Look at the sodium choride structure in the figure and use it to calculate `(r^(+))/(r^(-))`

Explanation

Along an edge,
`2r^(+)+2r^(-)=a`
`r^(+)=((a)/(2)-r^(-))`
Along a diagonal, `4r^(-)=asqrt2`
`therefore" "a=(4r^(-))/(sqrt2)=2sqrt2r^(-)`
`therefore" "r^(+)=(2sqrt2r^(-))/(2)-r^(-)`
`r^(+)=r^(-)[sqrt2-1]`
`(r^(+))/(r^(-))=sqrt2-1=1.414-1=0.414.`