The Linear Shape (AX2)
The linear shape is a type of shape which a molecule takes form of when the bonding pairs are at opposite ends of a straight line. The angle of the bond would be exactly 180 degrees. The linear shape is also a symmetrical molecule therefore making it non-polar. The lone pairs it has depends on the type of molecule it is. Some examples of linear shape molecules would include:
Carbon Dioxide
Beryllium Hydride
In a linear shape, the two atoms don't have to be the same. There can be up to three different atoms which can form a linear shape. For example:
Hydrogen Cyanide
What contributes to this shape?
The only thing that contributes to this shape are the two bonds which the central atom is attached to. There are no lone pairs of electrons which would cause a repulsion with the surrounding atoms and thus providing a different bond angle and shape. Since there are only two bonds attached to it and no lone pairs, the bond angles tend to be 180 degrees due to their inability to bend.