You get 2 sigma and 4 pi bonds per formula unit of calcium cyanide.
First, it must be noted that calcium cyanide,
Before taking a look at the Lewis structure of the cyanide ion, remember that you have
- single bond
#->#one sigma bond and no pi bonds;
- double bond
#->#one sigma bond and one pi bond;
- triple bond
#->#one sigma bond and two pi bonds.
So, the Lewis structure of the cyanide ion looks like this
Notice that you have a triple bond between the carbon atom and the nitrogen atom. This means that you get one sigma bond and two pi bonds per cyanide ion.
Since the formula unit of calcium cyanide contains 2 cyanide ions, you will end up with a total of
- two sigma bonds;
- four pi bonds.