The molecular geometry of CN (cyanide ion) is linear. This is because CN consists of a carbon atom triple-bonded to a nitrogen atom, with a lone pair of electrons on the nitrogen. The triple bond between carbon and nitrogen results in a linear arrangement of the atoms, as the bond angle is 180 degrees.
In the cyanide ion, the carbon atom is sp hybridized, meaning it has two sp hybrid orbitals that form the sigma bonds with the nitrogen atom. The remaining two p orbitals on the carbon atom form pi bonds with the nitrogen atom, resulting in the triple bond. The linear geometry is a consequence of the sp hybridization and the repulsion between the electron pairs, which minimizes the repulsion by placing them as far apart as possible.