Figure 2: FCC Octahedral Sites represented by unfilled circles and a red filled circle. 13 equivalent locations in total. 2) What would be the atomic percentage of carbon in each type of iron if all the interstitial sites were filled? The basis for atomic percentage (at\%) is the number of moles of an element in relation to the total moles of the elements in an alloy and may be computed as follows: at%metal1=atomsmet+atomssmetatomssmetal1100