To find the empirical formula of compound X39Y13, we need to determine the simplest whole number ratio of the elements present in the compound.

Step 1: Find the greatest common factor (GCF) of the subscripts.

The GCF of 39 and 13 is 13.

Step 2: Divide each subscript by the GCF.

X39/13 = X3

Y13/13 = Y1

Step 3: Write the empirical formula using the simplified subscripts.

The empirical formula for compound X39Y13 is X3Y1.