Question

Which of the following ionic compounds has the highest melting point?

Help: Lattice energy
Select one:
a. Cs2O
b. K2O
c. BeO
d. SrO
e. LiF
f. CsI

Answer 1

Lattice energy generally decreases as we go down the periodic table and with charge. So mark off all of the group I oxides since they have +1 charge and that leaves just two from which to choose; i.e., SrO and BeO. BeO is more covalent bond whereas SrO is ionic. I think I would choose BeO as the higher melting point of the two; however, if you look them up on the web the mp of BeO is listed as 2507 C while that of SrO is 2531 C. Close but SrO is higher.

Answer 2

Which of the following ionic lattices would have the highest melting point?
A. Potassium oxide
B. Beryllium oxide
C. Boron nitride
D. Lithium chloride