Answer
The name of $KNO_2$ is : "Potassium nitrite"
Work Step by Step
1. Identify the positive ion, and name it.
$K^+$ is the positive ion.
So, the first name of the compound will be: "Potassium."
2. Identify the negative ion, and name it.
$N{O_2}^-$ is the negative ion.
As we can see in Table 2.2 (Page 58), this ion is called "Nitrite".
3. Putting those two names together:
$K^+ + NO{_2}^- = KNO_2$
Potassium + nitrite = Potassium nitrite.
