Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings Covalent Bonds 4.6 Naming and Writing Formulas of Covalent Compounds 4.7 Bond Polarity Chapter 4 Compounds and Their Bonds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 2  Covalent bonds form between two nonmetals from Groups 4A, 5A, 6A, and 7A.  In a covalent bond, electrons are shared to complete octets. Covalent Bonds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 3 Indicate whether a bond between the following is 1) Ionic2) Covalent ____A.sodium and oxygen ____B.nitrogen and oxygen ____C. phosphorus and chlorine ____D.calcium and sulfur ____E.chlorine and bromine Learning Check

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 4 Indicate whether a bond between the following is 1) Ionic2) Covalent 1 A. sodium and oxygen 2 B. nitrogen and oxygen 2 C. phosphorus and chlorine 1 D. calcium and sulfur 2 E. chlorine and bromine Solution

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 5 In hydrogen, two hydrogen atoms share their electrons to form a covalent bond. Each hydrogen atom acquires a stable outer shell of two (2) electrons like helium (He). H  +  H H : H = H  H = H 2 hydrogen molecule H 2, A Covalent Molecule

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 6 Diatomic Elements As elements, the following share electrons to form diatomic, covalent molecules.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 7 What is the name of each of the following diatomic molecules? H 2 hydrogen N 2 nitrogen Cl 2 _______________ O 2 _______________ I 2 _______________ Learning Check

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 8 What are the names of each of the following diatomic molecules? H 2 hydrogen N 2 nitrogen Cl 2 chlorine O 2 oxygen I 2 iodine Solution

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 9 The compound NH 3 consists of a N atom and three H atoms.    N  and 3 H   By sharing electrons to form NH 3, the electron dot structure is written as H Bonding pairs   H : N : H   Lone pair of electrons Covalent Bonds in NH 3

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 10 Number of Covalent Bonds Often, the number of covalent bonds formed by a nonmetal is equal to the number of electrons needed to complete the octet.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 11 Dot Structures and Models of Some Covalent Compounds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 12 Multiple Bonds  Sharing one pair of electrons is a single bond. X : X or X–X  In multiple bonds, two pairs of electrons are shared to form a double bond or three pairs of electrons are shared in a triple bond. X : : X or X =X X : : : X or X ≡ X

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 13 In nitrogen, octets are achieved by sharing three pairs of electrons. When three pairs of electrons are shared, the multiple bond is called a triple bond. octets          N  +  N   N:::N  triple bond Multiple Bonds in N 2

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 14 In the name of a covalent compound, the first nonmetal is named followed by the name of the second nonmetal ending in –ide.  Prefixes indicate the number of atoms of each element. Naming Covalent Compounds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 15 Complete the name of each covalent compound: COcarbon ______oxide CO 2 carbon _______________ PCl 3 phosphorus ___________ CCl 4 carbon _______________ N 2 O______________________ Learning Check

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 16 Complete the name of each covalent compound: CO carbon monoxide CO 2 carbon dioxide PCl 3 phosphorus trichloride CCl 4 carbon tetrachloride N 2 Odinitrogen monoxide Solution

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 17 Formulas and Names of Some Covalent Compounds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 18 Select the correct name for each compound. A.SiCl 4 1) silicon chloride 2) tetrasilicon chloride 3) silicon tetrachloride B. P 2 O 5 1) phosphorus oxide 2) phosphorus pentoxide 3) diphosphorus pentoxide C.Cl 2 O 7 1) dichlorine heptoxide 2) dichlorine oxide 3) chlorine heptoxide Learning Check

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 19 Select the correct name for each compound. A.SiCl 4 3) silicon tetrachloride B. P 2 O 5 3) diphosphorus pentoxide C.Cl 2 O 7 1) dichlorine heptoxide Solution

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 20  Electronegativity is the attraction of an atom for shared electrons.  The nonmetals have high electronegativity values with fluorine as the highest.  The metals have low electronegativity values. Electronegativity

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 21 Some Electronegativity Values for Group A Elements

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 22  The atoms in a nonpolar covalent bond have electronegativity differences of 0.3 or less.  Examples: Atoms Electronegativity Type of Difference Bond N-N = 0.0 Nonpolar covalent Cl-Br = 0.2 Nonpolar covalent H-Si = 0.3 Nonpolar covalent Nonpolar Covalent Bonds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 23  The atoms in a polar covalent bond have electronegativity differences of 0.4 to 1.6.  Examples: Atoms Electronegativity Type of Difference Bond O-Cl = 0.5 Polar covalent Cl-C = 0.5 Polar covalent O-S = 1.0 Polar covalent Polar Covalent Bonds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 24 Comparing Nonpolar and Polar Covalent Bonds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 25 Ionic Bonds  The atoms in an ionic bond have electronegativity differences of 1.7 or more.  Examples: Atoms ElectronegativityType of Difference Bond Cl-K 3.0 – 0.8 = 2.2Ionic N-Na 3.0 – 0.9 = 2.1Ionic S-Cs2.5 – 0.7= 1.8Ionic

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 26 Range of Bond Types

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 27 Predicting Bond Type

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 28 Identify the type of bond between the following as 1) nonpolar covalent 2) polar covalent 3) ionic A. K-N B. N-O C. Cl-Cl Learning Check

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 29 A. K-N 3) ionic B. N-O 2) polar covalent C. Cl-Cl 1) nonpolar covalent Solution

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings Polyatomic Ions Chapter 4 Compounds and Their Bonds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 31 A polyatomic ion is a group of two or more atoms that has an overall ionic charge. Some examples of polyatomic ions are NH 4 + ammoniumOH - hydroxide NO 3 - nitrateNO 2 - nitrite CO carbonatePO phosphate HCO 3 - hydrogen carbonate (bicarbonate) Polyatomic Ions

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 32 Common Polyatomic Ions

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 33 Formulas with Polyatomic Ions The formula of an ionic compound containing a polyatomic ion is written to make the overall charge equal zero (0). Na + and NO 3 - NaNO 3 When two or more polyatomic ions are needed, the polyatomic ion is enclosed in parentheses. polyatomic ion Mg 2+ and NO 3 - Mg(NO 3 ) 2 subscript 2 for charge balance

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 34 Some Compounds with Polyatomic Ions

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 35 Select the correct formula for each: A. Aluminum nitrate 1) AlNO 3 2) Al(NO) 3 3) Al(NO 3 ) 3 B. Copper(II) nitrate 1) CuNO 3 2) Cu(NO 3 ) 2 3) Cu 2 (NO 3 ) C. Iron (III) hydroxide 1) FeOH2) Fe 3 OH3) Fe(OH) 3 D. Tin(IV) hydroxide 1) Sn(OH) 4 2) Sn(OH) 2 3) Sn 4 (OH) Learning Check

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 36 Select the correct formula for each: A. Aluminum nitrate 3) Al(NO 3 ) 3 B. Copper(II) nitrate 2) Cu(NO 3 ) 2 C. Iron (III) hydroxide 3) Fe(OH) 3 D. Tin(IV) hydroxide 1) Sn(OH) 4 Solution

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 37  For compounds with polyatomic ions, the positive ion is named first followed by the name of the polyatomic ion. NaNO 3 sodium nitrate K 2 SO 4 potassium sulfate Al(HCO 3 ) 3 aluminum bicarbonate or aluminum hydrogen carbonate (NH 4 ) 3 PO 4 ammonium phosphate Naming Compounds with Polyatomic Ions

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 38 Match each formula with the correct name: A. Na 2 CO 3 1) magnesium sulfite MgSO 3 2) magnesium sulfate MgSO 4 3) sodium carbonate B. Ca(HCO 3 ) 2 1) calcium carbonate CaCO 3 2) calcium phosphate Ca 3 (PO 4 ) 2 3) calcium bicarbonate Learning Check

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 39 A. Na 2 CO 3 3) sodium carbonate MgSO 3 1) magnesium sulfite MgSO 4 2) magnesium sulfate B. Ca(HCO 3 ) 2 3) calcium bicarbonate CaCO 3 1) calcium carbonate Ca 3 (PO 4 ) 2 2) calcium phosphate Solution

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 40 Summary of Naming Compounds

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 41 Naming Rules

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 42 Naming Rules (continued)

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 43 Learning Check Name each of the following compounds: A.Mg(NO 3 ) 2 B.CuCl 2 C.N 2 O 4 D.Fe 2 (SO 4 ) 3 E.Ba 3 (PO 4 ) 2

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 44 Solution Name each of the following compounds: A.Mg(NO 3 ) 2 magnesium nitrate B.CuCl 2 copper(II) chloride C.N 2 O 4 dinitrogen tetroxide D.Fe 2 (SO 4 ) 3 iron(III) sulfate E.Ba 3 (PO 4 ) 2 barium phosphate

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 45 Learning Check Write the correct formula for each: A.potassium sulfide B.calcium carbonate C.sodium phosphite D.iron(III) oxide E.iron (II) nitrate

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 46 Solution Write the correct formula for each: A.potassium sulfideK 2 S B.calcium carbonateCaCO 3 C.sodium phosphiteNa 3 PO 3 D.iron(III) oxideFe 2 O 3 E.iron (II) nitrateFe(NO 3 ) 2

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 47 Chapter 4 Compounds and Their Bonds 4.9 Shapes of Molecules 4.10Polar and Nonpolar Molecules

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 48 VSEPR The shape of a molecule is predicted from the geometry of the electrons pairs around the central atom. In the valence-shell electron-pair repulsion theory (VSEPR), the electron pairs are arranged as far apart as possible to give the least amount of repulsion of the negatively charged electrons.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 49 Two Electron Pairs In a molecule of BeCl 2, there are two bonding pairs around the central atom Be. (Be is an exception to the octet rule.) The arrangement of two electron pairs to minimize their repulsion is 180° or opposite each other. The shape of the molecule is linear.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 50 Two Electron Pairs with Double Bonds The electron-dot structure for CO 2 consists of two double bonds to the central atom C. Because the electrons in a double bond are held together, a double bond is counted as a single unit. Repulsion is minimized when the double bonds are placed opposite each other at 180° to give a linear shape.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 51 Three Electron Pairs In BF 3, there are 3 electron pairs around the central atom B. (B is an exception to the octet rule.) Repulsion is minimized by placing three electron pairs in a plane at angles of 120°, which is a trigonal planar arrangement. The shape with three bonded atoms is trigonal planar.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 52 Two Bonding Pairs and A Nonbonding Pair In SO 2, there are 3 electron units around the central atom S. Two electron units are bonded to atoms and one electron pair is a nonbonding pair. Repulsion is minimized by placing three electron pairs in a plane at angles of 120°, which is trigonal planar. The shape with two bonded atoms is bent.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 53 Learning Check The shape of a molecule of N 2 O (N N O) is 1) linear 2) trigonal planar 3) bent (120°)

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 54 Solution The shape of a molecule of N 2 O (N N O) is 1) linear The electron-dot structure uses 5 e for each N and 6 e for O (16 e total) has octets using two double bond to the central N and one nonbonding pair. The shape with two bonded atoms is linear. : N :: N :: O :

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 55 Four Electron Pairs In CH 4, there are 4 electron pairs around the central atom C. Repulsion is minimized by placing four electron pairs at angles of 109°, which is a tetrahedral arrangement. The shape with four bonded atoms is called tetrahedral.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 56 Three Bonding Atoms and One Nonbonding Pair In NH 3, there are 4 electron pairs around the N. Three pairs are bonded to atoms and one is a nonbonding pair. Repulsion is minimized by placing four electron pairs at angles of 109°, which is a tetrahedral arrangement. The shape with three bonded atoms is pyramidal.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 57 Two Bonding Atoms and Two Lone Pairs In H 2 O, there are 4 electron pairs around O. Two pairs are bonded to atoms and two are nonbonding pairs. Repulsion is minimized by placing four electron pairs at angles of 109° called a tetrahedral arrangement. The shape with two bonded atoms is called bent.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 58 Some Steps Using VSEPR to Predict Shape Draw the electron dot structure. Count the electron pairs around the central atom. Arrange the electron pairs to minimize repulsion. Determine the shape using the number of bonded atoms in the electron arrangement.

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 59 Summary of Electron Arrangements and Shapes

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 60 Learning Check Use VSEPR theory to determine the shape of the following molecules or ions. 1) tetrahedral 2) pyramidal3) bent A. PF 3 B. H 2 S C. CCl 4 D. PO 4 3-

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 61 Solution Use VSEPR theory to determine the shape of the following molecules or ions. 1) tetrahedral2) pyramidal 3) bent A. PF 3 2) pyramidal B.H 2 S3) bent C. CCl 4 1) tetrahedral D. PO ) tetrahedral

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 62 Polar Molecules A polar molecule contains polar bonds. The separation of positive and negative charge is called a dipole. In a polar molecule, dipoles do not cancel.  +  - H–Cl Cl–N–Cl dipole Cl dipoles do not cancel

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 63 Nonpolar Molecules A nonpolar molecule contains nonpolar bonds Cl–ClH–H or a symmetrical arrangement of polar bonds. O=C=O Cl Cl–C–Cl Cl dipoles cancel

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 64 Learning Check Identify each of the following molecules as 1) polar or 2) nonpolar. Explain. A. PBr 3 B. HBr C. Br 2 D. SiBr 4

Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 65 Solution Identify each of the following molecules as 1) polar or 2) nonpolar. Explain. A. PBr 3 1) polar; pyramidal B. HBr1) polar; polar bond C. Br 2 2) nonpolar, nonpolar bond D. SiBr 4 2) nonpolar; dipoles cancel