Final answer:
The bond angle for linear molecules is 180º, with carbon dioxide (CO2) and beryllium hydride (BeH2) being examples of such molecules.
Step-by-step explanation:
The bond angle in linear molecules is exactly 180º. This occurs because the molecule's central atom has only two electron groups, which orient as far apart from each other as possible to minimize repulsion, resulting in a linear geometry. Carbon dioxide (CO2) is a classic example of a linear molecule, where the oxygen atoms are bonded to the central carbon atom with double bonds, creating a structure written as O=C=O.
Another linear molecule is beryllium hydride (BeH2), which also has a bond angle of 180º, represented as H-Be-H. These structures illustrate that any two-atom molecule or any molecule with a central atom and two electron groups will indeed have a linear shape with bond angles of 180º.