无机化学课件：05 06 Ionic Covalent Bond

1、Chemistry: Atoms FirstJulia Burdge & Jason OverbyChapter 5Ionic and Covalent CompoundsIonic and Covalent Compounds5.1Compounds5.2Lewis Dot Symbols5.3Ionic Compounds and Bonding5.4Naming Ions and Ionic CompoundsFormulas of Ionic CompoundsNaming Ionic Compounds5.5Covalent Bonding and MoleculesMolecule

2、sMolecular FormulasEmpirical Formulas5.6Naming Molecular CompoundsSpecifying Numbers of AtomsCompounds Containing HydrogenOrganic Compounds55.7 Covalent Bonding in Ionic SpeciesPolyatomic IonsOxoacidsHydratesFamiliar Inorganic Compounds5.8 Molecular and Formula Masses5.9 Percent Composition of Compo

3、unds5.10 Molar MassInterconverting Mass, Moles, and Number of ParticlesDetermination of Empirical Formula and Molecular Formula from Percent CompositionIonic and Covalent Compounds5Types of Chemical Bonding1. Metal with nonmetal:electron transfer and ionic bonding2. Nonmetal with nonmetal:electron s

4、haring and covalent bonding3. Metal with metal:electron pooling and metallic bondingThe three models of chemical bonding.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 are water and salt (sodi

5、um chloride). Compounds5.1When atoms form compounds, it is their valence electrons that actually interact.A Lewis dot symbol consists of the elements symbol surround by dots.Each dot represents a valence electron.Boron1s22s22p13 valence electronsBLewis dot symbol for boronBBBother reasonable Lewis d

6、ot symbols for boronLewis Dot Symbols5.2Atoms combine in order to achieve a more stable electron configuration. Maximum stability results when a chemical species is isoelectronic with a noble gas.Na: 1s22s22p63s1Na+: 1s22s22p610 electrons total, isoelectronic with NeCl: 1s22s22p63s23p5Cl: 1s22s22p63

7、s23p618 electrons total, isoelectronic with ArLewis Dot SymbolsLewis Dot SymbolsLewis dot symbols of the main group elements. Lewis Dot SymbolsDots are not paired until absolutely necessary.NaOFor main group metals such as Na, the number of dots is the number of electrons that are lost.For nonmetals

8、 in the second period, the number of unpaired dots is the number of bonds the atom can form.B1s22s22p1C1s22s22p2N1s22s22p35 valence electrons; first pair formed in the Lewis dot symbolLewis Dot SymbolsIons may also be represented by Lewis dot symbols.NaNa 1s22s22p63s1Na+ 1s22s22p6Na+OO 1s22s22p4O2 1

9、s22s22p6O2Core electrons not represented in the Lewis dot symbolValence electron lost in the formation of the Na+ ion.Remember the charge Worked Example 5.1Strategy Starting with the Lewis dot symbols for each element, add dots (for anions) or remove dots (for cations) as needed to achieve the corre

10、ct charge on each ion. Dont forget to include the appropriate charge on the Lewis dot symbol.Write Lewis dot symbols for (a) fluoride ion (F-), (b) potassium ion (K+), and (c) sulfide ion (S2-).Solution (a) (b) K+(c)Think About It For ions that are isoelectronic with noble gases, cations should have

11、 no dots remaining around the element symbol, whereas anions should have eight dots around the element symbol. Note, too, that for anions, we put square brackets around the Lewis dot symbol and place the negative charge outside the brackets. Because the symbol for a common cation such as the potassi

12、um ion has no remaining dots, square brackets are not necessary.Ionic bonding refers to the electrostatic attraction that holds oppositely charged ions together in an ionic compound.Na Na+e+ClCleNa Na+ClClThe attraction between the cation and anion draws them together to form NaClIonic Compounds and

13、 Bonding5.3Ionic Compounds and BondingThe 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.Ionic Compounds and Bon

14、dingA 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.+NaCl(s) Na+(g) + Cl(g)Hlattice = +788 kJ/molIonic Compounds and BondingThe magnitude of lattice ene

15、rgy is a measure of an ionic compounds stability.Lattice energy depends on the magnitudes of the charge and on the distance between them.dQ1Q2Q = amount of charged = distance of separationIonic Compounds and BondingIonic Compounds and BondingThe magnitude of lattice energy is a measure of an ionic c

16、ompounds stability.Lattice energy depends on the magnitudes of the charge and on the distance between them.Ionic Compounds and Bonding Worked Example 5.2Strategy Consider the charges on the ions and the distances between them. Apply Coulombs law to determine the relative lattice energies. All three

17、compounds contain O2- and all three cations are +2. Recalling that lattice energy increases as the distance between ions decreases, we need only consider the radii of the cations as all three contain the same anion. From Figure 4.13, the ionic radii are 0.72 (Mg2+), 1.00 (Ca2+), and 1.18 (Sr2+).Arra

18、nge MgO, CaO, and SrO in order of increasing lattice energy.Solution MgO has the smallest distance between ions, whereas SrO has the largest distance between ions. Therefore, in order of increase lattice energy: SrO CaO MgO.Think About It Mg, Ca, and Sr are all Group 2A metals, so we could have pred

19、icted this result without knowing their radii. Recall that ionic radii increase as we move down a column in the periodic table, and charges that are farther apart are more easily separated (meaning the lattice energy will be smaller.) The lattice energies of SrO, CaO, and MgO are 3217, 3414, and 389

20、0 kJ/mol, respectively.Electrostatic forcesand the reason ionic compounds crack.Electrical conductance and ion mobility.Solid ionic compoundMolten ionic compoundIonic compound dissolved in waterA monatomic ion is named by changing the ending of the elements name to ide.Cl is chlorideO2 is oxideSome

21、metals can form cations of more than one possible charge.Fe2+ : ferrous ion Fe(II)Fe3+ : ferric ion Fe(III)Mn2+ : manganese(II) ionMn3+ : manganese(III) ionMn4+ : manganese(IV) ionNaming Ions and Ionic Compounds5.4Naming Ions and Ionic CompoundsNaming Ions and Ionic CompoundsTo name ionic compounds:

22、1) Name the cation omit the word ionuse a Roman numeral if the cation can have more than one charge2) Name the anionomit the word ionExamples:NaCN sodium cyanideFeCl2 iron(II) chlorideFeCl3iron(III) chloride Worked Example 5.3Strategy Begin by identifying the cation and anion in each compound, and t

23、hen combine the names for each, eliminating the word ion.Name the following ionic compounds: (a) CaO, (b) Mg3N2, and (c) Fe2S3.Solution (a) CaO is calcium oxide.(b) Mg3N2 is magnesium nitride.(c) Fe2S3 is iron(III) sulfide.Think About It Be careful not to confuse the subscript in the formula with th

24、e charge in the metal ion. In part (c), for example, the subscript on Fe is 2, but this is an iron(III) compound. Worked Example 5.4Strategy Identify the ions in each compound, and determine their ratios of combination using the charges on the cation and anion in each.Deduce the formulas of the foll

25、owing ionic compounds: (a) mercury(II) chloride, (b) lead(II) bromide, and (c) potassium nitride.Solution (a) Mercury(II) chloride is a combination of Hg2+ and Cl-. To produce a neutral compound, these two ions must combine in a 1:2 ratio HgCl2.(b) Lead(II) bromide is a combination of Pb2+ and Cl-.

26、These ions combine in a 1:2 ratio to give PbBr2.(c) Potassium nitride is a combination of K+ and N3-. These ions combine in a 3:1 ratio to give K3N.Think About It Make sure that the charges sum to zero in each compound formula. In part (a), for example, Hg2+ + 2Cl- = (+2) + 2(-1) = 0; in part (b), (

27、+2) + 2(-1) = 0; and in part (c), 3(+1) + (-3) = 0.When compounds form between elements with similar properties, 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

28、, named for its proponent, Gilbert Lewis.Lewis theory depicts bond formation in H2 asH + H H:HThis 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.Covalent Bonding and Molecules5.5Diatomic mole

29、cules contain two atoms and may be either heteronuclear or homonuclear.Polyatomic molecules contain more than two atoms.Covalent Bonding and MoleculesCovalent Bonding and MoleculesA chemical formula denotes the composition of the substance.A molecular formula shows the exact number of atoms of each

30、element in a molecule.Some elements have two or more distinct forms known as allotropes.For example, oxygen (O2) and ozone (O3) are allotropes of oxygen.A structural formula shows not only the elemental composition, but also the general arrangements.Covalent Bonding and Molecules Worked Example 5.5S

31、trategy Refer to the labels on the atoms (or see Table 5.3). There are two carbon atoms, six hydrogen atoms, and one oxygen atom, so the subscript on C will be 2 and the subscript on H will be 6, and there will be no subscript on O.Write the molecular formula of ethanol based on its ball-and-stick m

32、odel, shown here.Solution C2H6OThink About It Often the molecular formula for a compound such as ethanol (consisting of carbon, hydrogen, and oxygen) is written so that the formula more closely resembles the actual arrangement of atoms in the molecule. Thus, the molecular formula for ethanol is comm

33、only written as C2H5OH.Covalent Bonding and MoleculesRemember 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 i

34、de. Examples:HCl hydrogen chlorideHIhydrogen iodideNaming Molecular Compounds5.6Greek prefixes are used to denote the number of atoms of each element present.Naming Molecular CompoundsThe prefix mono- is generally omitted for the first element.For ease of pronunciation, we usually eliminate the last

35、 letter of a prefix that ends in “o” or “a” when naming an oxide.Example: N2O5 is dinitrogen pentoxide not dinitrogen pentaoxideNaming Molecular Compounds Worked Example 5.7Strategy Each compound will be named using the systematic nomenclature including, where necessary, appropriate Greek prefixes.N

36、ame the following binary molecular compounds: (a) NF3 and (b) N2O4.Solution (a) nitrogen trifluoride(b) dinitrogen tetroxideThink About It Make sure that the prefixes match the subscripts in the molecular formulas and that the word oxide is not preceded immediately by an “a” or an “o”. Worked Exampl

37、e 5.8Strategy The formula for each compound will be deduced using the systematic nomenclature guidelines.Write the chemical formulas for the following binary molecular compounds: (a) sulfur tetrafluoride and (b) tetraphosphorus decasulfide.Solution (a) SF4(b) P4S10Think About It Double-check that th

38、e subscripts in the formulas match the prefixes in the compound names: (a) 4 = tetra and (b) 4 = tetra and 10 = deca.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 th

39、at do not indicate explicitly the number of H atoms present.Examples:B2H6DiboraneSiH4SilaneNH3AmmoniaPH3PhosphineH2OWaterH2SHydrogen sulfideCompounds Containing HydrogenCompounds Containing HydrogenOne definition of an acid is a substance that produces hydrogen ions (H+) when dissolved in water.HCl

40、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 hydrogen2) change the ide ending on the second element to ic.hydrogen chloride hydrochloric acidCompounds Containing HydrogenA compound must contain at least one ioni

41、zable hydrogen atom to be an acid upon dissolving.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:Co

42、valent Bonding in Ionic Species5.7Ca2+PO43 Ca3(PO4)2Sum of charges:3(+2) + 2(3) = 0Covalent Bonding in Ionic SpeciesCovalent Bonding in Ionic Species Worked Example 5.9Strategy Begin by identifying the cation and anion in each compound, and then combine the names for each, eliminating the word ion.N

43、ame the following ionic compounds: (a) Fe2(SO4)3, (b) Al(OH)3, and (c) Hg2O.Solution (a) Fe2(SO4)3 is iron(III) sulfate.(b) Al(OH)3 is aluminum hydroxide.(c) Hg2O is mercury(I) oxide.Think About It Be careful not to confuse the subscript in the formula with the charge in the metal ion. In part (a),

44、for example, the subscript on Fe is 2, but this is an iron(III) compound.Covalent Bonding in Ionic SpeciesOxoanions 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

45、follows:The ion with one more O atom than the ate ion is called the perate ion. Thus, ClO3- is the chlorate ion, so ClO4- is the perchlorate ion.The ion with one less O atom than the ate ion is called the ite ion. Thus, ClO2- is the chlorite ion.The ion with two fewer O atom than the ate ion is call

46、ed the hypoite ion. Thus, ClO- is the hypochlorite ion.At minimum, memorize the oxoanions that end in ate so you can apply these guidelines when necessary.Covalent Bonding in Ionic SpeciesperchlorateClO4-chlorateClO3-chloriteClO2-hypochloriteClO-nitrateNO3-nitriteNO2-phosphatePO43-phosphitePO33-sulf

47、ate SO42-sulfiteSO32- Worked Example 5.10Strategy Each species is either an oxoanion or an oxoacid. Identify the “reference oxidation” (the one with the ate ending) for each, and apply the rules to determine appropriate names.Name the following species: (a) BrO4-, (b) HCO3-, and (c) H2CO3.Solution (

48、a) BrO4- has one more O atom than the bromate ion (BrO3-), so BrO4- is the perbromate ion.(b) CO32- is the carbonate ion. Because HCO3- has one ionizable hydrogen atom, it is called the hydrogen carbonate ion.(c) With two ionizable hydrogen atoms and no charge on the compound, H2CO3 is carbonic acid

49、.Think About It Make sure that the charges sum to zero in each compound formula. In part (a), for example, Hg2+ + 2Cl- = (+2) + 2(-1) = 0; in part (b), (+2) + 2(-1) = 0; and in part (c), 3(+1) + (-3) = 0.Think About It Remembering all these names and formulas is greatly facilitated by memorizing the

50、 common ions that end in ate.chlorateClO3-nitrateNO3-iodateIO3-carbonateCO32-bromateBrO3-oxalateC2O42-sulfateSO42-chromateCrO42-phosphatePO43-permanganateMnO4- Worked Example 5.11Strategy The ous ending in the name of an acid indicates that the acid is derived from an oxoanion ending in ite. The oxo

51、anion must be sulfite, SO32-, so add enough hydrogen ions to make a neutral formula.Determine the formula of sulfurous acid.Solution The formula of sulfurous acid is H2SO3.Think About It Remembering all these names and formulas is greatly facilitated by memorizing the common ions that end in -ate.Hy

52、dratesA 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 pentahydrateFormula: Cu(SO)4 5H2OSome other hydrates areBaCl2 2H

53、2OLiCl H2OMgSO4 7H2OSr(NO3)2 4H2OHydratesWhen 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.Familiar Inorganic CompoundsChapter Summary: Ke

54、y Points5CompoundsLewis Dot SymbolsIonic Compounds and Ionic BondingChemical FormulasLattice EnergyIonic Compound NomenclatureLewis Theory of BondingCovalent BondingLaws of Definite Proportions and Multiple ProportionsMolecular, Structural, and Empirical FormulasMolecular Compound NomenclatureInorga

55、nic and Organic CompoundsPolyatomic IonsOxyanionsOxoacidsHydratesChemistry: Atoms FirstJulia Burdge & Jason OverbyChapter 6Representing MoleculesChemical Bonding I: Basic Concepts66.1The Octet RuleLewis StructuresMultiple Bonds6.2Electronegativity and PolarityElectronegativityDipole Moment, Partial

56、Charges and Percent Ionic Character6.3Drawing Lewis Structures6.4Lewis Structures and Formal Charge6.5Resonance6.6Exceptions to the Octet RuleIncomplete OctetsOdd Numbers of ElectronsExpanded OctetsAccording to the octet rule, atoms will lose, gain, or share electrons in order to achieve a noble gas

57、 electron configuration.Only valence electrons contribute to bonding.FF+F FEach F counts both shared electrons to “feel” as though it has a Ne configuration.F 1s22s22p5valence electronsThe Octet Rule6.1The Octet RuleOnly two valence electrons participate in the formation of the F2 bond.Pairs of vale

58、nce electrons not involved in bonding are called lone pairs.F FF FF ForLewis StructuresA Lewis structure is a representation of covalent bonding.Shared electron pairs are shown either as dashes or as pairs of dots.Lone pairs are shown as pairs of dots on individual atoms.HOHHOHO with 8 eH with 2 eH

59、with 2 eShared electrons shown as dashes (bonds)Multiple BondsIn a single bond, atoms are held together by one electron pair.In a double bond, atoms share two pairs of electrons.HOHC with 8 eO with 8 eO with 8 eone shared pair of electrons results in a single bondOCO2 shared pairs of electrons resul

60、t in double bondsOCO=HOHMultiple BondsA triple bond occurs when atoms are held together by three electron pairs.each N has 8 e3 shared pairs of electrons result in a triple bondNNNNMultiple BondsBond length is defined as the distance between the nuclei of two covalently bonded atoms.Multiple BondsMu