Question

The pair of elements which on combination are most likely to form an ionic compound is:

• A. $Na$ and $Ca$
• B. $K$ and $O$
• C. $O$ and $Cl$
• D. $Al$ and $I$

Answer 1

The correct option is B $K$ and $O$

Ionic compounds are formed by electrostatic attraction between a cation(metal ion) and anion (non-metal ion) of similar size. If the size difference is such that cation is small and anion is very large, they form bond with more covalent character.

A: Both $Na$ and $C$ are cations-No ionic bond can be formed

B: $K$ is a metal and $O$ is non-metal and exist as $K^{+}$ and $O^{2-}$. Therefore have Ionic bond

C:$O$ and $Cl$ both are anionic-no ionic bond

D:$Al$ is cation and $I$ is anion. They can form ionic bond but due to large size difference between $A{l}^{3+}$ and $I^{-}$, they posses more covalent character.

Hence option B is correct.