Why is potassium oxide K2O instead of KO

For my chemistry homework we were provided with a table of ions and a periodic table. On the periodic table oxygen is in group 16 so its ion would have a charge of -2. It says that on the table of ions aswell, but there is also another oxygen ion that has a charge of -1. Wouldn't it be easier for the potassium ion (charge +1) to react with the oxygen ion with a charge of -1, or is it a typo or something?

Would appreciate a full explanation please.

I believe that the only case where O has an oxidation number of 1- is in peroxides.
Potassium Oxide is K2O because the oxygen wants to achieve 8 valence electrons. A neutral oxygen atom has 6, and it gains one from each K atom to form K2O.

K is 1+ and O is 2-
law of electroneutrality

the + must equal the -
http://www.kentchemistry.com/links/namin…

FYI the -1 is not a charge but an oxidation number.
http://www.kentchemistry.com/links/Redox…