the answer to your question is
volume
Galvanizing protects from rust in a number of ways: It forms a barrier that prevents corrosive substances from reaching the underlying steel or iron. The zinc serves as a sacrificial anode so that even if the coating is scratched, the exposed steel will still be protected by the remaining zinc.
1.3 x 10^21 atoms Na is 4.63230769231 mol Na
4.63230769231 mol Na * 23g/mol Na = 106.543076923g
Since f=ma assuming you knew the mass of the marble and the total amount of force acting on it than you would divide the amount of force by the mass.
