Question

20. Which of the following has the highest Ionic character? LiOH, NaOH, KOH, ROOH, CsOH. ​

Answer 1

I think the answer is KOH

Answer 2

LiOH has the highest ionic character.

Li, Na, K, Rb, Cs all belong to group 1 of the modern periodic table.

From the periodic properties of the periodic table, we know that size of elements usually increases down the group unless there is an exception.

In group 1 there is no exception, so the size of elements increases from Li to Cs

Similarly, size increases from Li⁺ to Cs⁺

We know that the ionic character is directly proportional to the lattice energy

Lattice energy is proportional to $\frac{q1 q2}{r^{2} }$ where q1 is the charge of cation, q2 is the charge of anion and r is the radius of the ionic compound.

Here, the charge of all the cations is the same, i.e., +1, and the charge of anions is -1.

So, we have to compare the radius of the compounds

The radius of the cations increases from Li⁺ to Cs⁺

The radius of Li⁺ is the least so its lattice energy will be the maximum

Therefore, the ionic character of LiOH will be maximum.