Free Republic
Browse · Search
News/Activism
Topics · Post Article

Skip to comments.

Atomic weights of 10 elements on periodic table about to make an historic change
Eureka Alert ^ | 15 Dec 2010 | Leanne Yohemas

Posted on 12/15/2010 5:23:20 PM PST by smokingfrog

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.

The new table, outlined in a report released this month, will express atomic weights of 10 elements - hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine and thallium - in a new manner that will reflect more accurately how these elements are found in nature.

"For more than a century and a half, many were taught to use standard atomic weights — a single value — found on the inside cover of chemistry textbooks and on the periodic table of the elements. As technology improved, we have discovered that the numbers on our chart are not as static as we have previously believed," says Dr. Michael Wieser, an associate professor at the University of Calgary, who serves as secretary of the International Union of Pure and Applied Chemistry's (IUPAC) Commission on Isotopic Abundances and Atomic Weights. This organization oversees the evaluation and dissemination of atomic-weight values.

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.

(Excerpt) Read more at eurekalert.org ...


TOPICS: Canada; News/Current Events
KEYWORDS: chemistry; elements; science
Navigation: use the links below to view more comments.
first previous 1-20 ... 61-8081-100101-120 ... 141-147 next last
To: Hoodat

“I take it that you have never taken a quantitative analysis class. The 35.453 is the most important number because if you have one mole of chlorine gas, it will weigh 70.906 grams. Not 70 grams. Not 74 grams. But 70.906 grams.”

Yep sure have. Have you ever had to determine that number experimentally? It’s quite revealing.


81 posted on 12/15/2010 9:05:46 PM PST by BenKenobi (Obama's book of the month, Herman Melville's Killin' Whitey)
[ Post Reply | Private Reply | To 78 | View Replies]

To: tubebender
My only experience with chemistry came in the spiffy little kit I got one Christmas many many years ago but this statement jumped out at me... the atomic weight of carbon in natural human testosterone is higher than that in pharmaceutical testosterone.

One wonders what chemical processes can bring that about (although I for one don't wonder too awfully hard).

82 posted on 12/15/2010 9:07:24 PM PST by Erasmus (Personal goal: Have a bigger carbon footprint than Tony Robbins.)
[ Post Reply | Private Reply | To 12 | View Replies]

To: SeeSac

One, Mass and weight aren’t the same thing.

Two Relative atomic mass is the mass of the ratio of CL 35- CL 37. It has no meaning outside of the expected ratio which can very significantly.


83 posted on 12/15/2010 9:08:01 PM PST by BenKenobi (Obama's book of the month, Herman Melville's Killin' Whitey)
[ Post Reply | Private Reply | To 79 | View Replies]

To: BenKenobi

Try 20.


84 posted on 12/15/2010 9:08:29 PM PST by Hoodat (Yet in all these things we are more than conquerors through Him who loved us. - (Rom 8:37))
[ Post Reply | Private Reply | To 80 | View Replies]

To: BenKenobi

Edit, 20, sorry.


85 posted on 12/15/2010 9:08:34 PM PST by BenKenobi (Obama's book of the month, Herman Melville's Killin' Whitey)
[ Post Reply | Private Reply | To 80 | View Replies]

To: Hoodat

Hard enough replying to two people at a time.


86 posted on 12/15/2010 9:10:11 PM PST by BenKenobi (Obama's book of the month, Herman Melville's Killin' Whitey)
[ Post Reply | Private Reply | To 84 | View Replies]

To: BenKenobi
You: Wrong. You fail chemistry. The atomic mass of CL 35 is 35.453 as a result of CL 35 having 17 protons and 18 neutrons.

If so (if those were your words), you are incorrect. It is because it is a mixture of 35CL and 37CL and is a result of CL 35 having 17 protons and 18 neutrons CL 37 having 17 protons and ____ neutrons. I will let you fill in the blank”

Relative atomic mass has nothing to do with the actual properties of Chlorine. This is why it shouldn’t be on a periodic table.

Forget the periodic table for one minute and address the error you made that I was pointing out to you. If you just take one minute and google chlorine atomic weight you will see that your 35.423 is a result of a mixture of two isotopes.

87 posted on 12/15/2010 9:10:19 PM PST by SeeSac
[ Post Reply | Private Reply | To 80 | View Replies]

To: neverdem

In case you missed this... ping


88 posted on 12/15/2010 9:11:03 PM PST by Gene Eric (Your Hope has been redistributed. Here's your Change.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: smokingfrog
Hmmmm....Revisionism in it's purest sense...

First global warming...Now this...

Wonder if I can get a partial refund on the $65 I spent on a high-grade diamond engagement ring 53-years ago?

89 posted on 12/15/2010 9:11:14 PM PST by SuperLuminal (Where is another agitator for republicanism like Sam Adams when we need him?)
[ Post Reply | Private Reply | To 1 | View Replies]

To: BenKenobi
Yep sure have. Have you ever had to determine that number experimentally? It’s quite revealing.

How did you go about doing it? Did you count the number of molecules?

90 posted on 12/15/2010 9:11:18 PM PST by Hoodat (Yet in all these things we are more than conquerors through Him who loved us. - (Rom 8:37))
[ Post Reply | Private Reply | To 81 | View Replies]

To: BenKenobi

Take it up with the IUPAC. I am done with you and your refusal to go google Chlorine.

The IUPAC definition of atomic weight is:

An atomic weight (relative atomic mass) of an element from a specified source is the ratio of the average mass per atom of the element to 1/12 of the mass of an atom of 12C.


91 posted on 12/15/2010 9:14:33 PM PST by SeeSac
[ Post Reply | Private Reply | To 83 | View Replies]

To: Hoodat
How did you go about doing it? Did you count the number of molecules?

I am done. Have fun.

92 posted on 12/15/2010 9:15:45 PM PST by SeeSac
[ Post Reply | Private Reply | To 90 | View Replies]

To: SeeSac

*Sigh*

“You make some outrageous attack”

And you are being sweetness and light? Great, solid attitude here.

Relative atomic mass is not an intrinsic elemental property. It’s misleading. It assumes experimentally derived information which may or may not be the case with the actual sample.

It’s not universally applicable, and there are many applications for which it is not useful at all. This is why periodic tables should state the mass of the most common isotope which is true no matter what sample you use or how you go about doing things. Why? Because it’s related to the intrinsic characteristics of the element, the neutrons, protons and electrons. It’s not reliant upon ‘expected ratio in nature’, which isn’t always the case.


93 posted on 12/15/2010 9:16:51 PM PST by BenKenobi (Obama's book of the month, Herman Melville's Killin' Whitey)
[ Post Reply | Private Reply | To 77 | View Replies]

To: SuperLuminal
Hmmmm....Revisionism in it's purest sense...

No revisionism. All they are doing is instead of stating a single number with uncertainties based on varying isotopic rations, they are specifying a range of values based on varying isotopic rations. SAME-SAME. Just in a different view.

94 posted on 12/15/2010 9:17:46 PM PST by SeeSac
[ Post Reply | Private Reply | To 89 | View Replies]

To: SeeSac

“An atomic weight (relative atomic mass) of an element from a specified source is the ratio of the “average mass per atom of the element to 1/12 of the mass of an atom of 12C.”

Which is not the definition that you are using here.

Thank you for quoting this.


95 posted on 12/15/2010 9:18:07 PM PST by BenKenobi (Obama's book of the month, Herman Melville's Killin' Whitey)
[ Post Reply | Private Reply | To 91 | View Replies]

To: Aevery_Freeman
From the OP:

an atomic mass unit or amu is one twelfth of the mass of an unbound atom of carbon-12

This does not take into account any mass defect inherent in the stability of a nuclei. It also assumes an isotopic mixture which may vary from sample to sample.

Well, they do say Carbon 12.

But a couple things here surprised me.

For one thing, I didn't know that they took the whole atom, protons, neutrons, electrons, muons, etc., and all.

And because of the packing defecit which you mention, it apparently means that a single free atom of hydrogen (not D or T) will not have a mass of exactly 1 AMU.

So today wasn't a total waste, since I learnt something--with 1 whole minute to go (in my timezone).

(Wot's with FR's clock, anyway? I guess they're using a Cesium standard based on the old weights.)

96 posted on 12/15/2010 9:18:18 PM PST by Erasmus (Personal goal: Have a bigger carbon footprint than Tony Robbins.)
[ Post Reply | Private Reply | To 13 | View Replies]

To: SeeSac
Aw, don't quit now. I was in the middle of calculating how many 'extra' electrons a 35Cl atom would need to bump it's weight mass up to 35.453 - lol!

But seriously, I'm done too. It really isn't worth it.

97 posted on 12/15/2010 9:19:56 PM PST by Hoodat (Yet in all these things we are more than conquerors through Him who loved us. - (Rom 8:37))
[ Post Reply | Private Reply | To 92 | View Replies]

To: SeeSac

“No revisionism. All they are doing is instead of stating a single number with uncertainties based on varying isotopic rations, they are specifying a range of values based on varying isotopic rations. SAME-SAME. Just in a different view.”

Not the same at all. Big, big difference. The old definition has the atomic mass of every element as a ratio of C-12. Now, this is no longer the case. Which is exactly the point I was trying to hammer home earlier.

The relative abundances of each element is irrelevant.


98 posted on 12/15/2010 9:20:25 PM PST by BenKenobi (Obama's book of the month, Herman Melville's Killin' Whitey)
[ Post Reply | Private Reply | To 94 | View Replies]

To: Mikey_1962
Many moons ago, an office mate of mine was into "zero" jokes. Here's one he came up with:

Ahmed: "Shazam! I've just discovered zero!"

Ali: "What's that?"

Ahmed: "Oh, nothing."

99 posted on 12/15/2010 9:22:30 PM PST by Erasmus (Personal goal: Have a bigger carbon footprint than Tony Robbins.)
[ Post Reply | Private Reply | To 15 | View Replies]

To: Erasmus

“And because of the packing defecit which you mention, it apparently means that a single free atom of hydrogen (not D or T) will not have a mass of exactly 1 AMU.”

Yep, you’ve got it perfectly.

That’s how it worked under the old system. Under the new system, this fact is no longer relevant. Sad, eh?


100 posted on 12/15/2010 9:23:06 PM PST by BenKenobi (Obama's book of the month, Herman Melville's Killin' Whitey)
[ Post Reply | Private Reply | To 96 | View Replies]


Navigation: use the links below to view more comments.
first previous 1-20 ... 61-8081-100101-120 ... 141-147 next last

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
News/Activism
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson