Sodium, Atomic mass: 22.989769 g
You can see in a periodic table
        
             
        
        
        
Moles of NaN3 at STP  = volume of gas / 22.4 = 11.5/22.4 = 0.5mole. Massof NaN3 = moles of NaN3 x molecular weight = 0.5 x 65 = 32.5 grams.
        
                    
             
        
        
        
For Nitrogen Atom: 
 Atomic Number - 7
 Protons - 7
 Neutrons - 8
 Electrons - 7
 Cation/Anion - Anion
For Nitrogen Ion: 
 Atomic Number - 7
 Protons - 7
 Neutrons - 8
 Electrons - 10
 Atomic Symbol - N3-