10 replies to this topic

[albertlee]

As stated in the topic,

if we have a water molecule, H2O, and the electronegativity for H is 2.1 and O is 3.5, is the attraction of H2 bigger than O???
since 2 times 2.1 is bigger than 3.5!!!

Any help on this??

[Gilded]

I'm quite sure that the two H won't have their electronegativities added together, since electronegativity is specific to each atom, not a bunch of atoms. In fact. I'd imagine that their electronegativity decreases when their electrons are taken over by oxygen.

[albertlee]

Ummm.... very very much more complicated than diatomic covalent bond...

because you can just find the difference of electronegativity of two atoms to know the polarity...

but once it is polyatomic, things get too much complicated..... for example, how to compare the polarity of eg, CH4, and CO2???

[budullewraagh]

you compare the polarity of individual bonds. the C-H bond in methane is slightly polar (according to pauling). the shape is a tetrahedron. as a result you have a bunch of C-H bonds going out in all directions, and thus there are no opposite poles. there are 2 C=O bonds in carbon dioxide. these bonds are both quite polar, but the compound itself is nonpolar because there arent "ends" that are of opposite charges.

[albertlee]

thx bud!!

but how do you know that there are'nt "ends" that are of opposite charge???

and secondly, for CH4, the 4 ends are slightly positive charge, why's that??

Albert

[albertlee]

By the way, if I know all about this, I only know how to find which polyatomic molecule is polar, but not its magnitude...

So, how do I find the magtnitude of negative charge end in a polar molecule??

Albert

[albertlee]

Any body can help???

[budullewraagh]

but how do you know that there are'nt "ends" that are of opposite charge???

and secondly, for CH4, the 4 ends are slightly positive charge, why's that??

the carbon-hydrogen bonds are all equal in bond radius, bond energy, etc, and the polarity is no exception; polarity remains constant in all C-H bonds. the H ends of methane are slightly positive because hydrogen is less electronegative than carbon. as a result, the electrons used in bonding are farther from hydrogen, leaving more positive ends.

By the way, if I know all about this, I only know how to find which polyatomic molecule is polar, but not its magnitude...

So, how do I find the magtnitude of negative charge end in a polar molecule??

it's interesting that you ask that, as i have asked many people on many forums and i still do not know. one thing you can do is look at various reactions. for example, if you heat sulfuric acid and potassium nitrate, you will get nitric acid and potassium sulfate. potassium is a more active cation than hydrogen, so it chooses to go to the sulfate ion, which is more active as an anion than the nitrate anion. if you look at sodium phosphide, it reacts with water forming sodium hydroxide and hydrogen phosphide, because the hydroxide anion is more active than the phosphide. maybe some day i will have the time to figure out a table for these. as of yet, however, i have yet to see an anion more active than the sulfate anion. i also believe that the nitrate anion is second to the sulfate or at least very close.

[albertlee]

thx bud....

Any way, does not matter not to answer my last question....

because I know it involves alot of quatum mechanics......., which takes in many factors to it....

thx again

[budullewraagh]

i have actually looked all over and have never found anything on a polyatomic anionic activity series

[bassamco722]

I read about this equistion too much but and I didn't find an accuret answer. However I think it will be the diffrence between values of electronegativity and it will depend on the geomerical shape of covalent compound and values of elctronegativity of each atom and final charg occure on the molecules