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Topic: Strength of an ionic bond  (Read 42800 times)

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Offline confusedstud

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Strength of an ionic bond
« on: September 04, 2012, 03:04:48 AM »
What affects the strength of the ionic bonds? Is it just the electrostatic forces of attraction between the ions or it is the number of ions? For example, when comparing Al2O3 and Na2O,the aluminium oxide has a higher melting point. So do we say that in Al2O3, aluminium ion has a charge of 3+ and the oxygen has a charge of 2- while in Na2O, the sodium only has a 1+ charge. Hence the forces of attraction between the Al and O is stronger than compared to Na and O.

Or, do we say that there are more oppositely charged ions in Al2O3 than in Na2O which causes the Al2O3 to have a higher melting point?

I'm guessing that we compare them by their electro negativity as in the lattice, the ionic bonds are between the two ions and it's only because of their charges which causes them to have a different ratio of ions but eventually it only the interaction between the two ions affects the ionic bond's strength?

Thanks! :-)

Offline Vidya

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Re: Strength of an ionic bond
« Reply #1 on: September 04, 2012, 03:14:52 AM »
In ionic compounds we do not have a chemical bond.It is merely attraction among the ions which results in the formation of ionic compounds.The strength of this electrostatic attraction is dependent on two factors:1) charges on the ions (more is the charge more is the attraction)
2) distance of separation between the ions (more is the separation less is the attraction) or we can say sizes of the ions -smaller is the size more stronger is the attraction.For example NaCl and NaBr.
Br > Cl hence NaCl has stronger attraction and stronger lattice then NaBr
in case of Al2O3 and Na2O
you compare the charges and then the sizes of the ions.Al3+ < Na+
so Al2O3 has higher charge and smaller size which results  in more stronger lattice then Na2O

Offline confusedstud

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Re: Strength of an ionic bond
« Reply #2 on: September 04, 2012, 03:31:04 AM »
Oh so only size and charge affects it. The number doesn't affect it right? Like in the aluminium oxide and sodium oxide, the number of aluminium and oxygen is larger but it doesn't have any effect on the ionic strength?

For example XY and X2Y3 where X and Y has the same charges in both cases (I know that's impossible but for example's sake haha). So the bonds here will be equally strong?

Thanks Vidya! :)

Offline Vidya

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Re: Strength of an ionic bond
« Reply #3 on: September 04, 2012, 04:06:00 AM »
I think numbers can  also be related with the charges.More is the charge ,more is the number of atoms if one of the atom is taken as fixed like XY and ZY2.In this case Z has more charge than X.

Offline Rutherford

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Re: Strength of an ionic bond
« Reply #4 on: September 04, 2012, 07:19:47 AM »
Ionic bond strength can be represented by Coulomb's law which determines the electrostatic force between two charged bodies (ions in this case):
F=k*q1q2/r2
q1-charge of one ion
q2-charge of the second ion
r-distance between them
k-the environment constant

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