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ultimateboy
25th December 2008 - 07:35 AM
I want an article on lewis dot structure of about 12 to 15 pages.
I had tried on many sites but they had small package of information.
If you know any link of encyclopedic site then give me.
griann
13th January 2009 - 10:23 AM
exam or report due?
TracerTong
11th February 2009 - 12:18 AM
Diagram:http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/perlewis.html
wikipedia:http://en.wikipedia.org/wiki/Lewis_structure
Open courseware(search): http://ocw.mit.edu/OcwWeb/Chemistry/index.htm
Trippy
20th February 2009 - 12:58 AM
QUOTE (Cusa+Feb 20 2009, 01:29 PM)
Avogadro couldn't count his Mole. In history he never knew how many atoms there are in anything. He couldn't weigh the individual atom.

Now we can but Avogadro couldn't.

Mitch Raemsch

Learn some History.

Amadeo Avogadro proposed in 1811 that "The volume of a gas at a given temperature and pressure is proportional to the number of Atoms or molecules regardless of the nature of the gas".
Johann Loschmidt indicated the value of this constant in 1865 (done by estimating the diameter of the molecules in air).
Jean Perrin proposed in 1909 that we name it after Avogadro, and won the 1926 Nobel Prize for his work in determining the value of avogadro's number (or it was one of the reasons anyway).

In short? Avogadro didn't try and count the mole, nor did he need to because it was proposed as a hypothesis that was later verified, and wasn't proposed using the language that is now used to define it.

English translation of Avogadros 1811 paper in which he proposes the idea

The 1909 paper in which Jean Perrin proposes the name for the idea

Presentation speech for the 1926 Nobel Prize in Physics
Trippy
20th February 2009 - 01:34 AM
QUOTE (Cusa+Feb 20 2009, 02:07 PM)
He didn't know atomic weights.

Actually, they did - it's simple enough to find, you just need the charge to mass ratio which can be derived from a magnetic field of known strength and the amount of deflection of a beam of ions.

And just to prove you further wrong - Mendleev's periodic table released in 1869 was ordered by Atomic Mass, and if you had bothered reading the links I kindly took the time to provide you with, you would see that in his original paper (the 1811 one I linked to) you would see that he referred directly to atomic masses.

In fact John Dalton in 1805 published the first table of atomic weights, based on stoichiometric proportions, and defining Hydrogen as being 1. By the time of teh Karlsruhe Congress in 1860, the accuracy of these measurements had been refined to a relative accuracy of about 1%, and many of the unknown stoichiometries had been resolved.

So again, you are quite simply, wrong.
Trippy
20th February 2009 - 02:03 AM
QUOTE (Cusa+Feb 20 2009, 02:56 PM)
How did they know electron mass? neutron mass? and proton mass?
How did they know how many neutrons by weight?
These would be a requirement.

You don't need to know the absolute mass, only the relative mass.
Trippy
20th February 2009 - 02:22 AM
QUOTE (Cusa+Feb 20 2009, 03:05 PM)
I don't believe that.

Absolute mass is required.

The AMU is a relative mass, not an absolute mass.
When we say that Oxygen has an Atomic weight of 16, we really mean that it has a mass of 16 atomic mass units.

The mole, which involves avogadros number is simply a unit to make converting between a relative mass and an absolute mass easier.

We know that if we define Hydrogen-1 as weighing 1 AMU, then Carbon 12 weighs 12 AMU. Avogadros number is simply the number required to convert from 12 AMU to 12 grams. But there is no requirement to know the absolute mass of a proton in order to develop the concept

It's just the same as saying "Carbon is 12 times heavier than Hydrogen, so how many atoms of Carbon are required to make 12 (Oz/g/lb/kg) of Carbon.

Get over it, you're wrong, you simply haven't understood that you're wrong (or why you're wrong) yet.
Trippy
20th February 2009 - 02:55 AM
QUOTE (Cusa+Feb 20 2009, 03:40 PM)
How do you measure mass of Hydrogen?
How many hydrogen atoms are there?

Mitch Raemsch

Irrelevant when considering Relative atomic mass, it is (in this case) defined as being 1.

Dalton did his calculations based on the volumes of the atoms (how he arrived at that I don't know), you'll have to ask him (might be difficult on account of a slight case of rigormortis, compounded by decomposition).

I know that Dalton did a lot of work with the vapour pressure of liquids.

Berzelius also worked a lot with vapor pressures, and compiled his own list, with Oxygen having a mass of 100, and the mass of other elements being relative to that.

As I said.

Atomic mass, and Atomic Mass Units are relative, not asbolute measures.
rpenner
20th February 2009 - 03:07 AM
No. Lewis dot structure is what we are talking about here. Six posts deleted.
Cusa
20th February 2009 - 03:10 AM
QUOTE (rpenner+Feb 20 2009, 03:07 AM)
No. Lewis dot structure is what we are talking about here. Six posts deleted.

Maybe we should move this to another thread.

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