Chemical Puzzle Number

Unless one is familiar with the basics of carbocation chemistry, these puzzles will be as baffling nowadays as they were to the chemists who were confronted with them and many similar ones in the late nineteenth and early twentieth century. It is now time to look in more detail at carbocation chemistry. 

---

Beyond their practical value, extremophile enzymes present scientists with a fundamental puzzle. Fike all molecular characteristics, their exceptional stability must originate in their chemical structures. However, it is not yet certain what structural features determine these properties. What is known is that in their active folded form, cold-resistant enzymes appear to have relatively fewer structure-stabilizing interactions between different parts of the amino acid chain. As a result, they remain more flexible at a lower temperature than ordinary enzymes but unfold and lose their activity more quickly as the temperature is raised. Conversely, heat-resistant enzymes seem to have a larger number of... 

Bohr s theory not only solved the puzzle of the rare earths, it also explained why Mendeleev s periodic law works so well in most cases. Elements with the same number of electrons in the outermost shell have similar properties. For example, both sodium and potassium have a single electron in the outer shell. Magnesium and calcium, which are also chemically and physically similar, each have two. Carbon and silicon have four. And so on. 

This book concerns the common atoms of our natural world. How many of each element exist, and why What variations are found in the relative numbers of the isotopes of each element, and how are those variations interpreted If I could write an epic poem, I would lyricize over the history of the universe writ small by their natural abundances. I would rhapsodize over the puzzling arrangements at different times and places of the thousand or so different isotopes of some ninety chemical elements. These different arrangements speak of distant past events. 

The next stage in the research project will focus upon those location points where significant variation exists, or where the data collected are puzzling. Selection of a limited number of points for the physical and chemical testing would preserve at least part of the evidence and assist in the search for information about the character of the fiber. An array of instrumental analyses would be designed to yield essential data about the textile evidence and its mineralization processes. 

In contrast to the small number of differentiated parent bodies represented by evolved achondritic meteorites, the number of parent bodies inferred from the chemical compositions of iron meteorites may be as large as 50 (Wasson, 1990). Of the 13 major iron meteorite groups, 10 appear to be from cores of differentiated meteorites. Many additional cores are inferred from the ungrouped irons, which make up —15% of iron meteorites. It is a puzzle why we appear to sample many more cores than mantles of these asteroids (see Chapter 1.12 for further discussion). 

---