Question

Please answer quickly, I don't understand how to do this properly.

Potassium forms ions with a charge of +1 (Ka+). 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

(Use the number 1 even if it isn't strictly necessary)

Answer 1

Answer :  2 and 1 are the numbers in the place of X and Y in $K_XSe_Y$.

Explanation :

Crisscross method : It is a method of finding a chemical formula in which ionic bond is formed by combining of metal and non-metal.

The charge on Potassium ion is +1 and the charge on Selenide ion is -2.

The potassium ions combined with the selenide ions to form a Potassium selenide. Image is also show below.

According to the crisscross method,

The formula of Potassium selenide is $K_2Se_1$.

Therefore, 2 and 1 are the numbers in the place of X and Y in $K_XSe_Y$.