stylusdef Posted December 2, 2007 Report Share Posted December 2, 2007 Ok, so I don't have the best chemistry teacher in the world... Could someone briefly explain what a van der Waals bond/force is? We've written notes during class, and mine say that van der Waal forces appear when vibrating electrons circulate around the nucleus of an atom, because of attractions to another atom. We've also written that "van der Waal bonds hate water." Could someone briefly explain what a hydrogen/dipole bond is? First off I'd like to know if a hydrogen bond is the same as a dipole bond, 'cause I think our teacher said so. The notes we've written say that dipole bonds appear when molecules are attracted to eachother's opposite charges. We've also written that hydrogen bonds love water. So. Please help! Reply Link to post Share on other sites More sharing options...
Ghanem9 Posted December 2, 2007 Report Share Posted December 2, 2007 (edited) from my rusty memory about this subject: Van der waal forces occur instantaneously, as the electrons in one atom orbit th nucleus they reach certain position where they are close to the other atom and at that point a force of attraction occurs. Ima copy what i have written in my copybook: "Van der waal forces of attraction depends on teh size, molar mass and surface area of the non polar covalent molecule. As the size or Mr increases the electrons become less attracted to the nucleus so their random motion increases and the instantaneous polarization increases and so does the van der waal forces" As for the hydrogen bond, it is the bond between oxygen and hydrogen (hydroxide group) if a compound contains this bond then it is most likely to have a high melting and boiling point since hydrogen bond is one of the strongest bonds. Hydrogen bond is a dipole (polar) bond, however not every dipole (polar) bond is necessarily a hydrogen bond. dipole dipole bonds, are bonds that occur between two elements that become polar due to the difference in electronegativity. polarity occurs when one element attracts the shared electrons stronger than the other element so that the electrons become closer to its nucleus because that element would have a higher electronegativity and thus the element with higher electronegativity would have a negative polarity while the other element would have a positive polarity and since negative attracts positive then a dipole dipole bond occurs hope that helped Edited December 2, 2007 by Ghanem9 Reply Link to post Share on other sites More sharing options...
Ghanem9 Posted December 2, 2007 Report Share Posted December 2, 2007 and if anyone finds anything i wrote wrong, please post as it would be help for me too Reply Link to post Share on other sites More sharing options...
BIO-AQUA Posted December 2, 2007 Report Share Posted December 2, 2007 Well what Ghanem9 just said is correct, but there are some few additions. - Van der Waals forces of attraction are temporary and instantaneous forces of attraction that exist between non-polar covalent molecules. How? The unbonded pairs of electrones in the outer shells have kinetic energy and can move freely. At a certain instant and due to their random motion, the electrones assemble/accumulate on one side, making an instantaneous temporary polar molecule. This polar molecule will induce its neighboring molecule to become polar (the highly dense negative side will repel electrones of the other molecule), thus an instantaneous electrostatic force of attraction is formed. This is called the Van der Waals force of attraction. As the molar mass, size and surface area increase, the Van der Waals forces become stronger as the valence electrones become less attracted to the nucleus and molecules are more easily polarized. - Dipole-Dipole force of attraction is a permanent electrostatic force of attraction that exists between polar covalent molecules. It is much stronger than the Van der Waals force. - Hydrogen Bond is the strongest bond between those and is a special case of the dipole-dipole force; it exists between the MOST polar bonds (H-O), (H-N) and (H-F). Note (1): Don't confuse these with the covalent bond. The forces above are attraction forces between covalent molecules. The covalent bond is a bond that exists within the covalent molecule and is much stronger than the three above. Note (2): For a molecule to be soluble in polar water, it must be polar and able to form Hydrogen bonds with polar water molecules. Hope this has helped. Have a nice day. Reply Link to post Share on other sites More sharing options...
stylusdef Posted December 2, 2007 Author Report Share Posted December 2, 2007 Ghanem9 & BIO-AQUA: Thanks, guys. I really appreciate your help. Finally, I get it! Reply Link to post Share on other sites More sharing options...
Ghanem9 Posted December 2, 2007 Report Share Posted December 2, 2007 you are most welcome... and thank you Bio dude i get it better now Reply Link to post Share on other sites More sharing options...
Bandev Posted December 3, 2007 Report Share Posted December 3, 2007 Hydrogen bonding is FON Reply Link to post Share on other sites More sharing options...
ysl89 Posted January 5, 2008 Report Share Posted January 5, 2008 Try this site: www.ibchem.com It provides a good explanation as well as graphic demonstrations Reply Link to post Share on other sites More sharing options...
Lotte Posted January 18, 2008 Report Share Posted January 18, 2008 (edited) Try this site:www.ibchem.com It provides a good explanation as well as graphic demonstrations I found that the ib chem site is rather skimpy on it's details... I took my notes on chapter four based off that site [as well as a few others for back up!] that my notes were a little superficial, and just comparing the other few sites I used [for specific things, i.e. to look up Dipole-Dipole or Van der Waals] were in a lot more depth than ibchem! It is just my opinion though, but I just thought the ibchem site skimped out on a lot of detail. [Edit] : I thought this site was good for the animations, and to a lesser extent the explanations [they're slightly complex for me, but I'm a little slow with science/maths! ]. Edited January 18, 2008 by Lotte Reply Link to post Share on other sites More sharing options...
tvd7 Posted February 21, 2008 Report Share Posted February 21, 2008 Ok, so I don't have the best chemistry teacher in the world...Could someone briefly explain what a van der Waals bond/force is? We've written notes during class, and mine say that van der Waal forces appear when vibrating electrons circulate around the nucleus of an atom, because of attractions to another atom. We've also written that "van der Waal bonds hate water." Could someone briefly explain what a hydrogen/dipole bond is? First off I'd like to know if a hydrogen bond is the same as a dipole bond, 'cause I think our teacher said so. The notes we've written say that dipole bonds appear when molecules are attracted to eachother's opposite charges. We've also written that hydrogen bonds love water. So. Please help! I can give a shot at your question about hydrogen bonds: Hydrogen bonds are NOT the same as dipole bonds!!! A hydrogen bond is the strongest type of bond and occurs between hydrogen and highly electronegative atoms (I think N, O, F only). Covalent substances with hydrogen bonds have a very high melting point because extra force is needed to break them. Reply Link to post Share on other sites More sharing options...
BIO-AQUA Posted February 22, 2008 Report Share Posted February 22, 2008 Hydrogen bonds are NOT the same as dipole bonds!!! A hydrogen bond is the strongest type of bond and occurs between hydrogen and highly electronegative atoms (I think O, F, S only but don't trust me on that). Covalent substances with hydrogen bonds have a very high melting point because extra force is needed to break them. True, but instead of O, F and S.. It's N, O and F!! Reply Link to post Share on other sites More sharing options...
deissi Posted February 22, 2008 Report Share Posted February 22, 2008 I fixed tvd7's post so that it's correct now Reply Link to post Share on other sites More sharing options...
Ongfufu Posted March 12, 2008 Report Share Posted March 12, 2008 1.Hydrogen bond: unusually strong dipole-dipole attractions that among molecules in which hydrogen is bonded to a highly electronegative element.2.Dipole-dipole attraction: the attractive force resulting when polar molecules line up so that the positive and negative ends are close to each other.3.Van der Waals’ forces: the forces, existing among noble gas atoms and nonpolar molecules, that involve an accidental dipole that induces a momentary dipole in a neighbor.Intermolecular_Forces.doc Reply Link to post Share on other sites More sharing options...
Bandev Posted March 19, 2008 Report Share Posted March 19, 2008 True, but instead of O, F and S.. It's N, O and F!! Therefore hydrogen bonding is FON. Oh and I agree with BIO-AQUA and the person above me, in saying that hydrogen bonds are dipole-dipole bonds. Reply Link to post Share on other sites More sharing options...
BIO-AQUA Posted March 19, 2008 Report Share Posted March 19, 2008 Therefore hydrogen bonding is FON. Oh and I agree with BIO-AQUA and the person above me, in saying that hydrogen bonds are dipole-dipole bonds. I thought you meant FON as in full of nonsense!! That's a good way to remember the combination by the way! Reply Link to post Share on other sites More sharing options...
nour__rashed Posted March 23, 2008 Report Share Posted March 23, 2008 HEY! My chemistry teacher rockks! HE gives us packaged notes on everythinnng in class. He posts all notes on his website. www.naturalstudy.ca Let me know if this works for you! Reply Link to post Share on other sites More sharing options...
Ivan91 Posted March 23, 2008 Report Share Posted March 23, 2008 HEY! My chemistry teacher rockks! HE gives us packaged notes on everythinnng in class. He posts all notes on his website. www.naturalstudy.ca Let me know if this works for you! where exactly are the notes ?? Reply Link to post Share on other sites More sharing options...
Guest The X Posted April 3, 2008 Report Share Posted April 3, 2008 The notes are no longer on the page apparently, I get "File not found" error messages when trying to view them. You can navigate through his home page to find them Reply Link to post Share on other sites More sharing options...
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