Part A. 1. For the molecules CH4, NH3, and H2O, what conclusions can you make co
ID: 792532 • Letter: P
Question
Part A.
1. For the molecules CH4, NH3, and H2O, what conclusions can you make concerning the H-X-H bond angle and the number of unshared (lone) pairs of electrons around the central atom X?
2. What conclusions can you make concerning the size of the central atom X and the X-H bond length?
Part B
3. Consider O3 and NO3-. Look at the O-O and N-O bond lengths within each molecule. Are they the same or different? Use resonance structures to explain your observations.
Part C.
1. Compare the four models of CHBrICI. Are they all the same (superimposable on each other? If the answer is yes, can you construct any that are not the same?
2. If you were able to construct models that were superimposable, draw them in your lab notebook. What is the relationship between the two models, if any? In other words, how do they resemble one another?
3. If you generated non-superimposable models, do you expect your molecules to have different physical properties? Why or why not?
Explanation / Answer
Methane is a tetrahedral molecule with four equivalent C-H bonds. Its electronic structure is described by four bonding molecular orbitals (MOs) resulting from the overlap of the valence orbitals on C and H. The lowest energy MO is the result of the overlap of the 2s orbital on carbon with the in-phase combination of the 1s orbitals on the four hydrogen atoms. Above this level in energy is a triply degenerate set of MOs that involve overlap of the 2p orbitals on carbon with various linear combinations of the 1s orbitals on hydrogen. The resulting "three-over-one" bonding scheme is consistent with photoelectron spectroscopic measurements.
At room temperature and standard pressure, methane is a colorless, odorless gas.[5] The familiar smell of natural gas as used in homes is a safety measure achieved by the addition of an odorant, usually blends containing tert-butylthiol. Methane has a boiling point of ?161