The shape of the ammonia NH3 molecule is trigonal pyramidal. This molecular geometry is determined by the presence of one nitrogen atom at the center, bonded to three hydrogen atoms, and one lone pair of electrons on the nitrogen atom.The polarity of the ammonia molecule is due to the difference in electronegativity between the nitrogen and hydrogen atoms. Nitrogen is more electronegative than hydrogen, which means it attracts the shared electrons in the N-H bond more strongly. This results in a partial negative charge on the nitrogen atom and partial positive charges on the hydrogen atoms. The presence of the lone pair of electrons on the nitrogen atom also contributes to the overall polarity of the molecule.The molecular geometry and polarity of ammonia are influenced by the following factors:1. Electron pair repulsion: The lone pair of electrons on the nitrogen atom repels the bonding pairs of electrons between the nitrogen and hydrogen atoms. This repulsion causes the bonding pairs to be pushed further apart, resulting in the trigonal pyramidal shape.2. Electronegativity difference: The difference in electronegativity between nitrogen and hydrogen leads to the formation of polar covalent bonds. This creates a molecular dipole moment, making ammonia a polar molecule.3. Valence shell electron pair repulsion VSEPR theory: According to VSEPR theory, the electron pairs around the central atom both bonding and non-bonding repel each other and arrange themselves in a way that minimizes this repulsion. In the case of ammonia, the three bonding pairs and one lone pair adopt a tetrahedral arrangement, but the molecular shape is trigonal pyramidal due to the presence of only three atoms bonded to the central nitrogen atom.