Copyright© by Houghton Mifflin Company. All rights reserved. Chapter 12 UNIT 7 Chemical Bonding Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.1: The formation of a bond between two atoms. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Figure 12.2: Probability representations of the electron sharing in HF. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Electronegativity Electronegativity – The tendency of an atom in a molecule to attract shared electrons to itself. The range of electronegativity values goes from 4.0 for fluorine to 0.7 for cesium. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Table 12.1 Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.3: Electronegativity values for selected elements. Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.4: The three possible types of bonds. Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.5: Charge distribution in the water molecule. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Questions An example of a ionic bond – NaCl An example of a polar covalent bond – HF An example of a covalent bond – O2 Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Figure 12.5: Water molecule behaves as if it had a positive and negative end. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Figure 12.6: Polar water molecules are strongly attracted to positive ions by their negative ends. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Figure 12.6: Polar water molecules are strongly attracted to negative ions by their positive ends. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Question What rule helps us determine the most stable electron configuration and charge of a particular ion? Atoms achieve noble gas electron configurations in almost all stable chemical compounds. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Table 12.2 Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Table 12.3 Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.8: Ions as packed spheres. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Question In general, how do electronegativity trends compare to trends of atomic size? In general, the smaller the atomic size, the greater the electronegativity of the atoms. Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.8: Positions (centers) of the ions. Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.9: Relative sizes of some ions and their parent atoms. Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.12: Molecular structure of methane. Copyright© by Houghton Mifflin Company. All rights reserved.

Section 12.2 Review Questions page 412 # 1-7 A Group 1 or 2 metal loses the number of electrons required for it to reach the electron configuration of the previous noble gas. For example Na lose one electron and Ca loses two. Once oxygen has gained two electrons, it has the same electron configuration as neon. First write out the electron configuration of the atom. Then determine how many electrons to add or remove from the atom to give a noble gas electron configuration. Once you know the charges of the cation ans anion, you can predict the formula, keeping in mind that chemical compounds are always electrically neutral. Copyright© by Houghton Mifflin Company. All rights reserved.

Section 12.2 Review Questions page 412 # 1-7 Mg: [Ne] 3s2 S: [Ne] 3s2 3p4 Compound: MgS K: [Ar] 4s1 Cl: [Ne] 3s2 3p5 Compound KCl Cs: [Xe] 6s1 F:[He] 2s2 2p5 Compound CsF Ba: [Xe] 6s2 Br: [Ar] 4s2 3d10 4p5 Compound BaBr2 5. Cations are smaller than their parent atoms because the electrons in the valence level are removed and the remaining electrons are pulled closer to the cation’s nucleus by the positive charge imbalance. Anions are larger than their parent atoms because electrons are added , increasing the electron-electron repulsions causing the electron cloud to become larger. 6. Polyatomic ions contain covalently bonded atoms within the group that carries the charge. Example OH- 7. K+ , Ca2+ , S2- , Cl- Electron configuration 1s22s22p63s23p6 Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.13: Tetrahedral arrangement of electron pairs. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Figure 12.13: Hydrogen atoms occupy only three corners of the tetrahedron. Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.13: The NH3 molecule has the trigonal pyramid structure. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Figure 12.14: Tetrahedral arrangement of four electron pairs around oxygen. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Figure 12.14: Two electron pairs shared between oxygen and hydrogen atoms. Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 12.14: V-shaped molecular structure of the water molecule. Copyright© by Houghton Mifflin Company. All rights reserved.

Copyright© by Houghton Mifflin Company. All rights reserved. Table 12.4 Copyright© by Houghton Mifflin Company. All rights reserved.