What is the mass percent of sodium in nacl?

Mass percent of sodium is mass of sodium divided by total mass of NaCl then multiplied by 100%.  That means that percent mass equals (23g/58.45g)×100% which equals 39.3%.
Therefore the percent mass of sodium in NaCl is 39.3%
I hope this helps.  Let me know if anything is unclear.

500bc indiais the answer.