Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Enceph on January 02, 2008, 01:33:05 PM
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An element like Aluminum that has 3 valence electrons, can only get a maximum of 6 valence electrons through sharing with other atoms right?
Or since Aluminum needs 5 electrons to fill a full valence shield of 8, can it be 'given' electrons from other atoms, that are not being shared?
Because at the moment it kind of looks like this,
(in attachment), I know that some of the lines are crooked, but it was a quick paint job.
There are still 2 electrons spots left in each Aluminum electron, does that mean that this bond does not work? In my book it would appear that it does. Or do these two Aluminum atoms stay at 6/8 in their valence shell?
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OH MY...that is very CREATIVE...let me think a little...you drew that youself...with paint????
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i think he means with microsoft paint... on the computer. :)
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Aluminum oxide, aka alumina, is a difficult "molecule" to determine structurally. If you go to Wiki, or the a chemical distributor's database, you will get the general formula Al2O3. This general formula is used because it allows for charge balance, the Aluminum gives up 3 electrons (easier than acquiring 5), and the Oxygen receives 2 electrons (easier than giving up 6). But as far as a discrete molecular structure goes, I don't think there is one in this case. I seem to recall that since Aluminum is close to the semimetals in the periodic table its oxides may be similar. Silicon dioxide (SiO2) does not have a discrete molecular structure, the chemical formula is just used to represent a large matrix or network of bonded atoms. In fact, I believe that aluminum is one of the metals used to dope or modify silicon semiconductors. Your proposed molecule is very creative, but think of all those poor oxygen atoms with six bonds to them. Oxygen atoms generally only like having 2 bonds (water), or three if they are positively charged. I hope this helps you understand what is going on here and if you have further questions don't hesitate to ask.
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Yes good job with PAINT...use it all the time...OK:
Al2O3 (2 Al’s gives total of 6 e–‘s to 3 O’s to form 2Al3+ and 3O2–)
The geometry is octahedral.
The bonds are ionic (2 Al3+ cations to 3O2- anions).
Aluminum oxide exists in several different crystallographic forms, of which corundum is most common. Corundum is characterized by a high specific gravity (4.0), a high melting point (about 2,050° C, or 3,700° F), great insolubility, and hardness.
Element: Al ; % Composition: 52.93; Formal Oxidation State: +3 Formal Electronic Structure: [Ne]
Element: O; % Composition: 47.07; Formal Oxidation State: -2 Formal Electronic Structure: [He].2s2.2p6
A Group 3 metal + a Group 6 non-metal e.g. aluminium + oxygen ==> aluminium oxide Al2O3 or ionic formula (Al3+)2(O2-)3 In terms of electron arrangement, two aluminium atoms donate their three outer electrons to three oxygen atoms. This results in two triple positive aluminium ions to three double negative oxide ions. All the ions have the stable electronic structure of neon 2.8. Valencies, Al 3 and O 2.
2Al (2.8.3) + 3O (2.6) ==> 2Al3+(2.8) 3O2- (2.8)
can be summarized electronically as 2[2,8,3] + 3[2,6] ==> [2,8]3+2 [2,8]2-3
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Let me try sending that diagram again
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OK see attached document...should have dot structures...
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Wow the forum sure is fast today!
As always great, detailed help. :)
Can someone though please answer this,
In this equation,
4Fe+3O2 -> 2Fe2O3
With Fe3+ and O2- as the molecules in question. Why
does Oxygen (O) keep its subscript (2, before the reaction),
and Fe does not keep it's subscript (3, before the reaction)?
After the reaction it shows the subscripts that are produced, but
before the reaction it keeps Oxygen's prereaction subscript, but
does not show Fe's. I understand that 4Fe3 wouldn't work, but you
aren't able to change the subscript in a formula.
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Really, looks like O2 in reactants and O3 in products to me...TYPO perhaps????
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Really, looks like O2 in reactants and O3 in products to me...
Yep that is correct.
Why is it like this though? Where it shows Oxygen's reactant subscript, but doesn't show Iron's reactant subscript, but then shows their product subscripts.
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You have got to phrase those questions more clearly....you distincly ask why the subscripts for O do not change...Here are your words:
4Fe+3O2 -> 2Fe2O3
With Fe3+ and O2- as the molecules in question.
Why does Oxygen (O) keep its subscript (2, before the reaction),and Fe does not keep it's subscript (3, before the reaction)?
After the reaction it shows the subscripts that are produced, but before the reaction it keeps Oxygen's prereaction subscript, but does not show Fe's. I understand that 4Fe3 wouldn't work, but you
aren't able to change the subscript in a formula.
I understand that 4Fe3 wouldn't work, but you aren't able to change the subscript in a formula.
Now by prereaction am guessing you mean reactants or are you talking about the coefficient in front of the Fe???
Ok I am not seeing any of that in that equation...
4 Fe.... in reactants and get 2Fe2 in products ....charges balanced...right?? 4 = 2 x2 both sides equal right!!!!!!!!
Now O in reactant = 3 x 2 = 6 right....right!!!!!!!! and if I go to products...that 2 in front of the Fe is also associated with the O3....so 2 x 3 = 6 and so if 3 x 2 = 6 and 2 x 3 = 6....then we are all balanced right??????
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Wow the forum sure is fast today!
As always great, detailed help. :)
Can someone though please answer this,
In this equation,
4Fe+3O2 -> 2Fe2O3
With Fe3+ and O2- as the molecules in question. Why
does Oxygen (O) keep its subscript (2, before the reaction),
and Fe does not keep it's subscript (3, before the reaction)?
After the reaction it shows the subscripts that are produced, but
before the reaction it keeps Oxygen's prereaction subscript, but
does not show Fe's. I understand that 4Fe3 wouldn't work, but you
aren't able to change the subscript in a formula.
Fe3+ does not have a subscript, the 3+ is a superscript meaning charge 3+
same with the O2- that is the superscript meaning charge 2-
however, that is all irrelevant.
Fe + O2 before the reaction have NO charges, they are neutral and are elements
O2 means diatomic oxygen with this 2 as a subscript
when they react in this redox reaction, electrons are transferred from Fe to O and to make the product Fe2O3
now , after the reaction in the product, Fe is Fe3+ and O is O2-
with the proper subscripts is the balanced equation
4Fe + 3O2 --> 2Fe2O3
it takes a bit of time getting used to seeing all these without the sub and superscripts just because we all are too lazy to put them in.
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Is that what you were asking????
4 moles of elemental iron react with 3 moles of O2 gas (oxygen is diatomic in its natural state) react to form 2 moles of Fe2O3...and it is all balanced....OK yes the charges are not usually written into the reaction equation...and ther has to be a charge and mass balance....the charges are usually assumed....well, bad choice of words...you can figure them out from state....
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Is that what you were asking????
Yeah pretty much.
So the diatomic oxygen, is a molecule with two oxygen atoms? (my question only refers to oxygen)
But how would I be able to tell that there are two oxygen atoms when putting together the equation, if all it asks me is
'Write the balanced chemical equation for the reaction between iron (its ion is Fe3+) and oxygen.
I understand how the product side works, the Fe2, O3. But I still do not see how I can know that it would be Fe, and O2 on the reactant side. (I was aware of the correct equation for the product side)
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'Write the balanced chemical equation for the reaction between iron (its ion is Fe3+) and oxygen.
Interpreting questions can be tricky (as we have seen). The two elements are given and the question assumes you know what their natural states are.
7 elements occur as diatomic molecules in their natural states
H2, N2, O2, F2, Cl2, Br2, I2
Its helpful to remember these
Fe3+ is given so that you will know what the charge on the iron will be in the product
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Argh it was that simple.
Thanks guys, you've been a great help as always :)
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http://phycomp.technion.ac.il/~ira/types.html#Al2O3
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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
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'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.
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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/ (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
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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).
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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...
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I think my questions have been answered, so essentially those seven elements almost immediately attract to each other to form diatomic molecules?
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At STP the elements you refer to occur as diatomics molecules.