What is the coordination number of sodium in $Na_2O$?

The number of hexagonal faces that are present in a truncated octahedron is

In a face-centered cubic lattice,a unit cell face is shared equally by how many unit cells?

What is the total number of atoms present in an $fcc$ unit cell?

$A$ compound contains $Ca, Ti$ and $O$ elements. If $Ca^{2+}$ ions are at the corners of the cube,$Ti$ ions are at the body center,and $O^{2-}$ ions are at the face centers,then the molecular formula of the compound and the oxidation state of $Ti$ are respectively ........

What is the coordination number of a sphere in a simple cubic lattice?