What is the molecular shape of HCN?
A. Bent
B. Linear
C. Angular
D. Trigonal pyramidal
The Correct Answer and Explanation is:
The correct answer is B. Linear.
Explanation:
The molecular shape of hydrogen cyanide (HCN) can be determined by examining its molecular geometry based on the arrangement of its constituent atoms and the hybridization of its central atom. HCN consists of one hydrogen (H) atom, one carbon (C) atom, and one nitrogen (N) atom, with the carbon atom acting as the central atom in the molecule.
- Lewis Structure: To understand the molecular shape, we start by drawing the Lewis structure. Carbon (C) has four valence electrons, hydrogen (H) has one, and nitrogen (N) has five. To achieve stability, carbon forms a triple bond with nitrogen (sharing three pairs of electrons) and a single bond with hydrogen. The resulting structure shows that carbon is bonded to hydrogen and nitrogen with a triple bond.
- Hybridization: The carbon atom in HCN undergoes sp hybridization. In this process, one s orbital and one p orbital combine to form two equivalent sp hybrid orbitals. These hybrid orbitals are arranged linearly, resulting in a 180-degree bond angle between the atoms.
- Molecular Geometry: Due to the linear arrangement of the sp hybridized orbitals, HCN adopts a linear molecular shape. The triple bond between carbon and nitrogen means that the molecule extends in a straight line, minimizing the repulsion between electron pairs around the carbon atom.
- Visual Representation: In a linear shape, the atoms are arranged in a straight line: H–C≡N. This geometry allows the molecule to have distinct physical and chemical properties, influencing its behavior in various reactions.
In conclusion, the molecular shape of HCN is linear due to the sp hybridization of the carbon atom and the presence of a triple bond between carbon and nitrogen, resulting in a straight molecular configuration.