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Topic: Aluminum Oxide  (Read 15889 times)

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Offline Enceph

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Re: Aluminum Oxide
« Reply #15 on: January 03, 2008, 08:44:27 AM »
Argh it was that simple.

Thanks guys, you've been a great help as always  :)

Offline AWK

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Re: Aluminum Oxide
« Reply #16 on: January 03, 2008, 09:17:27 AM »
AWK

Offline Alpha-Omega

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Re: Aluminum Oxide
« Reply #17 on: January 03, 2008, 12:14:37 PM »
You do understand that that picture ....UMMMM...those oxygens are in agony...RIGHT??

The Al forms octahedrals with those oxygens....this is a crystal...This is Al2O3...commonly known as corundum/alumina/bauxite (depends on the production process-See bayer process)...Corundum is also sapphire...many jewels are made of corundum:  sapphire, ruby, etc...they are crystals....they bonding in the d-shells gives them their color properties...

Corundum has many uses...it is also a common polishing agent...so there are different grades...so therir are different crystals...

there is alpha and gamma...now the alpha is an octahedral arrangement of the Al with the oxyges surrounding the Al atoms and this is all packed into a crystal structure called HCP....(hexagonal close packed arrangement). 

Additionally there are layers...the structure is layered..

The gamma version is missing some Al....has what is called a spinal structure...and the missing Al atoms cause what are called DEFECTS (technical term-intersticial sites)  they are basically weaknesses in the structure and slip planes can develop at those points....and that does not mean they are BAD crystals...they have uses....and sometimes thos slip planes can be very useful....

OK probably too much for you....but you earned something....http://en.wikipedia.org/wiki/Al2O3

Offline Enceph

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Re: Aluminum Oxide
« Reply #18 on: January 05, 2008, 08:25:08 PM »
'Write the balanced chemical equation for the reaction between iron (its ion is Fe3+) and oxygen.

7 elements occur as diatomic molecules in their natural states

H2, N2, O2, F2, Cl2, Br2, I2

Its helpful to remember these

Is there any 'rule' I can follow to determine their natural state?  Because my sources just state so and so element is diatomic in it's natural state, mainly halogens, etc.  It doesn't tell me how I can determine this though without individually looking on Google, for the natural state of each element.

Offline LQ43

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Re: Aluminum Oxide
« Reply #19 on: January 05, 2008, 09:01:41 PM »
Those 7 elements are the only elements that are diatomic in their natural state (that's not so many to remember is it?) - they just like to pair up and are more stable that way than by individual atoms

all other elements are written by themselves, e.g   Mg,   Ar,  Li,  Fe 

this http://www.webelements.com/ is pretty useful for lots of information


for states of matter

these elements are gases:

H2, O2, N2, F2, Cl2, all noble gases (Group VIII / 18  )

liquids:

Hg and Br2

solids:

everything else

I would take a nice white periodic table (see attached) and use different colors to highlight in those elements that are diatomic, are gases, liquids and solids  and anything else that is useful regarding periodic trends


Offline Alpha-Omega

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Re: Aluminum Oxide
« Reply #20 on: January 05, 2008, 09:02:54 PM »
OK....I have this feeling that the confusion comes from the words DIATOMIC.  YES all those species occur in nature as diatomic molecules...DIATOMIC does NOT mean they have double bonds....

In nature, chemical elements are often occur as individual atoms, which are also known as monatomic molecules.
 
However, many elements appear as diatomic molecules, as a result of attraction between individual atoms. For example, many gases, such as hydrogen, oxygen, and nitrogen appear as diatomic molecules (H2, O2, N2, F2, Cl2, Br2, etc...).

OK this is one of the best pictures for showing the actuals bonds for most of the aforementioned species:  Note the triple bond for N2....note the single bond for H2 and Cl2...

http://www.mikeblaber.org/oldwine/chm1045/notes/Bonding/Covalent/Bond04.htm

This link shows the double bonds in O2 (nice explains the resoance in O3 too):  

http://en.wikipedia.org/wiki/Oxygen#Structure

I am not sure if you are familiar with MO Theory.   Here is a link to Diatomic Species by MO Theory:
 
http://www.meta-synthesis.com/webbook/39_diatomics/diatomics.html

The creation of a diatomic molecule is a process: two atoms first approach each other; the atoms= outer orbital(s) then converge to create molecular orbitals. Thus, in order to create a H2, the simplest molecule (because hydrogen is the simplest atom), two hydrogen atoms combine there single orbitals into a molecular orbital. Diatomic molecules have two basic types of orbitals. For example, when, in the hydrogen molecule, the values of the two atomic orbitals are added, the resulting molecular orbital, also known as a bonding orbital, occurs in the area between the nuclei. When, however, the value of one atomic orbital is subtracted from the other, the resulting molecular orbital, with a value of almost zero, occurs in other areas than the space between two nuclei. This particular orbital is characterized as anti-bonding.

The formation process is more complex when an atom has more than one orbital. For example, when two lithium atoms (atomic number 3, two orbitals) start forming a Li2 molecule, only the outer orbitals of each atom connect, creating two molecular orbitals (bonding and anti-bonding). It is important to note that an outer orbitals of one atom will not interact with the other atom=s inner orbital. Particular orbitals differ greatly in energy, and only similar orbitals will interact.

Diatomic molecules such as H2 or Li2 are known as homonuclear: they consist of two identical nuclei. Heteronuclear diatomic molecules, exemplified by carbon monoxide (CO) contain two different nuclei. As in the simplest homonuclear diatomic molecules, orbital interaction leads to molecule formation, except that the process is more intricate, given the variety of orbitals.

Heteronuclear diatomic molecules are also represented by a number of salts, including table salt, or sodium chloride (NaCl), potassium iodide (KI), and lithium bromide (LiBr). These particular salts are compounds of an alkali metal and a halogen (the term halogen, a derivation from Greek, conveys the idea of creating salt).


Offline Alpha-Omega

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Re: Aluminum Oxide
« Reply #21 on: January 05, 2008, 09:07:20 PM »
You have been asking me about the bonding right?   I want to make sure I understand your question....just  because they are diatomic does not mean the bonds are double bonds....and this goes back to the N2 problem...N2 is a diatomic molecule but it has a TRIPLE BOND...not a double bond.

This is the distinction I was driving at.....F2 is a diatomic molecule with a single bond...O2 is a diatomic molcule wit a double bond...I hope those links help...

Offline Enceph

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Re: Aluminum Oxide
« Reply #22 on: January 05, 2008, 11:19:36 PM »
I think my questions have been answered, so essentially those seven elements almost immediately attract to each other to form diatomic molecules?

Offline Alpha-Omega

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Re: Aluminum Oxide
« Reply #23 on: January 05, 2008, 11:38:19 PM »
At STP the elements you refer to occur as diatomics molecules.

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