To determine how the formula will be when combining two ionic species, we must look at the oxidation states of the ions. The Na ion has an oxidation state of +1 and the ClO4 ion has an oxidation state of -1.
The number of ions must be such that the total sum of the oxidation states is zero. If we have a Na+1 ion and a ClO4(-1) ion, the sum will be equal to zero. So there must be one ion of each species in the molecule.
[tex]Na^{+1}ClO_4^{-1}\rightarrow NaClO_4[/tex]
Therefore, the answer will be: NaCIO4
