Step 1: Recall the ideal gas law.
For an ideal gas, $\frac{PV}{RT} = 1$.
Step 2: Analyze the data.
From $P = 1$ to $P = 3$, $\frac{PV}{RT} = 1$, indicating ideal behavior.
For $P = 4$ and $5$, $\frac{PV}{RT}$ deviates from 1, indicating non-ideal behavior.
Step 3: Conclusion.
The gas behaves ideally in the pressure range 1 to 3 bar.
Final Answer:
\[
\boxed{1\ \text{to}\ 3}
\]