# Homework Help: Largest lattice energy

1. Nov 15, 2007

### fk378

1. The problem statement, all variables and given/known data

Which one of the following ionic compounds has the largest lattice energy?

NaCl
CaO
Li2O
CaCl2

2. Relevant equations
Ionic/Atomic size
The smaller the ionic size, the larger the lattice energy.
Size increases from right to left, increases top to bottom of periodic table

3. The attempt at a solution
I've tried to compare the like ionic compounds, such as NaCl with CaCl2 but I can't seem to figure out which is bigger--Na+ or Ca2+

Am I approaching this incorrectly?

2. Nov 15, 2007

### ace123

Well if your losing electrons then the atomic size would what?

3. Nov 15, 2007

### fk378

Loss of electrons means smaller atomic radius. But Na and Ca don't have the same number of protons so isn't there another way to have to look at it?

4. Nov 16, 2007

### ace123

Well the loss of electrons makes the radius smaller. You know Na is one of the bigger elements size wise right? And the size decreases as you go across the periodic table. The protons don't attract the valence electrons as much as the core electrons b/c of shielding. Do you get it now?

5. Nov 17, 2007

### Kushal

are you considering charges?

L.E. is directly proportional to product of charges on ions but inversely proportional to sum of ionic radii.

hope it helps

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