<p>Given 3 substances, KI, NaBr, and Al2O3, how can I determine which has the greatest lattice energy and the least lattice energy?</p>
<p>I suppose I could look this up in my book. But then again…</p>
<p>Thanks in advance, nahrafsfa!!</p>
<p>which substance has the greatest electral negativity? (furthest apart on the table)</p>
<p>This is a hard one…you shoulda asked me last semester :-P…but i’ll definately check up on itwhen i get back to Tech (i’m at home right now)…but i’m guessing Al203 would have the greatest electronegativity and least lattice energy since Al and O are on the further extremes of the table. KI and NaBr would be neutral compounds…NOW for those 2…K is more reactive than Na so it’d more easily form a bond…but Br is a better reducing agent than I…so that makes things difficult…but just from guessing i’d choose KI to have a higher lattice energy since it’s ions are more reactive than Na.</p>
<p>don’t take my word for it quite yet!..i’ll definately get back to you monday around 12:30ish though!
actually…you know what…lemme refresh my memory with the net really quick</p>
<p>ok i was TOTALLY WRONG…the lattice energies for ionic compunds with larger charges would be larger. SOOO since Al has a 3+ charge and O has a 2- charge…Al2O3 would have the HIGHEST lattice energy. As you go UP the table lattice enrgy increases so Na Br would be second in line…and then KI would be last since it’s at the lower extremes of the table.</p>
<p>yes lattice enrgy decreases for either side of the periodic table (for both anions and cations) as you go DOWN the table. so the lower both ions are on the table, the lower the lattice energy…but moving down the cation side of the table (Na, K, blah blah) would have a more dramatic affect on the lattice energy of the compounds</p>
<p>and i’m still guessing Al2O3 will be more electronegative just because of the O…since Oxygen is the second most electronegative element, it’d pull Al ions further towards itself. KI and NaBr are electronegatively neutral i’m pretty sure…the further apart you are on the table, the more attraction you have towards eachother…the closer you are on the table…the more one ion pulls the atoms of the other ions towards itself, hence polarizing it to a higher extent, hence making it more electronegative</p>
<p>and O is more electronegative than Al is positive…so it’d increase the electornegativity of the compound as a whole…hope i helped!!!..sorry for my HORRIBLE mistake in the begining!</p>
<p>nahrafsfa, I think you are correct. Al2O3 greatest LE, KI least.</p>
<p>So basically the only way to find the answer is to look at the periodic table?</p>
<p>I was thinking we had to calculate something…</p>
<p>OK, so b/c Al2O3 has the higher charge (Al 3+ and O 2-) it has the greater LE. But KI and NaBr are both + -. How could I tell which has the least?</p>
<p>From what I’ve just read, LE depends on 2 things: ion charge, and atomic size. The greater the ion charge and the smaller the atomic size, the higher the LE; a vice versa.</p>
<p>So, for instance, given NaF, SrO, KF, SrCl2, and CsI.</p>
<p>higher LE = SrO (b/c of the higher ion charges)
least LE = CsI (b/c of their atomic sizes)</p>
<p>Thus, in order from least to greatest, CsI, KF, NaF, SrCl2, SrO. I think this is correct. If not, please let me know.</p>
<p>you are correct…the smaller the atomic size, and higher the charge, the higher the lattice energy. but the number one determinant is ionic charge…if you have elements with a 3+ and 3- charge binding together…they’ll have a higher lattie energy than elements with 1+ and 1- charges binding, or a 2+ and 3- charge binding. The larger the compound, lower the lattice energy</p>
<p>say you have NaBr and KBr…since K is lower on the periodic table KBr will have a lower lattice energy. now say you have NaBr and NaI…since I is lower on the periodic table NaBr would have the higher lattice energy. atomic size and ionic charge you’re gettin it!!!</p>
<p>why dont 'u just read the damn book</p>
<p>chem books aren’t fun to read through…and i dunno, but for me, it’s easier to understand when some1 explains it in plain language rather than text book language.</p>
<p>
</p>
<p>Yeah, okay. That’s kinda what was throwing me. But I’ve done a few dozen more off the internet and that seems to be the case with all of them.</p>
<p>Thanks again, Nahrafsfa!</p>
<p>no prob…if you have any more chem questions just post again!</p>