Question

According to the VSEPR theory, a molecule with the molecular formula of `A_2` has what shape?

Answer 1

A molecule of this description must have a linear molecular geometry.

Explanation:

This is not actually due to valence shell electron pair repulsion (VSEPR), or "vesper", theory: in this molecule there would be only one region of electron density between the two atoms; notice the unusual turn of phrase since the covalent bond in this region could be a single bond (as in `"H"_2`), a double bond (as in `"O"_2`), or even a triple bond (as in `"N"_2`).

Imagine a straight line in a shape: as much as you alter the shape itself by changing angles, that original line itself will not be affected. In much the same way, that one region will not be affected by any number of lone pairs on the different atoms.

This of course not only applies to molecules with a molecular formula of `"A"_2` but also those of `"AB"`, such as the cyanide ion (`"CN"^-`).