How many non-bonding electrons (lone pair electrons) are on the central atom in the Lewis structure of NCl3
The Correct Answer and Explanation is:
Correct Answer: 2 non-bonding electrons (1 lone pair) on the central atom in the Lewis structure of NCl₃
Explanation:
To determine the number of non-bonding electrons on the central atom in nitrogen trichloride (NCl₃), we begin by examining the electron configuration and bonding behavior of the central atom, which is nitrogen.
Nitrogen is in group 15 of the periodic table. It has 5 valence electrons. In NCl₃, nitrogen forms three single covalent bonds with three chlorine atoms. Each chlorine atom contributes one electron to form a bond, so three of nitrogen’s five valence electrons are used in bonding.
This leaves nitrogen with two remaining valence electrons, which are not involved in bonding. These two electrons remain as a lone pair on the nitrogen atom. A lone pair consists of two electrons, and since nitrogen only has one such pair left after forming three bonds, the number of non-bonding electrons on nitrogen in NCl₃ is 2.
Visualizing the Lewis structure, nitrogen is at the center with three chlorine atoms surrounding it. Each N–Cl bond is a single pair of shared electrons. The nitrogen atom is surrounded by a total of four regions of electron density: three bonding pairs and one lone pair. This gives the molecule a trigonal pyramidal shape, based on the tetrahedral electron-pair geometry predicted by VSEPR (Valence Shell Electron Pair Repulsion) theory.
The presence of the lone pair on nitrogen slightly distorts the geometry from perfect tetrahedral, giving it the characteristic bent or pyramidal shape. The lone pair also affects the polarity and reactivity of the molecule.
In conclusion, nitrogen in NCl₃ has one lone pair, which is made up of two non-bonding electrons.
