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Everything you've ever known is wrong (periodic tablewise)

Doctor Q

Doctor Q

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Sep 19, 2002
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News story
For the first time in history, a change will be made to the atomic weights of some elements listed on the periodic table of the chemical elements posted on walls of chemistry classrooms and on the inside covers of chemistry textbooks worldwide.

Modern analytical techniques can measure the atomic weight of many elements precisely, and these small variations in an element’s atomic weight are important in research and industry. For example, precise measurements of the abundances of isotopes of carbon can be used to determine purity and source of food, such as vanilla and honey. Isotopic measurements of nitrogen, chlorine and other elements are used for tracing pollutants in streams and groundwater. In sports doping investigations, performance-enhancing testosterone can be identified in the human body because the atomic weight of carbon in natural human testosterone is higher than that in pharmaceutical testosterone.​

The bottom line: The atomic weights of hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine and thallium will be expressed as ranges instead of single values.

Will chemistry class get even harder now?
 
For example, sulfur is commonly known to have a standard atomic weight of 32.065. However, its actual atomic weight can be anywhere between 32.059 and 32.076, depending on where the element is found. “In other words, knowing the atomic weight can be used to decode the origins and the history of a particular element in nature,” says co-author Wieser of the Department of Physics and Astronomy.​
If you do computations using an atomic weight I guess you have to average the values and use the center of the range, unless you know which atomic weight applies to the element in the situation you are dealing with.

But I think I'll just round off to an integer!
 
Honestly I'm surprised that's news, I recall being taught that atomic weights were approximations.

Cool :)
 
I wonder how many people this helps, and how many people this hurts?

Sometimes, finding a more accurate way to do something won't help someone. If thresholds were set due to years of scientific experiments, analysis, and observations, changing the atomic weights won't do them any good, particularly if they make decisions based on threshold values. Sure, I suppose you could scale all your thresholds by the %change in atomic weight. However, it gets tricky when some people may do careful analysis using the "range" of atomic weights introduced for some elements, while others may just use the average value in the range (or most probable weight).
 
My teachers always taught me that they were an average of all the isotopes of the given element. :confused:

I wonder if my hard-headed AP Chemistry teacher right now would use this new format for the rest of the year, or the old format. :rolleyes:
 
fireshot91 said:
My teachers always taught me that they were an average of all the isotopes of the given element. :confused:

I wonder if my hard-headed AP Chemistry teacher right now would use this new format for the rest of the year, or the old format. :rolleyes:
Click to expand...

Most likely schools will continue to use the old format for a few more years. For instance you would be worried at how many schools STILL teach that Pluto is a planet.

Their usual explanation is that "for all intents and purposes it is still accurate"
 
Dalton63841 said:
Most likely schools will continue to use the old format for a few more years. For instance you would be worried at how many schools STILL teach that Pluto is a planet.

Their usual explanation is that "for all intents and purposes it is still accurate"
Click to expand...

I wish the only thing we had to worry about in our schools was whether they are teaching Pluto is a planet or not
I can't say that worries me at all
 
This has always been known... I'm not quite sure how its news.

Of course the mass is exact or finite; the current atomic mass is just the average of all isotopes, however in order to be truly accurate they'd need to use a confidence interval. Regardless this won't effect much at all-- relatives are almost always used as a "good enough" approximation. For required calculations the current atomic mass will continue to be used, such as Pchem, because it's still the best fit unless you also choose to calculate the confidence interval for your equation. The only people this will really effect is computational chemists and certain sub molecular physicists; everyone else will still use general approximations (for a wide variety of reasons).
 
Now this whole ranges thing will be a pain, only 1 more year of school before uni for me so I do not think they will alter it in the syllabus this year. But when it comes time for uni it will be fun...
 
I'm happy that I'm in my senior year in high school and this won't be in syllabus till next year (at the earliest)...AP Chem is hard enough...maybe I'll have to take it again in college :eek:
 
I always thought that those values were just the average of all of the isotopes, was I wrong, or are they just deciding that they should teach all of the values that they used to use for those averages?
Dalton63841 said:
Agreed! Without Pluto, what did My Very Educated Mother Just Serve Us? Noodles maybe? That sucks.
Click to expand...

I like the one that the astronomer who murdered Pluto came up with for the eight planets "Mean Very Evil Men Just Shortened Up Nature"
 
Heck, when I was in school, there were only 4 oceans. How did we just create another ocean? I think it should be the Loop ocean...since it loops around Antarctica.

GL
 
fireshot91 said:
My teachers always taught me that they were an average of all the isotopes of the given element. :confused:

I wonder if my hard-headed AP Chemistry teacher right now would use this new format for the rest of the year, or the old format. :rolleyes:
Click to expand...

even in this new format it still would be. Just the average changes depending on the location where you get the element. That really has not changed.


Now that being said I am going to ask who really uses any of that information any more. I have a fair amount of chemistry under my belt (both college and HS) and chances are I will not be using it much at all. Only real reason in the future I see myself using is to help my future kids in chemistry class. Out side of that not a real chance. I have my little more than a basic understanding of the information and do think it is a good core class.
 
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