Showing posts with label Dalton. Show all posts
Showing posts with label Dalton. Show all posts

September 3, 2012 = Dalton Introduces Atomic Symbols


– 1803 
Most things in nature are a big mash-up of all sorts of materials, and it took chemists and physicists years to figure out what it is, exactly, that makes up our world (and the universe).

English chemist and physicist John Dalton was a big part of figuring it all out. On this date in 1803 he wrote some notes on “ultimate particles” (also known as “atoms,” which aren't all that ultimate, after all, since we now know that atoms are made up of smaller particles). Dalton proposed the idea that there are fundamental kinds of stuff, called elements, and that each element is made up of atoms of different masses. Atoms of gold, for example, would be much heavier than atoms of hydrogen. As Dalton wrote about a variety of elements, he used symbols to represent each element.

And that's the first time that anyone used a symbol to represent an element!

We don't use Dalton's symbols anymore, but many of his symbols were initial letters surrounded by circles, such as S for silver, C for copper, and Z for zinc. We do use this general idea: nowadays, one or two letters (without the circle) is the symbol for each element.

Our modern symbology was created by Swiss scientist Jons Kakob Berzelius, and naturally he did not use English as the basis for his symbols, as Dalton did. Instead, he used the shared language of science of his time, Latin, as the basis for his symbols. Because of this Latin origin, some of our modern elemental symbols don't match up with the English names:

Iron = Fe           (ferrum)
Silver = Ag        (argentum)
Gold = Au         (aurum)
Lead = Pb         (plumbum)
Potassium = K  (kalium)
Copper = Cu     (cuprum)
Antimony = Sb  (stibium)
Mercury = Hg    (hydrargyrum)
Tungsten = W   (wolfram)
Tin = Sn            (stannum)
Sodium = Na     (natrium)

By the way...
Today the shared language of science is English.

Also on this date:





October 23, 2011 - National Mole Day


Avogadro's number, commonly used in chemistry, is 6.02 × 1023, and that is why we celebrate Avogadro's number from 6:02 in the morning until 6:02 in the evening on 10/23.

And, yes, we who celebrate such a chemical constant are geeks! Thanks for asking!







But...why is a day celebrating Avogadro's number called Mole Day?

Well, Avogadro's number has to with “moles,” which is an amount. For any sort of molecule, one mole is a mass in grams whose number is equal to the atomic mass of the molecule. A water molecule, as you may know, is H2O, and it has an atomic mass of 18. So one mole of water weighs 18 grams. But oxygen gas (two oxygen atoms) has an atomic mass of 32, and so one mole of oxygen gas weighs 32 grams.

In general, one mole of any substance contains Avogadro's Number of molecules or atoms of that substance. Another way of saying that is that 18 grams of water has 6.02 x 10^23 molecules of water, and 32 grams of oxygen gas has 6.02 x 10^23 molecules of oxygen gas.


On this day in chemistry history....

On October 23, 1803...
Chemist John Dalton read aloud to the Manchester Literary and Philosophical Society his essay about how water absorbs gases, and he gave atomic weights for 21 different elements and compounds. From this work on absorption of gases and atomic weights, Dalton came up with a much of the modern atomic theory eventually adopted by physics.

A very appropriate essay to have read on Mole Day!

To learn more about Mole Day, and to find links to a funny song and official website, check out last year's post!


By the way, did you notice...?

National Mole Day has nothing to do with moles-the-mammals-that-dig?