Ionic Bonding (Section)The ionic substances NaF, CaO, and

Chapter , Problem 23E

(choose chapter or problem)

Problem 23E

Ionic Bonding (Section)

The ionic substances NaF, CaO, and ScN are isoelectronic (they have the same number of electrons). Examine the lattice energies for these substances in Table Make a graph of lattice energy on the vertical axis versus the charge on the cation on the horizontal axis

Table Lattice Energies for Some Ionic Compounds

Compound	Lattice Energy (kJ/mol)	Compound	Lattice Energy (kJ/mol)
LiF	1030	MgCl2	2326
LiCl	834	SrCl2	2127
LiI	730
NaF	910	MgO	3795
NaCl	788	CaO	3414
NaBr	732	SrO	3217
NaI	682
KF	808	ScN	7547
KCl	701
KBr	671
CsCl	657
CsI	600

(a) What is the slope of the line? (b) Make a graph of lattice energy on the vertical axis versus the square of the cation charge on the horizontal axis. What is the slope of this line? (c) Compare how well the data points fall on a line for the graphs in (a) and (b). Which trend is more linear, lattice energy versus cation charge or lattice energy versus cation charge squared? (d) Predict the lattice energy for the compound TiC, if we consider the carbon to have a 4-charge.