Question on molecules with linear shape

[hannaluong4E]

If a molecule has a linear shape does that guarantee the bond angle will be 180 degrees and non polar? An example would be XeF2 (AX2E3) which has a trigonal bipyramidal electron arrangement but a linear shape, with bond angle 180 degrees.

I just wanted to clarify because I always determined bond angles to be = slightly less than the bond angle of its e- arrangement. (And so I thought the bond angle in XeF2 was <90 degrees).

[Chem_Mod]

Linear molecules can certainly be polar. Polarity occurs because of differences between electronegativity on the atoms participating in the bond. For example, CN^- is linear and polar. Linearity does imply a 180 degree bond angle.

[Hannah Markovic 3C]

Bond angles are only less than the values we memorize only when there are electron pairs that make the molecule not symmetric. Although XeF2 has three electron pairs, they are in a symmetrical arrangement around Xe so the bond angle is still exactly 180 degrees. The values we memorize are for when there are no excess electron pairs in the molecule, so either if there are no electron pairs or if the electron pairs are arranged symmetrically then the values will be exactly what we memorize. Otherwise, we say they are slightly less.