Question

Which of the following has the largest % of sodium, 20g of sodium fluoride, 20g of sodium chloride, or 20g of sodium bromide?

Answer 1

the one whose molar mass is smaller than sodium. 

Fluorine is 19 g
Chlorine= 35.5 g
Bromine= 80 g

so in sodium fluoride, the percent of sodium is the largest.