What is the molecular shape of HCN? bent linear angular trigonal pyramidal
The Correct Answer and Explanation is:
The molecular shape of HCN (Hydrogen Cyanide) is linear.
Here’s why:
- Lewis Structure of HCN: The molecule consists of a central carbon (C) atom bonded to a hydrogen (H) atom and a nitrogen (N) atom. The carbon atom forms a triple bond with nitrogen, and a single bond with hydrogen.
- Electron Groups: The carbon atom has two electron groups around it — one from the triple bond with nitrogen and the other from the single bond with hydrogen.
- VSEPR Theory (Valence Shell Electron Pair Repulsion): According to VSEPR theory, electron pairs (bonding or non-bonding) around a central atom arrange themselves in a way that minimizes repulsion. In the case of HCN, there are only two bonding pairs around carbon, which would place them as far apart as possible, resulting in a linear arrangement.
- Bond Angles: In a linear geometry, the bond angle between the atoms is 180°.
- Molecular Shape: The presence of just two bonding pairs and no lone pairs on the central carbon atom dictates a linear shape, not angular, bent, or trigonal pyramidal.
In summary, because the electron pairs around carbon are spread out in a linear arrangement, the molecular geometry of HCN is linear, with a bond angle of 180°. The triple bond between carbon and nitrogen is particularly strong and influences the overall shape, leading to this geometry.
