Explanation

The atomic mass of sodium is 23 g/mol.  

- This means 1 mole (6.022 × 10²³ atoms) of sodium weighs 23 grams.  

- So, the mass of one atom of sodium is:

= 23 g / Nₐ  

= 23 / (6.022 × 10²³) grams

So the correct option is: 23 / Nₐ g.