conversion factor • Moles x grams/mole = mass in grams • Mass in grams x 1 mol/grams = moles • Thus 2 conversions relate mass in grams to numbers of moles of a substance Return to TOC Copyright © Cengage Learning. All rights reserved 151 Naming Compounds Example • What is the molar mass of Barium nitrate Ba(NO3)2 • • • • Solution 1 mol Ba x 137.33 g/1 mol Ba = 137.33 g Ba 2 moles N x 14.0067 g/1mole N = 28.0134g N 6 moles O x 15.999g/1mol O = 95.9964g • Molar mass Ba(NO3)2 = 261.34 Return to TOC Copyright © Cengage Learning. All rights reserved 152 Naming Compounds Example • What is the mass in grams of 2.5 moles of oxygen gas (O2) • Solution • 80.0g Return to TOC Copyright © Cengage Learning. All rights reserved 153 Naming Compounds Return to TOC Percent Composition • Percent Composition – the percentage by mass of each element in a compound Percent = Percent composition of a compound or = molecule Part _______ Whole x 100% Mass of element in 1 mol ____________________ Mass of 1 mol x 100% Percent Composition Example: What is the percent composition of Potassium Permanganate (KMnO )? 4 Molar Mass of KMnO 4 K= 1(39.1) = 39.1 Mn = 1(54.9) = 54.9 O = 4(16.0) = 64.0 MM = 158 g Percent Composition Example: What is the percent composition of Potassium Permanganate (KMnO )? 4 Molar Mass of KMnO % K % Mn K= 1(39.10) = 39.1 Mn = 1(54.94) = 54.9 O = 4(16.00) = 64.0 MM = 158 % O 39.1 g K 158 g 54.9 g Mn 158 g 64.0 g O 158 g = 158 g 4 x 100 = x 100 = x 100 = 24.7 % 34.8 % 40.5 % Percent Composition Determine the percentage composition of sodium carbonate (Na CO )? 2 3 Molar Mass Na = 2(23.00) = 46.0 C = 1(12.01) = 12.0 O = 3(16.00) = 48.0 MM= 106 g Percent Composition % Na = % C = % O = 46.0 g 106 g 12.0 g 106 g 48.0 g 106 g x 100% = 43.4 % x 100% = 11.3 % x 100% = 45.3 % Percent Composition Determine the percentage composition of ethanol (C H OH)? 2 5 % C = 52.13%, % H = 13.15%, % O = 34.72% _______________________________________________ Determine the percentage composition of sodium oxalate (Na C O )? 2 2 4 % Na = 34.31%, % C = 17.93%, % O = 47.76% Percent Composition Calculate the mass of bromine in 50.0 g of Potassium bromide. 1. Molar Mass of KBr K = 1(39.10) = 39.10 Br =1(79.90) =79.90 MM = 119.0 2. 79.90 g ___________ = 0.6714 119.0 g 3. 0.6714 x 50.0g = 33.6 g Br Percent Composition Calculate the mass of nitrogen in 85.0 mg of the amino acid lysine, C H N O . 6 14 2 2 1. Molar Mass of C H N O 6 14 2 2 C = 6(12.01) = 72.06 H =14(1.01) = 14.14 N = 2(14.01) = 28.02 O = 2(16.00) = 32.00 MM = 146.2 2. 28.02 g ___________ = 0.192 146.2 g 3. 0.192 x 85.0 mg = 16.3 mg N Hydrates Hydrated salt – salt that has water molecules trapped within the crystal lattice Examples: CuSO •5H O , CuCl •2H O 4 2 2 2 Anhydrous salt – salt without water molecules Examples: CuCl 2 Can calculate the percentage of water in a hydrated salt. Percent Composition Calculate the percentage of water in sodium carbonate decahydrate, Na CO •10H O. 2 3 2 1. Molar Mass of Na CO •10H O 2 3 2 Na = 2(22.99) = 45.98 C = 1(12.01) = 12.01 H = 20(1.01) = 20.2 3. O = 13(16.00)= 208.00 180.2 g _______ MM = 286.2 2. 286.2 g Water H = 20(1.01) = 20.2 O = 10(16.00)= 160.00 MM = 180.2 or H = 2(1.01) = 2.02 O = 1(16.00) = 16.00 MM H2O = 18.02 So… 10 H O = 10(18.02) = 180.2 2 x 100%= 67.97 % Percent Composition Calculate the percentage of water in Aluminum bromide hexahydrate, AlBr •6H O. 3 2 1. Molar Mass of AlBr •6H O 3 2 Al = 1(26.98) = 26.98 Br = 3(79.90) = 239.7 H = 12(1.01) = 12.12 O = 6(16.00) = 96.00 MM = 374.8 2. Water H = 12(1.01) = 12.1 O = 6(16.00)= 96.00 MM = 108.1 or MM = 18.02 For 6 H2O = 6(18.02) = 108.2 3. 108.1 g _______ 374.8 g x 100%= 28.85 % Percent Composition If 125 grams of magnesium sulfate heptahydrate is completely dehydrated, how many grams of anhydrous magnesium sulfate will remain? MgSO 1. Molar Mass Mg = 1 x 24.31 = 24.31 g S = 1 x 32.06 = 32.06 g O = 4 x 16.00 = 64.00 g MM = 120.37 g 2. % MgSO 4 . 7 H O 2 4 120.4 g 246.5 g X 100 = 3. Grams anhydrous MgSO H = 2 x 1.01 = 2.02 g O = 1 x 16.00 = 16.00 g MM = 18.02 g MM H O = 2 g = 126.1 g 7 x 18.02 Total MM = 120.4 g + 126.1 g = 246.5 g 0.4884 x 125 = 48.84 % 4 61.1 g Percent Composition If 145 grams of copper (II) sulfate pentahydrate is completely dehydrated, how many grams of anhydrous copper sulfate will remain? CuSO . 5 H O 4 2 1. Molar Mass Cu = 1 x 63.55 = 63.55 g S = 1 x 32.06 = 32.06 g O = 4 x 16.00 = 64.00 g MM = 159.61 g 2. % CuSO 4 159.6 g 249.7 g X 100 = 3. Grams anhydrous CuSO H = 2 x 1.01 = 2.02 g O = 1 x 16.00 = 16.00 g MM = 18.02 g MM H O = 2 g = 90.1 g 5 x 18.02 Total MM = 159.6 g + 90.1 g = 249.7 g 0.6392 x 145 = 63.92 % 4 92.7 g Percent Composition A 5.0 gram sample of a hydrate of BaCl was heated, and only 4.3 grams of the 2 anhydrous salt remained. What percentage of water was in the hydrate? 1. Amount water lost 5.0 g hydrate 4.3 g anhydrous salt -0.7 g water 2. Percent of water 0.7 g water 5.0 g hydrate x 100 = 14 % Percent Composition A 7.5 gram sample of a hydrate of CuCl was heated, and only 5.3 grams of the 2 anhydrous salt remained. What percentage of water was in the hydrate? 1. Amount water lost 7.5 g hydrate 5.3 g anhydrous salt -2.2 g water 2. Percent of water 2.2 g water 7.5 g hydrate x 100 = 29 % Percent Composition A 5.0 gram sample of Cu(NO ) •nH O is heated, and 3.9 g of the anhydrous salt 32 remains. What is the value of n? 2 1. Amount water lost 5.0 g hydrate 3.9 g anhydrous salt -1.1 g water 3. Amount of water 0.22 x 18.02 = 2. Percent of water 1.1 g water 5.0 g hydrate x 100 = 22 % 4.0 Percent Composition A 7.5 gram sample of CuSO •nH O is heated, and 5.4 g of the anhydrous salt remains. 4 2 What is the value of n? 1. Amount water lost 7.5 g hydrate 5.4 g anhydrous salt -2.1 g water 3. Amount of water 0.28 x 18.02 = 2. Percent of water 2.1 g water 7.5 g hydrate x 100 = 28 % 5.0 Formulas Percent composition allow you to calculate the simplest in compound. ratio among the atoms found Empirical Formula – formula of a compound that expresses ratio of atoms. lowest whole number Molecular Formula – actual formula of a compound showing present the number of atoms Examples: C H 4 10 C H 2 5 - molecular C H O 6 12 6 - molecular - empirical CH O 2 - empirical Formulas Is H O an empirical or molecular formula? 2 2 Molecular, it can be reduced to HO HO = empirical formula Calculating Empirical Formula An oxide of aluminum is formed by the reaction of 4.151 g of aluminum with 3.692 g of oxygen. Calculate the empirical formula. 1. Determine the number of grams of each element in the compound. 4.151 g Al and 3.692 g O 2. Convert masses to moles. 4.151 g Al 1 mol Al = 0.1539 mol Al = 0.2308 mol O 26.98 g Al 3.692 g O 1 mol O 16.00 g O Calculating Empirical Formula An oxide of aluminum is formed by the reaction of 4.151 g of aluminum with 3.692 g of oxygen. Calculate the empirical formula. 3. Find ratio by dividing each element by smallest amount of moles. 0.1539 moles Al = 1.000 mol Al 0.1539 0.2308 moles O = 1.500 mol O 0.1539 4. Multiply by common factor to get whole number. (cannot have fractions of atoms in compounds) O = 1.500 x 2 = 3 Al = 1.000 x 2 = 2 therefore, Al O 2 3 Calculating Empirical Formula A 4.550 g sample of cobalt reacts with 5.475 g chlorine to form a binary compound. Determine the empirical formula for this compound. 4.550 g Co 1 mol Co = 0.07721 mol Co 58.93 g Co 5.475 g Cl 1 mol Cl = 0.1544 mol Cl 35.45 g Cl 0.07721 mol Co =1 0.07721 0.1544 mol Cl 0.07721 CoCl 2 =2 Calculating Empirical Formula When a 2.000 g sample of iron metal is heated in air, it reacts with oxygen to achieve a final mass of 2.573 g. Determine the empirical formula. Fe = 2.000 g 2.000 g Fe 1 mol Fe O = 2.573 g – 2.000 g = 0.5730 g = 0.03581 mol Fe 55.85 g Fe 0.573 g O 1 mol O = 0.03581 mol Fe 16.00 g 1:1 FeO Calculating Empirical Formula A sample of lead arsenate, an insecticide used against the potato beetle, contains 1.3813 g lead, 0.00672g of hydrogen, 0.4995 g of arsenic, and 0.4267 g of oxygen. Calculate the empirical formula for lead arsenate. 1.3813 g Pb 1 mol Pb = 0.006667 mol Pb 207.2 g Pb 0.00672 gH 1 mol H = 0.00667 mol H 1.008 g H 0.4995 g As 1 mol As = 0.006667 mol As 74.92 g As 0.4267g Fe 1 mol O 16.00 g O = 0.02667 mol O Calculating Empirical Formula A sample of lead arsenate, an insecticide used against the potato beetle, contains 1.3813 g lead, 0.00672g of hydrogen, 0.4995 g of arsenic, and 0.4267 g of oxygen. Calculate the empirical formula for lead arsenate. 0.006667 mol Pb 0.006667 0.00667 mol H 0.006667 0.006667 mol As 0.006667 0.02667 mol O 0.006667 = 1.000 mol Pb = 1.00 mol H = 1.000 mol As = 4.000 mol O PbHAsO 4 Calculating Empirical Formula The most common form of nylon (Nylon-6) is 63.38% carbon, 12.38% nitrogen, 9.80% hydrogen and 14.14% oxygen. Calculate the empirical formula for Nylon-6. Step 1: In 100.00g of Nylon-6 the masses of elements present are 63.38 g C, 12.38 g n, 9.80 g H, and 14.14 g O. Step 2: 63.38 g C 1 mol C = 5.302 mol C 9.80 g H 12.01 g C 12.38 g N 1 mol N 14.01 g N 1 mol H = 9.72 mol H 1.01 g H = 0.8837 mol N 14.14 g O 1 mol O 16.00 g O = 0.8832 mol O Calculating Empirical Formula The most common form of nylon (Nylon-6) is 63.38% carbon, 12.38% nitrogen, 9.80% hydrogen and 14.14% oxygen. Calculate the empirical formula for Nylon-6. Step 3: 5.302 mol C 0.8837 0.8837 mol N 0.8837 9.72 mol H 0.8837 0.8837 mol O 0.8837 = 6.000 mol C = 1.000 mol N = 11.0 mol H = 1.000 mol O 6:1:11:1 C NH O 6 11 Calculating molecular formula • It is not possible to determine the correct molecular formula unless the molecular mass of the substance has been determined • The relationship between the simplest formula and the molecular mass is: • (simple formula)x = molecular formula • Where x is a whole number multiple of the simple formula Calculating Molecular Formula A white powder is analyzed and found to have an empirical formula of P2O5. The compound has a molar mass of 283.88g. What is the compound’s molecular formula? Step 1: Molar Mass P = 2 x 30.97 g = 61.94g O = 5 x 16.00g = 80.00 g 141.94 g Step 2: Divide MM by Empirical Formula Mass 238.88 g 141.94g =2 Step 3: Multiply (P O ) = 2 52 P O 4 10 Calculating Molecular Formula A compound has an experimental molar mass of 78 g/mol. Its empirical formula is CH. What is its molecular formula? (CH) = 6 C = 12.01 g H = 1.01 g 13.01 g C H 6 6 78 g/mol 13.01 g/mol =6 Oxidation Numbers • Are used to indicate general distributions of electrons among bonded atoms. • Refer to handout for rules of oxidation numbers Ex find oxidation # of following: • UF6 • ClO3• Solution • • U = +6 Cl =+5 F = -1 O =-2