Feb 17

Alkali of the week

Strontium (Sr)


Strontium is an Alkali earth metal with an atomic number of 38. It is naturally found in the minerals celestine and strontianite. It is a highly reactive metal in both water and air, which makes it useful in pyrotechnics. One of Strontium's isotopes, strontium 90, is one of the constituents of radioactive fallout, but like other radioactive materials, which have very long half lives, strontium's half life is only 28.90 years. Besides pyrotechnics, strontium is also used in alloys, in the glass of color televisions to prevent radiation exposure, in toothpaste, in the study of neurotransmitter release, and as a pharmaceutical medicine for osteoporosis.


What is a mole?


I thought this article from Buck and Herbert could have been written more clearly, but perhaps it is I who lacks clarity. The mole and Avogadro's number is a sort of mental tongue twister. For instance the sentence, "The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilograms of carbon 12," is clear enough, but the word "system" and phrase "elementary entities" definitely made me reread it (a mole number of times). I prefer this approach: "What is that number of molecules that weighs in grams what the molecule weighs in relative atomic weight units?"  What is also puzzling is that the equal volume of differing gases will have the same number of molecules. Why is that? Don't the molecules take up different amounts of space? I guess I will read the article one mole time. 


Avogadro's hypothesis


I thought this was a good introduction into hypothesis and theory using the great Avogadro as and his counterparts as examples. The article shows the journey that ideas take from hypothesis to theories and how they are tested. Despite the "objectivity" of science, politics and ego still does have its say (at least for a while), and we can see this in the crushing and rising of people and their ideas throughout scientific history. As for my understanding of Avogadro's hypothesis I did indeed pass the test.