Final answer:
In the perchlorate ion, the formal charge on chlorine (Cl) is 0. This is found by comparing the assigned electrons to the valence electrons and applying the formal charge calculation, which equals zero for a stable structure.
Step-by-step explanation:
The formal charge on Cl in the perchlorate ion is calculated by assigning electrons to the atom, comparing the assigned number to the valence electrons of the neutral atom, and applying formal charge formulas. For perchlorate, Cl is surrounded by oxygen atoms and carries no formal charge since all formal charges in the most stable structure should add up to zero as per Guideline 1. Specifically, each Cl atom has seven electrons assigned to it, equating to the number of valence electrons (7) in its neutral atomic state, leading us to a formal charge calculation of Cl: 7-7 = 0