Predict the ideal bond angle(s) around each central atom in this molecule.
Concepts and reason
The bond angle in any molecule depends on the shape of the molecule around the central atom. The shapes of molecules or ions can be explained based on valence shell electron pair repulsion (VSEPR) model. This model is mainly applicable to p-block elements.
The main postulates of VSEPR model is as follows:
- The shape of molecule depends on the electron-electron repulsions present in the valence shell of the central atom.
- The repulsive interactions between the electron pairs are in the following order:
- If the central atom forms multiple bonds, then the order of electron–electron repulsions between them is as follows:
The given molecule is as follows:
The ideal bond angle around carbon atom is and the ideal bond angle around oxygen atom is .
The oxygen atom has two sigma bonds and two lone pairs. Hence, according to VSEPR theory, the geometry at oxygen atom is tetrahedral and ideal bond angle is .
Each carbon atom has four sigma bonds and zero lone pairs. Hence, according to VSEPR theory, ideal bond angle at carbon atoms is .
Classify the structures as follows:
Here, Z represents the number of lone pair of electrons, Y represents the outer atoms (atoms other than central atom) and X represents the central atom. The structures are classified based on VSEPR theory.
The structure of glycine is as follows:
Depends on the number of lone pair of electrons and the number of sigma bonds around each atom, label the molecular shape around each central atom as follows:
In glycine, the nitrogen atom has one lone pair and three sigma bonds. Hence, according to VSEPR theory, the shape around nitrogen atom is trigonal pyramidal.
The oxygen atom has two lone pairs and two sigma bonds.
Hence, the shape around oxygen atoms is bent.
One carbon atom has four sigma bonds and zero lone pairs. For this carbon, the shape is tetrahedral.
The other carbon atom has three sigma bonds and zero lone pairs. Hence, according to VSEPR theory, the shape around this carbon is trigonal planar.