* Sulfate Ion (SO₄²⁻): The sulfate ion has a charge of -2.
* Finding the Element: We need an element that also forms an ion with a -2 charge.
The most common element that forms a -2 ion is oxygen (O²⁻).
Explanation:
* Oxygen has six valence electrons (electrons in its outermost shell).
* To achieve a stable octet (eight valence electrons), it gains two electrons, resulting in an ion with a -2 charge.
Important Note: While oxygen is the most common element to form a -2 ion, other elements can also form ions with the same charge under specific conditions.
