Covalent vs Ionic Bonds, Which is Stronger?

okay, first to start out, a precise answer would be that covalent bonds is stronger. But like all knowledge aquisition, one should be looking for the most accurate answer, and not the most precise answer.

also, one must understand that in comparing items, you cannot use specific examples, simply because you're assuming that there's a trend in the subjects used, and this assumption is VERY likely to fail, especially in the atomic world. basically, this is also the reason why you dont use specific terms to determine if a sequence is an A.P or a G.P, you need to use induction methods to prove that your results is consistent with all the terms.

there's a proposal of theory that covalent bonds is stronger than ionic bonds. Why? Solely because the melting/boiling points of diamond is the highest. Does this make any sense? In my opinion(as with many other scientists), it don't, at all. Why? simply because like all proofs, how sure are you that this trend is held by all covalent and ionic substances? Hence, using diamond as the hardest/most thermally stable substance is not a valid argument in trying to show that a covalent bond is stronger than an ionic bond.

to push my argument that you cannot compare the bonds, here's a few reasons.

Firstly, the theory of a covalent of ionic compound is dependent on the difference in electronegativity between compounds. In reality, NO substance is purely covalent or purely ionic. It's a theory, just like your perfect competition is economics theory. Put simply, the covalent or ionic character of a bond is a continuum, but not discrete. Hence, when you compare a trend of strength of covalent or ionic bond, how are you, then, able to take into account the measure of ionic characteristic in a covalent bond, or the covalent characteristic in an ionic bond?

Secondly, the energy required depends on HOW you break the bond.(Common Examples are: homolytic cleavage, or heterolytic cleavage.) Basically, if you want to separate two non-polar atoms(C and H), you have to simply break the bonds in between. However, if you want to have a net transfer of electrons(heterolytic cleavage), you will need more energy to ionise the electron from one atom, and for the other atom to accept the electron. So, the energy required to break a covalent or ionic bond depends on the type of cleavage of the bonds.

Thirdly, it depends on the phase of your substance when you break the bonds. Ionic bonds tend to require a lower energy for bond-breaking in polar substances such as water, due to the formation of ion-dipole bonds between the ionic compound and water molecules, and this formation of bonds will weaken the ionic bonds between the ionic compound, hence a lower energy is required to break the bonds. Covalent compounds, even when dissolved in a solvent, wouldn't be affected any more than that of ionic compounds. Simply because their bonding is not affected to the same extent of that of ionic bonds.

Fourthly, the energy required to break either covalent or ionic bonds is also dependent on the nature of the substituents of the atoms involved. For example, electron donating substituents will strengthen the bonds in between by providing more electrons, which fundamentally forms the bond.

Fifthly, to even conclude the trend that bond strength is dependent on the difference of electronegativity between the atoms is not valid. Here's an example of anomaly in the trend.

Li-F:1017kJ/mol(Difference in Electronegativity:3.0)
Li-Cl:828kJ/mol(Difference in Electronegativity:2.8)
Li-Br:787kJ/mol(Difference in Electronegativity:1.8)
The examples seem to follow a trend where the energy required to break the bond is dependent on the difference in electronegativity. However, as this example moves on, here's an anomaly.

Mg-O:3890kJ/mol(Difference in Electronegativity:2.3)

Hence, even such a strong trend used to explain various chemistry concepts do not survive, when they are subjected to closer scrunity.

Sixthly, the comparison of melting/boiling point of a substance of compounds do not show how strong the covalent or ionic bond is. Simply because some covalent substance like N2 and O2 forms triple bonds and double bonds respectively, while F2 forms a single bond between atoms.
Which value, of covalent bonds, will you then use for comparison?

Seventhly, how do one determine whether a bond between atoms is covalent or ionic? Covalent bonds are usually defined as the bond between atoms of electronegativity difference of less than 1.5, while ionic bonds are usually defined as the bond between atoms of electronegativity difference of more than 2. But the question is, how accurate is this definition? Why, then, is the bond between Na and Br atoms considered ionic, when the electronegativity difference is only 1.9. Why, then, is the bond between H and F atoms considered covalent, when the electronegativity difference is 2.9? So, how are we able to compare two categories of items, when we cannot even distinguish the dividing line clearly?

Therefore, unless you are able to get a clear formula to determine the strength of a bond, regardless of the type of bonding, you will NOT be able to compare the strength of a covalent and an ionic bond.

Lastly, the only accurately way we are able to compare whether a covalent and ionic bond is stronger is to have a substance that can exist in both covalent and ionic states. However, unfortunately, such a substance do not exist. Hence, what grounds, then, do we have for comparison?

If you think a little deeper, there exist a fair share strong and weak covalent and ionic bonds. This means that if we are to the strength of covalent bonds with the strength of ionic bonds between various compounds, some covalent bond strength would be higher than that of ionic bond, but the reverse holds true. Therefore, this question do not really make any sense.

To digress a little, here's a bit of interesting information that i found on the web:
1:the strongest of the weak bonds(hydrogen bonding, pd-pd bonds, id-id bonds) can also be stronger than the weakest of the strong bonds(covalent or ionic bonds).

This is unlike what we learn in A levels chemistry, where we are told that if the boiling point of a molecule is low, it's held by weak forces of attraction, and vice versa. Apparently, now we know that when the boiling point is low, it can also be held by strong forces of attraction.

2:Ionic bonds are around 80 times weaker when dissolved in water.

Basically, in the A' level syllabus, we're learning that it forms ion dipole bonds with the water molecules, and breaks the ionic bond between the ions, hence energy required is not used to break the ionic bonds, but the ion dipole bonds which are about 80 times weaker.

Sources:

1. Newton source 1
2. Newton source 2
3. MadSci network
4. WikiAnswers(not very good, though)
   

Also, i got a question of whether this degree of information that I'm looking for even useful to the A' levels that I'm taking. Well, I believe that it really depends on the reason why you're acquiring knowledge. What i must say, is that if you acquiring knowledge for the sake of A' levels, you're really missing a BIG part of this hunt for knowledge.

So, maybe this is the time for you to think about the reason why you're studying. So that you can pass your major examinations to secure a well-paying job in the future? or maybe to not let the people who pinned hopes upon you down. or maybe, is it even that you yourself don't know why you are studying and acquiring knowledge.

Now, answer the question, why do you study?