Final answer:
The assertion that sulfide, selenide, telluride, and polonide are always 2⁻ in binary salts is false, as the charges on cations vary to neutralize the compound, not strictly adhering to a 2⁻ charge.
Step-by-step explanation:
The statement that sulfide, selenide, telluride, and polonide are always 2⁻ in binary salts is false. While these anions typically carry a 2- charge, the corresponding cations can have different positive charges to balance the compound and make it neutral. For example, in iron(III) sulfide (Fe₂S₃), iron has a 3⁺ charge; in copper(II) selenide (CuSe), copper has a 2⁺ charge. It is essential to balance the charges to ensure the neutrality of the compound.
To create neutral compounds, the total number of positive charges must equal the total number of negative charges. Consider the gallium(III) nitride (GaN), where gallium is Ga³⁺ and nitride is N³⁻. Here, both ions have charges that are different from 2⁻, but the charges are balanced to form a neutral compound.