What is the crystal structure of $Na_2O$?

In solid $CsCl$,each $Cl^{-}$ ion is closely packed with how many $Cs^{+}$ ions?

Potassium crystallizes with a

The radius of $Na^{+}$ is $95 \, pm$ and the radius of $Cl^{-}$ ion is $181 \, pm$. What is the coordination number of $Na^{+}$?

Coordination numbers of $Zn^{2+}$ and $S^{2-}$ in the crystal structure of wurtzite are

In a compound,$W$ atoms are at the corners of the unit cell,$O$ atoms are at the edges of the unit cell,and $Na$ atoms are at the body center. The molecular formula of the compound is: