What is the shape of HCN? What is the angle of HCN?
The Correct Answer and Explanation is:
The shape of HCN (hydrogen cyanide) is linear, and the bond angle is 180°.
Explanation:
Hydrogen cyanide consists of three atoms: hydrogen (H), carbon (C), and nitrogen (N), arranged in a simple molecule. The structure of HCN can be drawn as:
H−C≡N\text{H} – \text{C} \equiv \text{N}H−C≡N
- Bonding in HCN:
- The carbon atom in HCN is sp hybridized, which means it forms two sigma bonds: one with the hydrogen atom and the other with the nitrogen atom.
- The nitrogen atom forms a triple bond with the carbon atom, consisting of one sigma bond and two pi bonds.
- Electron Geometry and Molecular Geometry:
- Since carbon is sp hybridized, it has two electron regions (one for the C-H bond and one for the C≡N bond). This results in a linear electron geometry.
- The molecular geometry also reflects this linearity, with the hydrogen and nitrogen atoms positioned on opposite sides of the carbon atom.
- Bond Angle:
- In a linear molecule, the ideal bond angle between the atoms is 180°. In HCN, this ideal bond angle is observed because of the sp hybridization of the carbon atom, which forces the atoms to be as far apart as possible, resulting in a straight line.
This linear structure and 180° bond angle are characteristic of molecules where the central atom has sp hybridization, which minimizes electron repulsion between the bonds, leading to a stable molecular shape.
