Answer : The elements not balanced in this equation are, nitrogen (N), potassium (K) and oxygen (O).
Explanation :
Balanced chemical reaction : It is defined as the number of atoms of individual elements present on reactant side must be equal to the product side.
The given unbalanced chemical reaction is,

This chemical reaction is an unbalanced reaction because in this reaction, the number of atoms of nitrogen, potassium and oxygen are not balanced while all the atoms are balanced.
In order to balanced the chemical reaction, the coefficient 2 is put before the
.
Thus, the balanced chemical reaction will be,

Hence, elements not balanced in this equation are, nitrogen (N), potassium (K) and oxygen (O).