Hey, just apply Coulomb's law, to calculate the electrostatic force of attraction,

 

where one charge = +1.602 x 10^-19 C & other charge = -1.602 x 10^-19 C , the distance is already mentioned and assume the medium between the two ions to be vaccum. The direction of the force is from positive sodium ion to the negative chloride ion. 

 

I hope I'm correct !!

 

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