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6 Electronic Structure of Atoms Solutions to Exercises 6.95 (a) Si: 2 unpaired electrons (b) Zn: [Ar]4s²3d¹⁰, 0 unpaired electrons (c) Zr: [Kr]5s²4d², 2 unpaired electrons (d) Sn: 2 unpaired electrons (e) Ba: [Xe]6s², 0 unpaired electrons (f) TI: 1 unpaired electrons 6.96 The core would be the electron configuration of element 118. If no new subshell begins to fill, the condensed electron configuration of element 126 would be similar to those of elements vertically above it on the periodic chart, Pu and Sm. The condensed configuration would be On the other hand, the 5g subshell could begin to fill after 8s, resulting in the condensed configuration Exceptions are also possible (likely). Integrative Exercises 6.97 (a) We know the wavelength of microwave radiation, the volume of coffee to be heated, and the desired temperature change. Assume the density and heat capacity of coffee are the same as pure water. We need to calculate: (i) the total energy required to heat the coffee and (ii) the energy of a single photon in order to find (iii) the number of photons required. (i) From Chapter 5, the heat capacity of liquid water is To find the mass of 200 mL of coffee at 23°C, use the density of water given in Appendix B. 200 mL 0.997 1 mL = = g coffee 199.4 g = 3.087 X 10⁴ J = kJ 1g°C (ii) 1.77 10⁻²⁴ J = 1 photon (iii) 3.087 10⁴ J 1.774 1 photon X 10⁻²⁴ J = 1.7 X 10²⁸ photons (The answer has 2 sig figs because the temperature change, 37°C, has 2 sig figs.) (b) 1 W=1J/s. 900 W = From part (a), 31 kJ are required to heat the coffee. 3.087 10⁴ J 1s = 162