Question

1) Which of the ions Mg²⁺, Sr²⁺, Ca²⁺, Be²⁺, Ba²⁺, or Ra²⁺ is the largest?

2) Lattice Energy

The following compounds all display the NaCl structure. (i.e. They are isomorphous.) For each pair, indicate which would have the lattice energy of greater magnitude. ​

a) CaS or CaSE

b) SrO or CaO

c) CaO or NaCl

d) NaI or LiI

e) MgO or CaS

*Consider how the relative energies of interaction of "point" charges would vary with respect to the expected interionic distances, according to Coulomb's Law. (Detailed calculations should NOT be required to make these comparisons -- but consider, for example, the relative effects of doubling the charges, as compared to increasing the interionic distances.)​*

Answer 1

1) Among the following, Ra⁺² is having greater radius because it is the extreme last element in the group and having greater atomic radius.

2) The lattice energy is more for ions which are having greater charge and smaller size. Thus -

a) CaS having greater lattice energy

b) CaO is having greater latice energy

c) CaO is having greater lattice energy (Ca⁺² is having smaller size)

d) LiI is having greater lattice energy (Li⁺ is having smaller size)

e) MgO is having greater lattice energy (Mg⁺² is having smaller size)