A completely filled band is called:

Explanation

In certain specific materials like insulators and semiconductors, the valence band is typically not fully filled at normal ambient conditions. It contains electrons occupying various energy states, but there are still available energy levels within the valence band for electrons to move around and participate in bonding. However, in some cases, particularly with certain elements or compounds, the valence band can be nearly full or completely filled. This configuration usually contributes to their insulating properties because there's limited availability of energy states for electrons to move and conduct electricity.