The formula "Nai" is incorrect and does not represent a known chemical compound.

Here's why:

* Sodium (Na) is a metal that forms a +1 cation (Na+).

* Iodine (I) is a non-metal that forms a -1 anion (I-).

To form a neutral compound, the charges must balance. Therefore, the correct formula for the compound formed between sodium and iodine is NaI (sodium iodide).