What is the molecular shape of an ammonia molecule, NH3? bent linear Trigonal Pyramidal Tetrahedral
The Correct Answer and Explanation is:
The correct molecular shape of an ammonia (NH₃) molecule is Trigonal Pyramidal.
Ammonia consists of one nitrogen atom bonded to three hydrogen atoms. To understand its shape, we use the Valence Shell Electron Pair Repulsion (VSEPR) theory, which predicts the shape of molecules based on the repulsion between electron pairs in the valence shell of the central atom.
Nitrogen has five valence electrons. In NH₃, three of these electrons form single covalent bonds with three hydrogen atoms. This leaves one lone pair of electrons on the nitrogen atom. According to VSEPR theory, both bonding pairs and lone pairs of electrons repel each other and try to stay as far apart as possible to minimize repulsion. However, lone pairs repel more strongly than bonding pairs because lone pairs are not shared between atoms and occupy more space.
If nitrogen had four bonding pairs and no lone pairs, as in methane (CH₄), the molecule would adopt a tetrahedral shape. In ammonia, however, one of these positions is occupied by a lone pair. The result is a shape that resembles a tetrahedron but is slightly distorted. The three hydrogen atoms and the lone pair form a tetrahedral electron geometry, but the molecular geometry (which only considers the positions of atoms, not lone pairs) is described as trigonal pyramidal.
The presence of the lone pair causes the bond angles to shrink slightly from the ideal tetrahedral angle of 109.5 degrees. In NH₃, the H-N-H bond angles are approximately 107 degrees. This slight reduction is due to the lone pair pushing the bonding pairs closer together.
In summary, ammonia has a trigonal pyramidal molecular shape because of the three bonding pairs and one lone pair on the central nitrogen atom. This arrangement leads to a three-sided pyramid shape with nitrogen at the apex and hydrogen atoms at the base.
