Harder Questions

What advantages does computational chemistry have over wet chemistry  

Was there computational chemistry before electronic computers were available  

Can conventional physical chemistry, such as the study of kinetics, thermodynamics, spectroscopy and electrochemistry, be regarded as a kind of computational chemistry  

The properties of a molecule that are most frequently calculated are geometry, energy (compared to that of other isomers), and spectra. Why is it more of a challenge to calculate simple properties like melting point and density Hint is there a difference between a molecule X and the substance X  

Is it surprising that the geometry and energy (compared to that of other isomers) of a molecule can often be accurately calculated by a ball-and-springs model (molecular mechanics)  

Hint Is there a difference between a molecule X and the substance X  

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In Chapter 2 you were introduced to atoms and in Chapter 6 they were described in more detail. You were told that the atom contains charged particles, that it has a nucleus made up of neutrons and protons, and that the nucleus is surrounded by electrons. The atom is incredibly small but the nucleus is even smaller. But also you were told that every theory (including the atomic theory) should be thought about and criticized—the evidence upon which it is based should be examined and understood. It is one thing to ask Do we believe in atoms and quite another to ask Why do we believe in atoms In this chapter we shall try to answer this last, harder question. 

Schmidt That s a harder question. The data are clear the mouse can make a duct, but it cannot put a lobuloalveolar structure on the outside of this. There is even a third question is Dl specifying some kind of a cell fate ... 

I Answer the questions that are easiest for you first. You do not have to go in order from start to finish. Read each question and, if you are not sure what to do, move on to the next question. You can go back to harder questions if you have time at the end. 

Some molecular species are not calculated properly by straightforward model chemistries these include singlet diradicals and some excited state species. For these the standard method is the complete active space approach, CAS (CASSCF, complete active space SCF). This is a limited version of configuration interaction, in which electrons are promoted from and to a limited, carefully chosen set of molecular orbitals. CASSCF calculations require care in choosing these orbitals and in judging the reliability of the results (see e.g. Singlet Diradicals, Harder Questions, Questions 3 and 4). 

This was put in the Harder Questions category because the answer can t be found just be reading the chapter, but actually the solution comes from a straightforward application of simple physics. 

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