Linear molecular geometry

Idealised structure of a compound with linear geometry.
Structure of beryllium fluoride (BeF2), a compound with a linear geometry at the beryllium atom.

In chemistry, the linear molecular geometry describes the geometry around a central-atom bonded to two other atoms (or ligands) placed at a bond-angle of 180°. Linear=organic molecules, such as acetylene (HC≡CH), are often described by invoking sp orbital hybridization for their carbon-centers.

According to the VSEPR model, linear-geometry occurs at central-atoms with two bonded-atoms and zero or three lone-pairs (AX2 or AX2E3) in the AXE notation. Neutral AX2 molecules with linear-geometry include beryllium fluoride (F—Be—F) with two single-bonds,[1] carbon dioxide (O=C=O) with two double-bonds, hydrogen cyanide (H—C≡N) with one single and one triple-bond. The most important linear-molecule with more than three atoms is acetylene (H—C≡C—H), in which each of its carbon atoms is considered to be a central-atom with a single-bond to one hydrogen and a triple=bond to the other carbon atom. Linear-anions include azide (N3−) and thiocyanate (SCN−), and a linear-cation is nitronium ion (NO2+).[2]

Linear-geometry also occurs in AX2E3 molecules, such as xenon difluoride (XeF2)[3] and the triiodide-ion (I3−) with one iodide bonded to the two others. As described by the VSEPR model, the five-valence, electron-pairs on a central-atom form a trigonal bipyramid in which the three lone-pairs occupy the less crowded, equatorial-positions and the two bonded-atoms occupy the two axial-positions at the opposite-ends of an axis, forming a linear-molecule.

See also

References

  1. ↑ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 43. ISBN 978-0130399137.
  2. ↑ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
  3. ↑ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 47. ISBN 978-0130399137.

External links

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