Is an ionic bond stronger than a comparable covalent bond? If not, then why do ionic compounds typically have higher melting points than covalent compounds?
Nope, ionic bonds are generally weak (and intramolecular) bonds. The electrons are poorly shared (in fact, we say they are mostly transferred instead of shared), which is the opposite of what an ideal chemical bond is supposed to be (even electron sharing).
The less covalent a bond is, the weaker the bond is, for the same point of comparison.
Here’s an example.
Compare that to
#”Cl”_2(g) stackrel(“H”_2″O”(l))(->) 2″Cl”(g)#
So, the covalent bond in one molecule of
PHASE CHANGES (INTERMOLECULAR)
Melting point trends are not about bonds. They are about intermolecular forces, i.e. the interactions between compounds, NOT within compounds.
When you melt something, you try to separate the solid compounds themselves from each other (not into ions), increasing their motion until they move more freely than before, and become a liquid.
This involves breaking intermolecular interactions, such as dipole-dipole, hydrogen-“bonding” interactions, or ion-pairing interactions.
For instance, if you try to melt
On the other hand, if you try to dissociate it in water instead of melting it, it exists as
Since ion-pairing interactions are the strongest intermolecular force, it is hardest to melt ionic compounds, and thus, they have high melting points relative to, say, water, which has hydrogen-“bonding” as its strongest intermolecular force, and thus a low melting point.
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