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Unformatted text preview: 159 Chapter 37 Molecules Conceptual Problems 1 • [SSM] Would you expect NaCl to be polar or nonpolar? Determine the Concept Yes. Because the center of charge of the positive Na ion does not coincide with the center of charge for the negative Cl ion, the NaCl molecule has a permanent dipole moment. Hence, it is a polar molecule. 2 • Would you expect N 2 to be polar or nonpolar? Determine the Concept Because a N 2 molecule has no permanent dipole moment, it is a non-polar molecule. 3 • Does neon naturally occur as Ne or Ne 2 ? Explain your answer. Determine the Concept No. Neon naturally occurs as Ne, not Ne 2 . Neon is a rare gas atom with a closed shell electron configuration. 4 • What type of bonding mechanism would you expect for atoms of ( a ) HF, ( b ) KBr, ( c ) N 2 , ( d ) Ag in solid silver? Determine the Concept ( a ) Because an electron is transferred from the H atom to the F atom, the bonding mechanism is ionic. ( b ) Because an electron is transferred from the K atom to the Br atom, the bonding mechanism is ionic. ( c ) Because the atoms share two electrons, the bonding mechanism is covalent. ( d ) Because each valence electron is shared by many atoms, the bonding mechanism is metallic bonding. 5 •• [SSM] The elements on the far right column of the periodic table are sometimes called noble gases, both because they are gasses under a wide range of conditions, and because atoms of these elements almost never react with other atoms to form molecules or ionic compounds. However, atoms of noble gases can react if the resulting molecule is formed in an electronic excited state. An example is ArF. When it is formed in the excited state, it is written ArF* and is called an excimer (for ex cited dimer ). Refer to Figure 37-13 and discuss how a Chapter 37 160 diagram for the electronic, vibrational, and rotation energy levels of ArF and ArF* would look in which the ArF ground state is unstable and the ArF* excited state is stable. Remark: Excimers are used in certain kinds of lasers . Determine the Concept The diagram would consist of a non-bonding ground state with no vibrational or rotational states for ArF (similar to the upper curve in Figure 37-4) but for ArF* there should be a bonding excited state with a definite minimum with respect to inter-nuclear separation and several vibrational states as in the excited state curve of Figure 37-13. 6 • Find other atoms that have the same subshell electron configurations in their two highest energy orbitals as carbon atoms do. Would you expect the same type of hybridization for these orbitals as for carbon? Determine the Concept Elements similar to carbon in outer shell configurations are silicon, germanium, tin, and lead. We would expect the same hybridization for these as for carbon, and this is indeed the case for silicon and germanium whose crystal structure is the diamond structure. Tin and lead, however, are metallic and here the metallic bond is dominant....
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