Question

If the ionic radii of $K^{+}$ and $F^{-}$ are about $1.34\mathring{A}$ each, then the expected values of atomic radii of $K$ and $F$ should be respectively:

• A. $1.34$ and $1.34\mathring{A}$
• B. $2.31$ and $0.64\mathring{A}$
• C. $0.64$ and $2.31\mathring{A}$
• D. $2.31$ and $1.34\mathring{A}$

Answer 1

The correct option is B $2.31$ and $0.64\mathring{A}$

If the ionic radii of $K^{+}$ and $F^{-}$ are about $1.34\mathring{A}$ each, then the expected values of atomic radii of $K$ and $F$ should be $2.31$ and $0.64\mathring{A}$ respectively.

Cations are always shorter than their parent atom, anions are always larger.

Thus radii of $K^{+}$ will be more than $1.34$ and that of $F^{-}$ will be less than $1.34$.

Hence, option $B$ is correct.