Firstly, I'm going to list the electronegavitivies of each element
Sodium: 0.93
Calcium: 1.00
Hydrogen: 2.2
Carbon: 2.55
Fluorine: 3.98
All that needs to happen now is to determine the difference, which is literally taking the smaller number away from the large number.
It is already apparent that sodium and fluorine have the biggest difference.
