🧪AP Chemistry
3. Answer the following questions about the element germanium (Ge).
The mass spectrum for a sample of pure germanium is shown in Figure 1. The spectrum identifies the five naturally occurring isotopes of germanium.
Figure 1. Mass spectrum of germanium (Ge): relative abundance (%) versus mass number for the five naturally occurring isotopes.
Identify the number of neutrons in the isotope corresponding to the tallest peak in Figure 1.
Explain why the atomic mass of germanium listed on the periodic table (72.63 amu) is not equal to the mass of any individual isotope shown in Figure 1.
The photoelectron spectrum (PES) for germanium is shown in Figure 2.
Figure 2. Photoelectron spectrum (PES) of germanium (Ge): relative number of electrons versus binding energy (MJ/mol) on a logarithmic x-axis that decreases from left to right.
Based on the peaks in Figure 2, write the complete ground-state electron configuration for the Ge atom.
The peak at 1.5 MJ/mol in Figure 2 corresponds to the 4s subshell. Explain why the peak for the 4p subshell is located at a lower binding energy (0.7 MJ/mol) than the 4s peak, using principles of atomic structure.
Answer the following questions comparing germanium to silicon (Si), which is in the same group on the periodic table.
The atomic radius of Ge is 122 pm, while the atomic radius of Si is 111 pm. Explain this difference in terms of atomic structure.
The first ionization energy of Ge is 762 kJ/mol, while the first ionization energy of Si is 786 kJ/mol. Explain why the first ionization energy of Ge is lower than that of Si.
A student performs an experiment to determine the empirical formula of a germanium chloride compound. The student heats a sample of pure germanium in the presence of excess chlorine gas. The data from the experiment are recorded in Table 1.
Table 1. Experimental data for germanium chloride synthesis
Measurement | Mass (g) |
|---|---|
Mass of empty crucible | 25.000 |
Mass of crucible + Ge sample | 26.452 |
Mass of crucible + germanium chloride product | 29.288 |
Calculate the number of moles of Ge and the number of moles of Cl that reacted, using the data in Table 1.
Determine the empirical formula of the germanium chloride formed.
In a second trial, the student uses a sample of germanium that is contaminated with an inert impurity. The student assumes the sample is pure germanium. Would the calculated ratio of moles of Cl to moles of Ge be greater than, less than, or equal to the actual ratio in the compound? Justify your answer.
Germanium can also form the Ge²⁺ ion. Write the complete electron configuration for the Ge²⁺ ion.
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