Question

Potassium forms ions with a charge of +1 (K+). Iodine forms ions with a charge of -1. Selenium forms ions with a charge of -2 (Se2-). Imagine that Potassium ions and Selenide ions combine to form Potassium Selenide. What numbers would be in the place of X and Y in: KXSeY?

Answer 1

It is given that the charge on potassium is +1 i.e. Potassium is a cation, K⁺

The charge on selenium is given as -2, i.e. selenium is an anion, Se²⁻

The two ions are shown to combine to form a molecule: KXSeY where X and Y correspond to the proportions in which the two atoms combine.

Since the molecule is neutral, the positive and negative charges need to be balanced. This is possible only if 2 units of K⁺ combines with 1 unit of Se²⁻.

Therefore, the formula would be K₂Se

X = 2 and Y = 1