Question

1.Rank the following three ionic compounds in order of increasing lattice energy: NaF, KCl, MgO. (Your answer should have highest lattice energy first, lowest last.) A) NaF > KCl > MgO B) NaF > MgO > KCl C) KCl > NaF > MgO D) KCl > MgO > NaF E) MgO > NaF > KCl F) MgO > KCl > MgO

2.In which ONE of the following compounds would the bonding be expected to
have the highest percentage of ionic character?
A) LiBr B) RbF C) MgBr2 D) NaCl E) KI

Answer 1

1) The lattic eenergy of ionic compounds is proportional toproduct of charges of ions and inversely proportional to the sum of radii.

Thus MgO which has +2 and -2 charges on the ions has the highest lattice energy and KCl which has the largest ions by size have least lattice eenrgy. NaF has more than KCl due to the smaller size of both Na+ and F-

thus the order of decreasing lattice energy is

MgO > NaF > KCl

OPTION E

2) The smaller the anion and the larger the cation the stronger is the ionic bond.

Thus RbF among the given ones has the highest ionic character.