What is the chemical formula for an ionic compound of potassium and oxygen?

Jan 24, 2017

Potassium oxyde, ${K}_{2} O$.

Explanation:

The last level of the electronic structure of oxygen is $2 {s}^{2} 2 {p}^{4}$. That means that there are two electrons in the $2 s$ orbital, two other electrons (paired) in one of the $2 p$ orbitals and the remaining two (unpaired) electrons placed one in each of the remaining $2 p$ orbitals.

This means that oxygen has two semi-occupied orbitals and, following the octet rule, will try to capture two more electrons to complete its structure and acquire that of a noble gas. That is, when it acts to form ionic bonds, oxygen acquires structure $2 {s}^{2} 2 {p}^{6}$ in its last level, forming the ion oxygen (2-): ${O}^{2 -}$.

On the other hand, potassium is an alkali metal whose last level occupied is $4 {s}^{1}$. That means that it will have a lot of tendency to lose that solitary electron and thus to form ionic compounds in which it takes the form of cation ${K}^{+}$.

Therefore, the binding of oxygen and potassium will give rise to an oxide of ionic character and ${K}_{2} O$ stoichiometric formula.