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Chapter 12
Chemical Bonding
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2. Figure 12.1: The formation of a bond between two atoms.
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Figure 12.2: Probability representations of the electron sharing in HF.
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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.
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Table 12.1
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6. Figure 12.3: Electronegativity values for selected elements.
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7. Figure 12.4: The three possible types of bonds.
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8. Figure 12.5: Charge distribution in the water molecule.
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Questions
An example of a ionic bond – NaCl
An example of a polar covalent bond – HF
An example of a covalent bond – O2
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Figure 12.5: Water molecule behaves as if it had a positive and negative end.
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Figure 12.6: Polar water molecules are strongly attracted to positive ions by their negative ends.
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Figure 12.6: Polar water molecules are strongly attracted to negative ions by their positive ends.
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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.
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Table 12.2
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Table 12.3
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16. Figure 12.8: Ions as packed spheres.
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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.
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18. Figure 12.8: Positions (centers) of the ions.
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19. Figure 12.9: Relative sizes of some ions and their parent atoms.
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20. Figure 12.12: Molecular structure of methane.
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21. 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.
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22. Section 12.2 Review Questions page 412 # 1-7
Mg: [Ne] 3s S: [Ne] 3s2 3p Compound: MgS
K: [Ar] 4s Cl: [Ne] 3s2 3p Compound KCl
Cs: [Xe] 6s F:[He] 2s2 2p Compound CsF
Ba: [Xe] 6s 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
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23. Figure 12.13: Tetrahedral arrangement of electron pairs.
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Figure 12.13: Hydrogen atoms occupy only three corners of the tetrahedron.
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25. Figure 12.13: The NH3 molecule has the trigonal pyramid structure.
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Figure 12.14: Tetrahedral arrangement of four electron pairs around oxygen.
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Figure 12.14: Two electron pairs shared between oxygen and hydrogen atoms.
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28. Figure 12.14: V-shaped molecular structure of the water molecule.
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Table 12.4
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