Question

Draw the Lewis structure for \(\mathrm{NF}_{3}\). What are its electronpair and molecular geometries? What is the hybridization of the nitrogen atom? What orbitals on \(\mathrm{N}\) and \(\mathrm{F}\) overlap to form bonds between these elements?

Short answer

NF3 is trigonal pyramidal with N exhibiting \(sp^3\) hybridization, and its bonds are formed by \(sp^3\) of N overlapping with \(p\) of F.

Step-by-step solution

Determine the Total Number of Valence Electrons

Nitrogen (N) has 5 valence electrons, and each fluorine (F) has 7 valence electrons. Calculate the total number of valence electrons using the formula: \[ 5 + 3 \times 7 = 26 \] Hence, NFe 3 has 26 valence electrons.

Draw the Skeleton Structure

Write the elements involved, with nitrogen (N) in the center and three fluorine atoms (F) surrounding it: \[ N-F-F-F \] This is because nitrogen is less electronegative and can form multiple bonds.

Distribute the Electrons

Begin by forming single bonds between the nitrogen and each fluorine atom:Each N-F bond uses 2 electrons, totaling 6 electrons for the 3 bonds. There are now \( 26 - 6 = 20 \) electrons remaining. Distribute these electrons to complete the octet for each fluorine atom (each needing 8 electrons around them).

Complete the Octet for Fluorine Atoms

Assign lone pairs to each fluorine until they each have an octet (8 electrons). Each fluorine uses 6 additional electrons as lone pairs:\[6 \times 3 = 18 \text{ electrons} \] This fits perfectly, as we had 20 electrons at the start of this step, so 2 electrons remain on nitrogen as a lone pair after accounting for the bonds and full octets on fluorine.

Assign the Remaining Electrons to the Central Atom

The two remaining electrons are placed as a lone pair on the nitrogen atom. With both the bonded pairs and the lone pair, nitrogen also completes its octet.

Determine the Electron Pair and Molecular Geometries

NF e 3 has a total of 4 electron groups (3 bonding and 1 lone pair) around the nitrogen atom. This results in an electron pair geometry that is tetrahedral. The presence of one lone pair makes the molecular geometry 'trigonal pyramidal'.

Find the Hybridization of Nitrogen

The 4 electron groups around the nitrogen require hybrid orbitals that accommodate these pairs, leading to \( sp^3 \) hybridization.

Determine Orbital Overlap

The bonds between nitrogen and fluorine are formed by the overlap of nitrogen’s \( sp^3 \) hybrid orbitals and fluorine’s \( p \) orbitals.

Key concepts

Electron Pair Geometry

In chemistry, the electron pair geometry pertains to the spatial arrangement of electron groups around a central atom. For the molecule \(NFe_3\), the nitrogen atom serves as the central hub. We count all regions of electron density—which include bonding pairs and lone pairs of electrons—around this atom.
In our exercise, we identified a total of 4 electron groups: 3 bonded pairs and 1 lone pair.
The lone pair and the bonded pairs create a shape known as tetrahedral when considering electron pair geometry.
This shape is important because it minimizes electron repulsion, helping to define the three-dimensional structure of the molecule.

Molecular Geometry

While electron pair geometry considers all electron groups, molecular geometry focuses solely on the arrangement of atoms.
Here, with \(NFe_3\), the lone pair on the nitrogen does affect the overall shape but isn’t part of the molecular geometry directly.
The three bonding pairs of nitrogen to fluorine produce a 'trigonal pyramidal' layout.
Unlike a tetrahedron, where empty space and atoms are evenly distributed, the trigonal pyramidal shape considers the lone pair "pushing" the fluorine atoms into this specific configuration.
Understanding molecular geometry helps predict molecular behavior, such as polarityand reactions with other compounds.

Hybridization

Hybridization is a concept that explains how atomic orbitals mix to form new hybrid orbitals, suitable for pairing with electrons from other atoms. For \(NFe_3\), let's consider the nitrogen atom with its 4 electron groups.
These groups utilize four hybrid orbitals, making the hybridization type \(sp^3\).
In the \(sp^3\) configuration, one s and three p orbitals blend to form a set of equivalent energy orbitals, forming the backbone for tetrahedral electron pair geometry.
This hybridization allows for optimal bonding and spatial distribution, ensuring the molecule remains stable and ideally structured.

Orbital Overlap

The concept of orbital overlap is central to understanding how bonds form between atoms.
In \(NFe_3\), each nitrogen–fluorine bond arises from the interplay between orbitals.
Nitrogen's \(sp^3\) hybrid orbitals overlap with the fluorine's 2p orbitals.
This overlap creates a covalent bond, characterized by shared electrons.
Each overlap forms a sigma bond, providing a robust connection due to the head-on interaction of orbitals.
Comprehending orbital overlap helps clarify the strength and nature of bonds in molecular structures.