Answer
$Na-Cl$ distance: $2.83$ angstroms
$K-F$ distance: $2.71$ angstroms
Work Step by Step
1) Find the ionic radii of the ions:
- Ionic radium of $Na^+$: $1.16$ angstroms
- Ionic radium of $Cl^-$: $1.67$ angstroms
- Ionic radium of $K^+$: $1.52$ angstroms
- Ionic radium of $F^-$: $1.19$ angstroms
2) To find $Na-Cl$ distance and $K-F$ distance, we sum the ionic radii of the ions together. In detail,
- $Na-Cl$ distance: $1.16+1.67=2.83$ angstroms
- $K-F$ distance: $1.52+1.19=2.71$ angstroms
