Here's how to calculate the percent concentration of chlorine in sodium chloride (NaCl):

1. Determine the molar masses:

* Sodium (Na): 22.99 g/mol

* Chlorine (Cl): 35.45 g/mol

2. Calculate the molar mass of NaCl:

* NaCl = 22.99 g/mol + 35.45 g/mol = 58.44 g/mol

3. Calculate the mass percentage of chlorine:

* (Mass of chlorine / Molar mass of NaCl) * 100%

* (35.45 g/mol / 58.44 g/mol) * 100% = 60.66%

Therefore, the percent concentration of chlorine in sodium chloride is approximately 60.66%.