Q10.33P - Chemistry: Molecular Nature Of Matter And Change

Question

What would you expect to be the electron-group arrangement around atom A in each of the following cases? For each arrangement, give the ideal bond angle and the direction of any expected deviation:

Step-by-Step Solution

Answer

The shapes and bond angles of molecules can be determined from the VSEPR theory. The deviations arise mainly due to lone pair-lone pair repulsions.

Step 1: Trigonal Planar

The expected arrangement would be trigonal planar around the central atom A. Ideal bond angle expected would be ${\mathbf{120}}^0$. Since a lone pair is present, the angle will decrease from ${\mathbf{120}}^0$ .

Step 2: Linear

The expected arrangement would be linear around the central atom A. Ideal bond angle would be ${\mathbf{180}}^0$

Step 3: Trigonal Planar

The expected arrangement would be trigonal planar around the central atom A. Ideal bond angle would be ${\mathbf{120}}^0$

Step 4: Linear

The expected arrangement would be linear around the central atom A. Ideal bond angle would be ${\mathbf{180}}^0$. The lone pairs around the central metal would cause repulsion and decrease the value from the expected value. 

Step 5: Linear

The expected arrangement would be linear around the central atom A. Ideal bond angle would be ${\mathbf{180}}^0$.

Step 6: T-shaped

The expected arrangement would be T-shaped around the central atom A. The geometry is trigonal bipyramidal. Ideal bond angles would be ${\mathbf{180}}^0$ and ${\mathbf{120}}^0$^.The bond angle between the planar atoms would decrease from ${\mathbf{120}}^0$  due to presence of the lone pair.