Posted: March 26th, 2021
Answer each question in NO more than 200 words.
1. The trend for the number of bonds formed by an atom is C > N > O > F. Explain the trend.
2. Explain the difference between the terms ion charge and formal charge.
3. Solid sodium chloride does not conduct electricity, but molten (liquid) sodium chloride at greater than 800 0C does conduct electricity. Why is this true?
4. Explain why ethanol (CH3CH2OH) does NOT form an aqueous solution that conducts electricity.
5. Predict which of the following species will form an aqueous solution that will conduct electricity: C6H6 (benzene), C6H12O6 (glucose), NaCl, Si. Explain the mechanism of the observed conductivity.
6. An atom has 3 electron shells and 2 electrons in the outermost shell. What element is this?
7. Consider this statement: If the bond order between two atoms is 1.5, then there must be two resonance structures.Is this statement true or false? Give an example to provide evidence to support your choice.
8. What type of bonding is encountered in metal hydrides, such as NaH, MgH2, etc. Explain your answer.
9.Consider the following five molecules, which are all liquids at room temperature.
10. Is it possible for a molecule containing polar bonds to be non-polar? Explain your answer. Provide an example to support your explanation.
11. Which of the above molecules are polar?
12. Explain why carbon dioxide (CO2) is non-polar, and diethyl ether (CH3OCH3) is polar.
13. Use Coulomb’s law to explain why sodium (Na) is more electronegative than cesium (Cs), even though the nuclear charge on Cs is larger than that of Na. To answer this question you need to consider both the effective nuclear charge felt by the valence electrons and the distance of those electrons from the nucleus. The effective nuclear charge is approximated as the total nuclear charge minus the number of core electrons. Thus, effectively, core electrons decrease the nuclear charge felt by the valence electrons because they are between the nucleus and the valence electrons.
14. In X-ray photoelectron spectrometry one measures kinetic energy of ejected electrons. How does this measurement allow one to determine the ionization energies of the atoms being analyzed?
15. To ionize a 1s electron in a Ne atom, an X-ray photon with energy of 84000 kJ/mol is required. If the same X-ray source is used to generate a photoelectron spectrum of sodium atoms, how many different lines do you expect to record? Assign each of these lines (in energy order) to the ionization of a specific atomic orbital of Na.
16. The ionization energies increase monotonically for B, C, N and also (separately) for O, F, Ne. However IE(O) < IE(N). Explain these two facts.
17. Explain in your own words what the difference is between an electron wave function and an electron probability density.
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