The empirical formula is NO₂.
Assume that you have 100 g of the compound.
Then you have 63.65g N and 36.35 g O.
Now, we must convert these masses to moles and find their ratios.
From here on, I like to summarize the calculations in a table.
Element Mass/g Moles Ratio Integers
N 63.65 4.543 1 1
O 36.35 2.2719 2.000 2
The empirical formula is NO₂.
