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Molecules are ionic if there is a significant difference in electronegativity between two atoms, ie. atoms from different ends of the periodic table. They are covalent if the atoms have similar electronegativities.
Hydrogen bonding is something completely different. This is to do with intermolecular forces. Hydrogen bonding only occurs between molecules that have either oxygen, nitrogen, florine and of course hydrogen atoms.
Hydrogen bonding is something completely different. This is to do with intermolecular forces. Hydrogen bonding only occurs between molecules that have either oxygen, nitrogen, florine and of course hydrogen atoms.
Thank you to JayEm and ImperceptibleNinja for helping me. The thing that I actually don't understand is how do we know a molecule has metallic bond, ionic bond, covalent bond, hydrogen bond. When I read the textbook, it states that this molecule has this bond or that bond..how do we know that? And then there are those permanent dipole force, instantaneous induced dipole force..how do we know which force a molecule has? Can you please give me some examples of each bond because I really don't understand about it.
Yes about the repulsion theory, I will write what my textbook wrote:
Carbon dioxide has two carbon-oxygen double bonds. Multiple bonds are best considered in the same way as single electron pairs. If the two double bond pairs repel each other as far as possible, the molecule is predicted to be linear.
I don't understand what it said by how the bond pairs repel and how they get the bond angle. Like why it's predicted to be linear for carbon dioxide and then it's 109.5 degree in CH4..then it's 107 degree in NH3. I don't know how they get this value...I think the thing I want to know this how they repel till they get those values of the bond angle.
Often we are given a question which asks for the shape and bond angle..how do we predict them? For example, what are the shape and bond angles of PCL5 molecule and PCL4+ ion?
Sorry for my ignorance..Thanks.
Yes about the repulsion theory, I will write what my textbook wrote:
Carbon dioxide has two carbon-oxygen double bonds. Multiple bonds are best considered in the same way as single electron pairs. If the two double bond pairs repel each other as far as possible, the molecule is predicted to be linear.
I don't understand what it said by how the bond pairs repel and how they get the bond angle. Like why it's predicted to be linear for carbon dioxide and then it's 109.5 degree in CH4..then it's 107 degree in NH3. I don't know how they get this value...I think the thing I want to know this how they repel till they get those values of the bond angle.
Often we are given a question which asks for the shape and bond angle..how do we predict them? For example, what are the shape and bond angles of PCL5 molecule and PCL4+ ion?
Sorry for my ignorance..Thanks.
There's no formula to calculate bond angles, it's something you just have to memorize. However, the good news is that you can memorize "template" molecules and their bond angles. Basically, memorize what bond angles and shape a molecule has if it has say x bonding pairs and y lone pairs, and then apply this to other molecules. If you want I have a table which sums this all up and if you essentially memorize that and a few examples, you can't go wrong.
Civ-217
The thing that I actually don't understand is how do we know a molecule has metallic bond, ionic bond, covalent bond, hydrogen bond. When I read the textbook, it states that this molecule has this bond or that bond..how do we know that? And then there are those permanent dipole force, instantaneous induced dipole force..how do we know which force a molecule has?
First of all you need to differentiate between INTERmolecular and INTRAmolecular bonding. INTRAmolecular bonding is between atoms of molecules and that's where you get ionic and covalent bonding. INTERmolecular bonding is between molecules of a compound/element and that's where you have hydrogen bonding and permanent dipole forces and instantaneous induced dipole forces.
Metallic bonding is only in metallic ELEMENTS. e.g. Al, Na, Mg all are metals and exist on their own. Ionic bonding is OFTEN between metals and non-metals e.g. NaCl, CaO etc. And about knowing what molecule has what bonding, I used to have that problem too and there's no straight hard and fast rule that will tell you. It just comes from reading alot and doing alot of examples and learning really, so keep reading and do lots of examples.
Intermolecular bonding is easier to predict. Hydrogen bonding forces only exist between H-O, H-F, and H-N atoms of molecules. e.g. in water H2O which is H-O-H you can have hydrogen bonding between the H atoms of one water molecule and the O atoms of another water molecule.
edit: sorry for the double post. does this forum have a multiquote thing?
Well, a simple guide for knowing if bonds are ionic or covalent (or metallic) -->
A metal bonded to a non metal is ionic
A non-metal bonded to a non-metal is covalent
A metal bonded to a metal is metallic.
As for instantaneous induced or permanent dipole bonds; you ONLY get these when the bonding is simple covalent (i.e. where molecules exists). You always get instantaneous/induced dipole bonds between molecules, which occur when two molecules (say X1 and X2) come close. The electrons in X1 "push" the outer electron in X2 to the opposite side of X2, so you then have a dipole on X2 (the side the electrons have been pushed to is negative, while the other side is electron deficient, so is positive. This dipole then causes a dipole on molecule X1 and so on in a sort of chain reaction. However, these dipoles only last for a second (hence the instantaneous).
If the molecule is symmetrical you don't get any permanent dipole bonds, but if its is unsymmetrical then you may. These form when one of the atoms in the molecule is a lot more electronegative, so "draws in" lots of electrons from that molecule to it, thus making the side it's on a little negatively charged, and the opposite side a little positively charged.
A metal bonded to a non metal is ionic
A non-metal bonded to a non-metal is covalent
A metal bonded to a metal is metallic.
As for instantaneous induced or permanent dipole bonds; you ONLY get these when the bonding is simple covalent (i.e. where molecules exists). You always get instantaneous/induced dipole bonds between molecules, which occur when two molecules (say X1 and X2) come close. The electrons in X1 "push" the outer electron in X2 to the opposite side of X2, so you then have a dipole on X2 (the side the electrons have been pushed to is negative, while the other side is electron deficient, so is positive. This dipole then causes a dipole on molecule X1 and so on in a sort of chain reaction. However, these dipoles only last for a second (hence the instantaneous).
If the molecule is symmetrical you don't get any permanent dipole bonds, but if its is unsymmetrical then you may. These form when one of the atoms in the molecule is a lot more electronegative, so "draws in" lots of electrons from that molecule to it, thus making the side it's on a little negatively charged, and the opposite side a little positively charged.
Thank you for all your helps. I understand it better now but I still have a few questions.
I get confused with "..between atoms of molecules" and "between molecules of a compound element". It's because I never really understand what atom and element are. Elements are like those Na, Ag right?..but what about atoms?
What is meant by "the molecule is symmetrical"?
I've few more questions:
3)Actually what does dipole mean? I see this word quite often but never get to know what it means.
4)My textbook says that the tetrachloromethane, CCl4 has four polar bonds. The four dipoles point towards the corners of the tetrahedral molecule, cancelling each other out, so it's non-polar. I don't understand what they mean by "cancelling each other out" and so the molecule is non-polar. Why is it so?
5)From my textbook, the bond angle of PCl5 molecule is 120degree and 90 degree. But what about the bond angle of PCl4+ ion? How to know the bond angle in this case?
Thank you very much.
Intelligentsia
INTRAmolecular bonding is between atoms of molecules and that's where you get ionic and covalent bonding. INTERmolecular bonding is between molecules of a compound/element and that's where you have hydrogen bonding and permanent dipole forces and instantaneous induced dipole forces.
I get confused with "..between atoms of molecules" and "between molecules of a compound element". It's because I never really understand what atom and element are. Elements are like those Na, Ag right?..but what about atoms?
Prometheus
If the molecule is symmetrical you don't get any permanent dipole bonds, but if its is unsymmetrical then you may. These form when one of the atoms in the molecule is a lot more electronegative, so "draws in" lots of electrons from that molecule to it, thus making the side it's on a little negatively charged, and the opposite side a little positively charged.
What is meant by "the molecule is symmetrical"?
I've few more questions:
3)Actually what does dipole mean? I see this word quite often but never get to know what it means.
4)My textbook says that the tetrachloromethane, CCl4 has four polar bonds. The four dipoles point towards the corners of the tetrahedral molecule, cancelling each other out, so it's non-polar. I don't understand what they mean by "cancelling each other out" and so the molecule is non-polar. Why is it so?
5)From my textbook, the bond angle of PCl5 molecule is 120degree and 90 degree. But what about the bond angle of PCl4+ ion? How to know the bond angle in this case?
Thank you very much.
Civ-217
I get confused with "..between atoms of molecules" and "between molecules of a compound element". It's because I never really understand what atom and element are. Elements are like those Na, Ag right?..but what about atoms?
Ok I'm going to start real basic, just so you've got your basics right... like gcse if that's ok. All matter is made up of elements. All elements are made up of atoms. Atoms combine with each other to form molecules of compounds. So once again, atoms of elements form molecules of compounds. To form molecules, atoms can combine covalently or ionically. e.g. water is a covalent compound. This is what I am referring to by "..between atoms of molecules". Maybe I should have said WITHIN atoms of molecules if that helps.
Now all of these molecules have forces between them which hold the molecules together. This is what is meant by "between molecules of a compound".
Thank you so much.
I will ask if I don't understand something about those again. I've some questions about Bronsted-Lowry definition of acid and base.
NH4+ (aq) + CO3²- (aq) -><- HCO3- (aq) + NH3(aq)
It is said in the textbook that ammonium donates a proton to the carbonate ion, and forms ammonia. Thus ammonia is an acid, and the ammonia is its conjugate base. The carbonate ion accept a proton, forming a hydrogencarbonate ion. Thus the carbonate ion is its conjugate acid.
I don't understand these whole bold sentences. I mean it says that ammonium donates a proton to the carbonate ion and forms ammonia...so does that mean NH4+ -> NH3 + H+ ? If it is like this, then I don't understand this equation, I mean how NH3 + H+ gives NH4+ ... the same goes for the carbonate ion.
Thanks.
I will ask if I don't understand something about those again. I've some questions about Bronsted-Lowry definition of acid and base.NH4+ (aq) + CO3²- (aq) -><- HCO3- (aq) + NH3(aq)
It is said in the textbook that ammonium donates a proton to the carbonate ion, and forms ammonia. Thus ammonia is an acid, and the ammonia is its conjugate base. The carbonate ion accept a proton, forming a hydrogencarbonate ion. Thus the carbonate ion is its conjugate acid.
I don't understand these whole bold sentences. I mean it says that ammonium donates a proton to the carbonate ion and forms ammonia...so does that mean NH4+ -> NH3 + H+ ? If it is like this, then I don't understand this equation, I mean how NH3 + H+ gives NH4+ ... the same goes for the carbonate ion.
Thanks.
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