Chapter 5 MOORE.pptx.pdf

Because learning changes everything.® Chemistry: Atoms First Fifth Edition...

Because learning changes everything.® Chemistry: Atoms First Fifth Edition Julia Burdge and Jason Overby Chapter 5 Ionic and Covalent Compounds © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  Chapter 5 Ionic and Covalent Compounds 1 5.1 Compounds 5.2 Lewis Dot Symbols 5.3 Ionic Compounds and Bonding 5.4 Naming Ions and Ionic Compounds Formulas of Ionic Compounds Naming Ionic Compounds 5.5 Covalent Bonding and Molecules Molecules Molecular Formulas Empirical Formulas 5.6 Naming Molecular Compounds Specifying Number of Atoms Compounds Containing Hydrogen Organic Compounds © McGraw Hill LLC 2  Chapter 5 Ionic and Covalent Compounds 2 5.7 Covalent Bonding in Ionic Species Polyatomic Ions Oxoacids Hydrates Familiar Inorganic Compounds 5.8 Molecular and Formula Masses 5.9 Percent Composition of Compounds 5.10 Molar Mass Interconverting Mass, Moles, and Number of Particles Determination of Empirical Formula and Molecular Formula from Percent Composition © McGraw Hill LLC 3  5.1 Compounds A compound is a substance composed of two or more elements combined in a specific ratio and held together by chemical bonds. Familiar examples of compounds water and salt (sodium chloride). © McGraw Hill LLC H.S. Photos/Alamy Stock Photo 4  5.2 Lewis Dot Symbols When atoms form compounds, it is their valence electrons that actually interact. A Lewis dot symbol consists of the element’s symbol with dots. Each dot represents a valence electron. Access the text alternative for slide images. © McGraw Hill LLC 5  Lewis Dot Symbols 1 Lewis dot symbols of the main group elements. © McGraw Hill LLC 6  Lewis Dot Symbols 2 For main group metals such as Na, the number of dots is the number of electrons that are lost. For nonmetals in the second period, the number of unpaired dots is the number of bonds the atom can form. Access the text alternative for slide images. © McGraw Hill LLC 7  Lewis Dot Symbols 3 Ions may also be represented by Lewis dot symbols. © McGraw Hill LLC 8  Quick Check Write Lewis dot symbols for (a) fluoride ion (b) potassium ion and (c) sulfide ion © McGraw Hill LLC 9  5.3 Ionic Compounds and Bonding Ionic bonding refers to the electrostatic attraction that holds oppositely charged ions together in an ionic compound. The attraction between the cation and anion draws them together to form NaCl Access the text alternative for slide images. © McGraw Hill LLC 10  Ionic Compounds and Bonding 1 The resulting electrically neutral compound, sodium chloride, is represented with the chemical formula NaCl. The chemical formula, or simply formula, of an ionic compound denotes the constituent elements and the ratio in which they combine. © McGraw Hill LLC 11  Ionic Compounds and Bonding 2 A three-dimensional array of oppositely charged ions is called a lattice. Lattice energy is the amount of energy required to convert a mole of ionic solid to its constituent ions in the gas phase. The formation of ionic bonds releases a large amount of energy. Access the text alternative for slide images. © McGraw Hill LLC 12  Ionic Compounds and Bonding 3 The magnitude of lattice energy is a measure of an ionic compound’s stability. Lattice energy depends on the magnitudes of the charge and on the distance between them. Access the text alternative for slide images. © McGraw Hill LLC 13  Ionic Compounds and Bonding 4 TABLE 5.1 Lattice Energies of Selected Ionic Compounds Compound Lattice Energy (kJ/mol) Melting Point (°C) LiF 1017 845 LiCl 860 610 LiBr 787 550 LiI 732 450 NaCl 788 801 NaBr 736 750 NaI 686 662 KCl 699 772 KBr 689 735 KI 632 680 MgCl2 2527 714 Na2O 2570 Sub* MgO 3890 2800 ScN 7547 > 3000 *Na2O sublimes at 1275°C. © McGraw Hill LLC 14  Ionic Compounds and Bonding 5 The magnitude of lattice energy is a measure of an ionic compound’s stability. Lattice energy depends on the magnitudes of the charge and on the distance between them. © McGraw Hill LLC 15  Ionic Compounds and Bonding 6 © McGraw Hill LLC 16  Quick Check 5.2 Arrange MgO, CaO, and SrO in order of increasing lattice energy. © McGraw Hill LLC 17  5.4 Naming Ions and Ionic Compounds A monatomic cation is named by adding the word ion to the name of the element. A monatomic anion is named by changing the ending of the element’s name to –ide. Some metals can form cations of more than one possible charge. © McGraw Hill LLC 18  Naming Ions and Ionic Compounds 1 Cations © McGraw Hill LLC 19  Naming Ions and Ionic Compounds 2 Anions © McGraw Hill LLC 20  Formulas of Ionic Compounds 1 Ionic compounds are electronically neutral. In order for ionic compounds to be electronically neutral, the sum of the charges on the cation and anion in each formula must be zero. Aluminum oxide: Sum of charges: © McGraw Hill LLC 21  Formulas of Ionic Compounds 2 © McGraw Hill LLC 22  Naming Ions and Ionic Compounds To name ionic compounds: 1. Name the cation. omit the word ion. use a Roman numeral if the cation can have more than one charge. 2. Name the anion. omit the word ion. Examples: NaBr sodium bromide FeCl2 iron(II) chloride FeCl3 iron(III) chloride © McGraw Hill LLC 23  Quick Check 5.3 Name the following ionic compounds: (a) CaO, (b) Mg3N2, and (c) Fe2S3. © McGraw Hill LLC 24  Worked Example 5.4 Deduce the formulas of the following ionic compounds: (a) mercury(II) chloride, (b) lead(II) bromide, and (c) potassium nitride. © McGraw Hill LLC 25  5.5 Covalent Bonding and Molecules When compounds form between 2 non metal atoms, electrons are not transferred from one element to another but instead are shared in order to give each atom a noble gas configuration. This approach is known as the Lewis theory of bonding, named for its proponent, Gilbert Lewis. Lewis theory depicts bond formation in H2 as. This type of arrangement, where two atoms share a pair of electrons, is known as covalent bonding, and the shared pair of electrons constitutes a covalent bond. Access the text alternative for slide images. © McGraw Hill LLC 26  Covalent Bonding and Molecules 1 A molecule is a combination of at least two atoms in a specific arrangement held together by chemical forces called covalent bonds A molecule may be an element or a compound. Different samples of a given compound always contain the same elements in the same ratio. This is known as the law of definite proportions. © McGraw Hill LLC 27  Covalent Bonding and Molecules 2 If two elements can form two or more different compounds, the law of multiple proportions tells us that the ratio of masses of one element that combine with a fixed mass of the other element can be expressed in small whole numbers. In addition to carbon dioxide, carbon also combines with oxygen to form carbon monoxide. © McGraw Hill LLC 28  Covalent Bonding and Molecules 3 The mass ratio of oxygen to carbon in carbon dioxide is , and the ratio of oxygen to carbon in carbon monoxide is The ratio of two such mass ratios can be expressed as small whole numbers. Access the text alternative for slide images. © McGraw Hill LLC 29  Covalent Bonding and Molecules 4 Diatomic molecules contain two atoms and may be either heteronuclear or homonuclear. Polyatomic molecules contain more than two atoms. © McGraw Hill LLC 30  Empirical Formulas Molecular substances can also be represented using empirical formulas, the whole-number ratio of elements. While, the molecular formulas tell us the actual number of atoms (the true formula), the empirical formula gives the simplest formula. Molecular formula: N2H4 Empirical formula: NH2 The molecular and empirical formulas are often the same. © McGraw Hill LLC 31  Covalent Bonding and Molecules TABLE 5.4 Molecular and Empirical Formulas © McGraw Hill LLC 32  Worked Example 5.6 1 Write the empirical formulas for the following molecules: (a) glucose (C6H12O6), a substance known as blood sugar; (b) adenine (C5H5N5), also known as vitamin B4; and (c) nitrous oxide (N2O), a gas that is used as an anesthetic (“laughing gas”) and as an aerosol propellant for whipped cream. © McGraw Hill LLC 33  5.6 Naming Molecular Compounds Remember that binary molecular compounds are substances that consist of just two different elements. Nomenclature: 1. Name the first element that appears in the formula. 2. Name the second element that appears in the formula, changing its ending to –ide. Examples: HCl hydrogen chloride HI hydrogen iodide © McGraw Hill LLC 34  Naming Molecular Compounds 1 Greek prefixes are used to denote the number of atoms of each element present. Table 5.5 Greek Prefixes Prefix Meaning Prefix Meaning Mono– 1 Hexa– 6 Di– 2 Hepta– 7 Tri– 3 Octa– 8 Tetra– 4 Nona– 9 Penta– 5 Deca– 10 © McGraw Hill LLC 35  Naming Molecular Compounds 2 TABLE 5.6 Some Compounds Named Using Greek Prefixes Compound Name Compound Name CO Carbon monoxide S O3 Sulfur trioxide C O2 Carbon dioxide N O2 Nitrogen dioxide S O2 Sulfur dioxide N2O5 Dinitrogen pentoxide The prefix mono- is generally omitted for the first element. For ease of pronunciation, we usually eliminate the last letter of a prefix that ends in “o” or “a” when naming an oxide. Example: N2O5 is dinitrogen pentoxide not dinitrogen pentaoxide © McGraw Hill LLC 36  Quick Check 5.7 Name the following binary molecular compounds: (a) NF3 and (b) N2O4. © McGraw Hill LLC 37  Quick Check 5.8 Write the chemical formulas for the following binary molecular compounds: (a) sulfur tetrafluoride and (b) tetraphosphorus decasulfide. © McGraw Hill LLC 38  Compounds Containing Hydrogen 1 The names of molecular compounds containing hydrogen do not usually conform to the systematic nomenclature guidelines. Many are called by the common, nonsystematic names or by names that do not indicate explicitly the number of H atoms present. Examples: B2H6 Diborane SiH4 Silane NH3 Ammonia PH3 Phosphine H2O Water H2S Hydrogen sulfide © McGraw Hill LLC 39  Compounds Containing Hydrogen 2 One definition of an acid is a substance that produces hydrogen ions when dissolved in water. HCl is an example of a binary compound that is an acid when dissolved in water. To name these types of acids: 1) remove the –gen ending from hydrogen. 2) change the –ide ending on the second element to –ic. hydrogen chloride → hydrochloric acid © McGraw Hill LLC 40  Compounds Containing Hydrogen 3 A compound must contain at least one ionizable hydrogen atom to be an acid upon dissolving. TABLE 5.7 Some Simple Acids Formula Binary Compound Name Acid Name HF Hydrogen fluoride Hydrofluoric acid HCl Hydrogen chloride Hydrochloric acid HBr Hydrogen bromide Hydrobromic acid HI Hydrogen iodide Hydroiodic acid HCN* Hydrogen cyanide Hydrocyanic acid *Although HCN is not a binary compound, it is included in this table because it is similar chemically to HF, HCl, HBr, and HI. © McGraw Hill LLC 41  Organic Compounds 1 Our nomenclature discussion so far has focused on inorganic compounds, generally defined as those without carbon. Organic compounds contain carbon and hydrogen, sometimes in combination with other atoms. Hydrocarbons contain only carbon and hydrogen. The simplest hydrocarbons are called alkanes. © McGraw Hill LLC 42  Organic Compounds 2 TABLE 5.8 Formulas, Names, and Models of Some Simple Alkanes © McGraw Hill LLC 43  Organic Compounds 3 TABLE 5.8 Formulas, Names, and Models of Some Simple Alkanes © McGraw Hill LLC 44  Organic Compounds 4 Many organic compounds contain groups of atoms known as functional groups, which often determine a molecule’s reactivity. TABLE 5.9 Organic Functional Groups © McGraw Hill LLC 45  5.7 Covalent Bonding in Ionic Species Polyatomic ions consist of a combination of two or more atoms. Formulas are determined following the same rule as for ionic compounds containing only monatomic ions: ions must combine in a ratio that give a neutral formula overall. Calcium phosphate: Sum of charges: © McGraw Hill LLC 46  Polyatomic Ions 1 TABLE 5.10 Common Polyatomic Ions Access the text alternative for slide images. © McGraw Hill LLC 47  Polyatomic Ions 2 TABLE 5.10 Common Polyatomic Ions Access the text alternative for slide images. © McGraw Hill LLC 48  Quick check 5.9 1 Name the following ionic compounds: (b) Al(OH)3, and (c) Hg2O. © McGraw Hill LLC 49  Worked Example 5.9 2 Oxoanions are polyatomic anions that contain one or more oxygen atoms and one atom (the “central atom”) of another element. Starting with the oxoanions that end in –ate, we can name these ions as follows: 1. The ion with one more O atom than the –ate ion is called the per…ate ion. Thus, is the chlorate ion, so is the perchlorate ion. 2. The ion with one less O atom than the –ate ion is called the –ite ion. Thus, is the chlorite ion. 3. The ion with two fewer O atom than the –ate ion is called the hypo…ite ion. Thus, is the hypochlorite ion. At minimum, memorize the oxoanions that end in –ate so you can apply these guidelines when necessary. © McGraw Hill LLC 50  Polyatomic Ions 3 © McGraw Hill LLC 51  Oxoacids 1 Oxoacids, when dissolved in water, produce hydrogen ions and the corresponding oxoanions. An acid based on an –ate ion is called.........ic acid. HClO3 is chloric acid. An acid based on an –ite ion is called.........ous acid. HClO2 is chlorous acid. Prefixes in oxoanion names are retained in naming the oxoacids. HClO4 is perchloric acid. HClO is hypochlorous acid. © McGraw Hill LLC 52  Oxoacids 2 Oxoacids, can be monoprotic (one ionizable hydrogen) or polyprotic (more than one ionizable hydrogen) The names of the anions indicate the number of the remaining hydrogens. © McGraw Hill LLC 53  Quick Check 5.10 1 Name the following species: (a) (b) (c) H2CO3, © McGraw Hill LLC 54  Hydrates 1 A hydrate is a compound that has a specific number of water molecules within its solid structure. For example, in its normal state, copper(II) sulfate has five water molecules associated with it. Systematic name: copper(II) sulfate pentahydrate Formula: Some other hydrates are © McGraw Hill LLC 55  Hydrates 2 When the water molecules are driven off by heating, the resulting compound, Cu(SO)4, is sometimes called anhydrous copper(II) sulfate. Anhydrous means the compound no longer has water molecules associated with it. Cu(SO)4 is white © McGraw Hill LLC Charles D. Winters/Timeframe Photography/McGraw Hill 56  5.8 Molecular and Formula Mass The molecular mass is the mass in atomic mass units (amu) of an individual molecule. To calculate molecular mass, multiply the atomic mass for each element in a molecule by the number of atoms of that element and then total the masses. Because the atomic masses on the periodic table are average atomic masses, the result of such a determination is an average molecular mass, sometimes referred to as the molecular weight. © McGraw Hill LLC 57  Molecular and Formula Mass Although an ionic compound does not have a molecular mass, we can use its empirical formula to determine its formula mass (the mass of a “formula unit”), sometimes called the formula weight. The process is the same: To calculate formula mass, multiply the atomic mass for each element in a formula unit by the number of atoms of that element and then total the masses. © McGraw Hill LLC 58  Quick Check 5.12 1 Calculate the molecular mass or the formula mass, as appropriate, for each of the following corresponds: (a) propane, C3H8, (b) lithium hydroxide, LiOH, and (c) barium acetate, © McGraw Hill LLC 59  5.9 Percent Composition of Compounds A list of the percent by mass of each element in a compound is known as the compound’s percent composition by mass. where n is the number of atoms of the element in a molecule or formula unit of the compound. © McGraw Hill LLC 60  Percent Composition of Compounds 1 For a molecule of H2O2: © McGraw Hill LLC 61  Percent Composition of Compounds 2 We could also have used the empirical formula of hydrogen peroxide (HO) for the calculation. In this case, we could have used the empirical formula mass, the mass in amu of one empirical formula, in place of the molecular formula. The empirical formula mass of H2O2 (the mass of HO) is 17.01 amu. © McGraw Hill LLC 62  Quick Check 5.13 1 Lithium carbonate, Li2CO3, was the first “mood-stabilizing” drug approved by the FDA for the treatment of mania and manic-depressive illness, also known as bipolar disorder. Calculate the percent composition by mass of lithium carbonate. © McGraw Hill LLC 63  5.10 Molar Mass The molar mass (M) of a substance is the mass in grams of one mole of the substance. The molar mass of an element is numerically equal to its atomic mass. 1 mol C = 12.01 g 1 C atom = 12.01 amu The molar mass of a compound is the sum of molar masses of the elements it contains. The molar mass of a compound is the sum of molar masses of the elements it contains. © McGraw Hill LLC 64  Molar Mass When expressing the molar mass of elements such as oxygen and hydrogen, we have to be careful to specify which form of the element we mean. For instance, the element oxygen exists predominantly as O2. But we might also mean atomic oxygen (O). We must consider the context to tell which form of the element, O2 or O, is intended. Context Oxygen means Molar mass How many moles of oxygen react with 2 moles of O2 32.00 g hydrogen to produce water? How many moles of oxygen are there in 1 mole of O 16.00 g water? Air is approximately 21 percent oxygen. O2 32.00 g Many organic compounds contain oxygen. O 16.00 g © McGraw Hill LLC 65  Interconverting Mass, Moles, and Numbers of Particles © McGraw Hill LLC 66  Quick Check 5.14 Determine (a) the number of moles of CO2 in 10.00 g of carbon dioxide and (b) the mass of 0.905 mole of sodium chloride. © McGraw Hill LLC 67  Quick Check 5.15 1 (a) Determine the number of water molecules and the numbers of H and O atoms in 3.26 g of water. (b) Determine the mass of © McGraw Hill LLC 68  Determination of Empirical Formula and Molecular Formula from Percent Composition Using the concepts of the mole and molar mass, we can now use an experimentally determined percent composition to determine the empirical and/or molecular formula. The empirical formula gives only the ratio of atoms in a molecule, so there may be multiple compounds with the same empirical formula. If we know the approximate molar mass of the compound, we can determine the molecular formula by dividing the molar mass by the empirical formula mass. We then multiply the empirical formula by this number to obtain the molecular formula. © McGraw Hill LLC 69  Worked Example 5.16 1 Determine the empirical formula of a compound that is 30.45 percent nitrogen and 69.55 percent oxygen by mass. Given that the molar mass of the compound is approximately 92 g/mol, determine the molecular formula of the compound. Strategy Assume a 100-g sample so that the mass percentages of nitrogen and oxygen given in the problem statement correspond to the masses of N and O in the compound. Then, using the appropriate molar masses, convert the grams of each element to moles. Use the resulting numbers as subscripts in the empirical formula, reducing them to the lowest possible whole numbers for the final answer. To calculate the molecular formula, first divide the molar mass given in the problem statement by the empirical formula mass. Then, multiply the subscripts in the empirical formula by the resulting number to obtain the subscripts in the molecular formula. The molar masses of N and O are 14.01 and 16.00 g/mol, respectively. One hundred grams of a compound that is 30.45 percent nitrogen and 69.35 percent oxygen by contains 30.45 g N and 69.55 g O. © McGraw Hill LLC 70  Worked Example 5.16 2 Solution This gives a formula of N2.173O4.347. Dividing both subscripts by the smaller of the two to get the smallest possible whole numbers gives an empirical formula of NO2. Finally, dividing the approximate molar mass (92 g/mol) by the empirical formula mass Then, multiplying both subscripts in the empirical formula by 2 gives the molecular formula, N2O4. Think About It Use the method described in Worked Example 5.13 to calculate the percent composition of the molecular formula N2O4 and verify that it is the same as that given in this problem. © McGraw Hill LLC 71  Quick Check 5.16 © McGraw Hill LLC