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AuthorTopic: Someone remind me how chemical notation works again...  (Read 2408 times)

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Offline odin

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Someone remind me how chemical notation works again...
« on: February 25, 2004, 10:14:22 PM »
I know the basic CO2 notation is two O's glued to one C. But what is it again with superscript number after the atom letter. Electron surplus of deficiency? And what about isotopes? isn't that a subscript number in front of the letter? Or something?

Five years since having had the last chemistry has killed my knowledge quite a bit it seems :-).

Offline Speelgoedmannetje

Re: Someone remind me how chemical notation works again...
« Reply #1 on: February 25, 2004, 10:20:47 PM »
hm, yes, it is seven years ago or so when I did such the last time. It is subscribt, the 2 by the CO2.
naah, for the rest, I've forgotten it :-(
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Offline odin

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Re: Someone remind me how chemical notation works again...
« Reply #2 on: February 25, 2004, 10:22:58 PM »
Chemistry almost killed my final exams. I needed a 3½ and that was exactly what I got on my chemistry exam :-).

Offline bloodline

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Re: Someone remind me how chemical notation works again...
« Reply #3 on: February 25, 2004, 10:26:12 PM »
when you are looking at the Elemental symbol the numers in front are the Atomic number and the Atomic Mass.

The Atomic number is the number of Protons
The Atomic mass is the number of protons and Neutrons

The Atomic number IS the element, all have unique numbers.

The Atomic mass defines the Isotope. (This number is ALWAYS bigger than the Atomic number)

Offline Speelgoedmannetje

Re: Someone remind me how chemical notation works again...
« Reply #4 on: February 25, 2004, 10:26:34 PM »
Quote

odin wrote:
Chemistry almost killed my final exams. I needed a 3½ and that was exactly what I got on my chemistry exam :-).
:lol:
Chemistry almost SAVED my exam, if maths didn't brutally kill it :-(
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Re: Someone remind me how chemical notation works again...
« Reply #5 on: February 25, 2004, 10:30:01 PM »
Quote

odin wrote:
I know the basic CO2 notation is two O's glued to one C. But what is it again with superscript number after the atom letter. Electron surplus of deficiency? And what about isotopes? isn't that a subscript number in front of the letter? Or something?

Five years since having had the last chemistry has killed my knowledge quite a bit it seems :-).


Oh yeah, the Superscript after the Letter is the Charge on the ion.

Offline T_Bone

Re: Someone remind me how chemical notation works again...
« Reply #6 on: February 25, 2004, 10:30:12 PM »
Notation? What the...?

Look, everything is made out of four elements
Air, Water, Earth, and Fire. ;-)
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Re: Someone remind me how chemical notation works again...
« Reply #7 on: February 25, 2004, 10:33:14 PM »
Quote

T_Bone wrote:
Notation? What the...?

Look, everything is made out of four elements
Air, Water, Earth, and Fire. ;-)


you forgot Wind... and Death... :-D

Offline KennyR

Re: Someone remind me how chemical notation works again...
« Reply #8 on: February 25, 2004, 10:52:37 PM »
Isotope (atomic weight) is superscript, right of the symbol.

Protons in the nucleus is superscript, left of the symbol (not often used).

Number of atoms of the element present is subscript, right of the symbol.

For example, U238 (superscript, damn ascii), is the isotope of Uranium with atomic mass of 238.
 

Offline Speelgoedmannetje

Re: Someone remind me how chemical notation works again...
« Reply #9 on: February 25, 2004, 10:57:28 PM »
a :pint: to KennyR!
And what was it again left subscribt?
That was something hardly used or so, but what was it again :-?
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Offline KennyR

Re: Someone remind me how chemical notation works again...
« Reply #10 on: February 25, 2004, 11:09:42 PM »
Maybe subscript left is neutrons in the nucleus, but I've almost never seen it used (once you have the atomic mass and the number of protons, you can just subtract and get the neutrons). And neutrons don't have any effect on chemistry.
 

Offline Speelgoedmannetje

Re: Someone remind me how chemical notation works again...
« Reply #11 on: February 25, 2004, 11:16:25 PM »
Quote

KennyR wrote:
(once you have the atomic mass and the number of protons, you can just subtract and get the neutrons)
I know, but I rather think it was something with radiation or so. I've really really forgotten it.
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Re: Someone remind me how chemical notation works again...
« Reply #12 on: February 26, 2004, 10:04:49 AM »
Quote

Speelgoedmannetje wrote:
Quote

KennyR wrote:
(once you have the atomic mass and the number of protons, you can just subtract and get the neutrons)
I know, but I rather think it was something with radiation or so. I've really really forgotten it.


In "nuclear reactions", ie radio active decaty of Uranium 235, one can measure the mass of the resulting nucleus and compare that wit the mass one would expect to get and you end up with a value called the "Mass defect". Using E=MC^2  (where M = the mass defect) one can work out the energy released from the "nuclear reaction"... but this is phisics, and I'm a chemist, so I don't care :crazy:

Offline Cymric

Re: Someone remind me how chemical notation works again...
« Reply #13 on: March 01, 2004, 11:51:32 AM »
Superscript left: total number of nucleons (i.e., number of protons plus number of neutrons); also written in normal font to the right of the chemical symbol (C-14, U-238)

Subscript left: total number of protons (should match the chemical symbol, i.e. ^14_7 C is bogus, as 'C' has 6 protons, not 7)

Superscript right: charge of the ion in electrons, designating a surplus (-) or deficiency (+); OR: number of unpaired electrons in case you're dealing with a radical---but in the latter case you write a dot, not a number

Subscript right: amount of atoms making up the molecule.

Funny things happen in case of nucleons and leptons:
neutron = ^1_0 n
proton = ^1_1 p = ^1_1 H+
electron = ^0_-1 e-
anti-electron = positron = ^0_+1 e+
which seem like notational quirks but are still very useful.

Contrary to popular belief and high school teachings, neutrons *do* have an effect on chemistry, but it's subtle and for all intents and purposes can be ignored. For example, it has been noted that in some reactions involving the transfer of hydrogen atoms, substituting them by their twice as heavy brother atom deuterium slows the reaction rate by over 30%. It has been hypothesised that drinking sufficient amounts of D2O will kill you because of this, but I think the consensus was that you will die from drinking too much water first. (Which, by the way, has actually been reported in medical literature.)
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