What determines if an ion is negative or positive?

the number of electrons in it's outermost energy level

Explanation:

if the number of electrons in its outermost energy level is less than 4 that's the ion reacts by losing electrons and is thus the ion is positively charged

is the number of electrons in the outermost energy level is more than 48 react by gaining electrons and thus it is negatively charged

Ions are atoms with extra electrons or missing electrons. When you are missing an electron or two, you have a positive charge. When you have an extra electron or two, you have a negative charge.

Explanation:

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