Final answer:
Chloride ion (Cl-) is predominantly found outside the cell to balance the net positive charge resulting from metal ions like K⁺, Na⁺, and Ca²⁺.
Step-by-step explanation:
The negatively charged ion that is predominantly found outside the cell to balance the net positive charge resulting from metal ions like K+, Na+, and Ca2+ is chloride ion (Cl-). Chloride ions primarily neutralize the net positive charge by accumulating outside the cell, where they are repelled by negatively-charged proteins within the cytoplasm.