3well i have found dat Li has lesser ionic radii than that of calcium in wikipedia.sry for confusions.
What is the order of lattice energy evolved during the formation of the following ionic compounds from their respective ion pair in gaseous state?
MgO, CaF2, LiF
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1ya,that might be a reason as the size differing by one shell.i actually didn't link these two.just applied the born-lande's concept.k.lets see.
106he said to consider charge density... then Li+ would have greater charge density than Ca2+
1From the Born-Landé equation it can be seen that the lattice energy of a compound is dependent on a number of factors :
i) as the charges on the ions increase the lattice energy increases (becomes more negative),
ii) when ions are closer together the lattice energy increases (becomes more negative)
obviously , LiF has less lattice energy than oder two wid respect to 1st point.
now, Ca+2 is having a larger ionic radii than Mg+2 , thus wid respect to 2nd point , MgO > CaF2.
thus, the order is what asish hs given.
106this was BT question and they have given the answer as MgO > CaF2 > LiF
for the reason they have just given the lattice energy values :(
1@msp is this written in jd lee that Ca2+ have smaller ionic radii than that of Li+.
3http://en.wikipedia.org/wiki/Born-Land%C3%A9_equation
i have read this in jd lee.but for reference u can see the above link.