Final Answer:
The shape of AsH₃ is trigonal pyramidal. In the Lewis Dot structure of AsH₃, arsenic (As) is the central atom, surrounded by three hydrogen (H) atoms.
Step-by-step explanation:
To determine the molecular geometry, we consider the regions of electron density around the central atom. The central atom (As) has four regions of electron density, including three bonding pairs with hydrogen atoms and one lone pair. According to the VSEPR (Valence Shell Electron Pair Repulsion) theory, these electron pairs arrange themselves to minimize repulsion, resulting in a trigonal pyramidal geometry.
The lone pair exerts slightly greater repulsion than the bonding pairs, distorting the molecule's shape. This leads to a bond angle less than the ideal tetrahedral angle of 109.5 degrees. The actual bond angle in AsH₃ is approximately 92 degrees, giving it a trigonal pyramidal shape. The VSEPR theory helps predict the molecular geometry of molecules based on the arrangement of electron pairs, allowing us to understand the three-dimensional shape of AsH₃.
In summary, AsH₃ adopts a trigonal pyramidal shape due to the arrangement of electron pairs around the central arsenic atom. The lone pair introduces a distortion in the bond angle, resulting in a geometry that deviates from the ideal tetrahedral angle predicted by VSEPR theory.