The Lewis dot structure of ammonia, NH3, reveals that it has one lone pair of electrons and three bonds (each to a hydrogen) around the central nitrogen atom. According to VSEPR theory, what molecular shape will it have?

i thought it was tetrahedral but its wrong. what and why is the answer.

There are two answers. The ELECTRONIC GEOMETRY is tetrahedral; the molecular geometry is trigonal pyramidal.

Look at the AB3E here.
http://chemlabs.uoregon.edu/GeneralResources/models/vsepr.html

The correct molecular shape of ammonia (NH3) according to the VSEPR (Valence Shell Electron Pair Repulsion) theory is trigonal pyramidal.

In the VSEPR theory, lone pairs and bonding electron pairs around the central atom influence the molecular shape by trying to maximize the distance between them to minimize electron-electron repulsion.

Ammonia has four electron regions around the nitrogen atom: three bonding pairs (each connecting to a hydrogen atom) and one lone pair. The lone pair of electrons has slightly greater repulsion compared to bonding pairs because it is not shared with another atom. Therefore, the lone pair will occupy more space, "pushing" the bonding electron pairs closer together.

The result is a trigonal pyramidal molecular shape, where the three hydrogen atoms are arranged roughly in a triangular formation around the central nitrogen atom, with the lone pair occupying the fourth position, giving it a pyramidal shape.

According to VSEPR (Valence Shell Electron Pair Repulsion) theory, the molecular shape is determined by the arrangement of bonding and lone electron pairs around the central atom. In the case of ammonia (NH3), we have one lone pair and three bonds.

To determine the molecular shape, we start by drawing the Lewis dot structure of ammonia:

N
:
H - N - H
:

In this structure, the nitrogen atom is represented by an "N" and is surrounded by three hydrogen atoms ("H").

Since there is one lone pair of electrons on the nitrogen atom, we consider it as an electron domain. The three bonds between nitrogen and hydrogen are also considered electron domains.

Now, we need to determine the electron-domain geometry, which represents the arrangement of all the electron domains around the central atom. For ammonia, we have a total of 4 electron domains (1 lone pair + 3 bonds).

The possible electron domain geometries are:
1. Linear (2 electron domains)
2. Trigonal Planar (3 electron domains)
3. Tetrahedral (4 electron domains)
4. Trigonal Bipyramidal (5 electron domains)
5. Octahedral (6 electron domains)

Since ammonia has 4 electron domains, the electron-domain geometry possibilities are tetrahedral, trigonal planar, and linear.

However, the molecular shape is determined by considering the arrangement of the bonded atoms only, not the lone pairs. The lone pairs tend to occupy more space, causing the bonded atoms to squeeze closer to each other.

In ammonia, the lone pair repels the bonded pairs, creating a slightly compressed tetrahedral shape. This is called "pyramidal" geometry. Therefore, the molecular shape of ammonia is "pyramidal" with a bent appearance.

In summary, the molecular shape of ammonia (NH3) is "pyramidal" due to the presence of one lone pair and three bonded pairs around the central nitrogen atom.