Polarity, NH2 Lewis Structure, Molecular Geometry, and Hybridization

As can be observed, NH2 is composed of nitrogen and hydrogen atoms. However, this substance exists in multiple forms as chemical entities. As a neutral chemical, it is known to exist as an amino radical with the formula NH2.

Radicals are characterised by the presence of unpaired valence electrons, making them chemically reactive. This characteristic renders this radical impermanent (unless treated with certain organic molecules). It is the neutral form of amide or azanide ions and has a molar mass of around 16.0226 g/mol.

This essay will concentrate on the azanide anion (NH2-). NH2- is the conjugate base of ammonia and the conjugate acid of hydridonitrate (H-N2-) (NH3).

2Li + 2NH3 —–> 2LiNH2 + H2

This reaction illustrates how metal amides, such as Lithium Amide, are generated from ammonia solution and Li metal.

Azanide is an inorganic anion with a single, negative charge of -1.

NH2- is not stable in its natural state, hence it exists as a hydrazine compound.

Amidyl group (-NH-) and azanidylidene group (=N-) are azanide substituents. (The amidyl group is generated when NH2 loses a proton.)

Let us now go to our main issue and explore the chemical bonding nature of NH2-.

Lewis Structure of NH2

Drawing the Lewis Structure is the earliest and most crucial step in determining the bonding type of any chemical molecule structure.

Lewis Structure is a two-dimensional representation of the internal bonds between atoms in a molecule or ion. Before we can start to design the Lewis Structure of any given molecule, in this case the azanide ion, we must first grasp three fundamental ideas.

  1. Valence electrons and electron dot notations:

We understand what valency is. It is described as the ability of an atom to combine to form bond structures. When two atoms share electron pairs, they establish a chemical bond. Consequently, single, double, and triple bonds are possible.

Valence electrons are the electrons in an atomic nucleus’ outermost shell. When depicting the Lewis Structure, also known as the electron-dot structure, we represent these as dots. Straight lines are used to represent the bonds.

  1. Octet rule

If we examine the contemporary periodic table, we can see that the major group elements are distributed throughout groups 1 through 17. During bond formation, these elements tend to obtain the outer shell electronic configuration of noble gas elements, i.e., a valency of eight.

This is referred to as the octet rule or octet completion. There are, however, exceptions to this rule.

  1. Formal Cost

If we believe that electrons will always be shared in equal amounts between atoms during the formation of a molecule, then the formal charge is the electric charge assigned to each atom.

When determining the graphical representation of the molecule, it is essential to ensure that the atoms have the lowest feasible formal charge values.

Let’s start drawing Lewis structures for NH2 immediately.

Hydrogen belongs to period 1 and contains only one valence electron, whereas nitrogen belongs to period 15 and possesses five valence electrons.

Aside from this, we have an electron with a negative charge of -1.

The total number of valence electrons in an NH2- anion is equal to five plus two times one plus one, or eight.

In terms of electronegativity, Hydrogen is inferior to Nitrogen. In general, the atom with the lowest electronegativity is the centre atom.

Hydrogen, which has only one electron and is incapable of forming many covalent connections, does not survive or function as the centre atom.

In this example, nitrogen is the core atom.

We have positioned nitrogen-containing atoms in the centre.

All valence electrons have been positioned and labelled with dot notations.

The nitrogen atom has acquired octet configuration, as observed.

As an exception to the general octet rule, the arrangement of both hydrogen atoms is identical to that of helium.

Now, we must examine the formal charge values of each component atom.

The formal charge of N is equal to -1.

The formal charge of H is equal to zero.

As can be seen, the NH2 structure has a net negative charge.

NH2 Molecular Geometry

Do you aware that the Lewis Structure of a molecule can be used to predict its 3D molecular shape?

This requires an understanding of the theory of Valence Shell Electron Pair Repulsion, or VSEPR. According to this idea, because electrons are similar to charges, the negative cloud environment surrounding each atomic nucleus tends to suffer repulsion.

To stabilise a molecule’s structure, it is necessary to reduce the repulsion between electrons.

Verify the VSEPR notation for NH2-.

A is the central atom, X is the surrounding atoms or bound electron pairs of the central atom, and E is the lone pair on the central atom.

The nomenclature for azanide anion is AX2E2.

As seen in the preceding VSEPR diagram, NH2- has a bent molecular geometry.

It has a bond angle of 104.50, which is significantly less than the optimal value of 109.50. Due to the strong repulsive force of the two lone pairs on the core N atom, this occurs.

Atomic Geometry

Examining the Lewis Structure of the NH2- ion reveals four electron-rich areas surrounding the core nitrogen atom. There are two bound electron pairs surrounding the nitrogen atom, each of which forms a single covalent link with a hydrogen atom.

In addition, nitrogen has two unpaired or lone electron pairs. These four (bonded and unbonded) electron pairs result in a tetrahedral electron geometry.

NH2 Hybridization

In chemistry, orbital hybridization is an important topic. It is a mathematical model for describing covalent bonding.

As stated by Heisenberg’s Uncertainty Principle, we cannot predict the precise location of electrons near an atomic nucleus if we assume that electrons behave as both particles and waves.

Consequently, we discuss orbitals, which offer us an indication of the probability of electron presence in a geographical space.

Valence Bond Theory states that atomic orbitals of the same atom with equivalent energies combine to generate hybridised orbitals (VBT).

For instance, an’s’ and a ‘p’ orbital combine to make an’sp’ hybrid orbital, an’s’ and two ‘p’ orbitals (such as px and py) combine to form an’sp2′ hybrid orbital, and so on.

Let us see what NH2- ion hybridization is:

For determining hybridization, the following formula can be used:

H= 1/2 (V + M – C + A)

H = kind of hybridization

V equals the number of valence electrons

M= monovalent atoms

C equals cationic charge

A = anionic valence

Here, V=5 and M=2; C=0 and A=1;

H = ½(5 + 2 – 0 + 1) = 4.

Nitrogen atom has five valence electrons.

If we examine the electrical configuration of N, we observe the following:

N: 1s2 2s2 2p3

Not being an outer shell orbital, the 1s orbital does not participate in the hybridization. We just consider the electrons in the valence shell.

Consequently, the s orbital and three 2p orbitals (px, py, pz) combine to create sp3 hybrid

orbitals.

NH2 Polarization

Polarity is another crucial chemical concept that will be discussed in this article in relation to the NH2- ion. Polarity is the separation of charges within a molecule.

To determine the polarity of azanide, we must use the Pauling Electronegativity chart.

To determine whether a given molecule is polar or non-polar, it is necessary to understand electronegativity, i.e. the ability or degree of an atom to gain negatively charged electrons.

N possesses an electronegativity value of 3.04, while H possesses an electronegativity value of 2.20. Consequently, the vast disparity in electronegativity between the N-H bonds induces dipole moment.

It is determined by multiplying the charge by the distance between the two charges. Both ends will have half positive and negative charges (+ and -). Hence, polar bonds are created as a result.

For fundamental NH2 polarity reasons, you must investigate NH2 polarity.

Due to the presence of repulsive interactions via lone pairs as well as bond pairs, the molecule’s three-dimensional shape is not linear.

This also contributes to NH2- ion’s polar character.

Conclusion

This article describes the bonding characteristics of azanide and amide ions. We have covered the Lewis Structure, molecular geometry, Hybridization, and Polarity in our explanation.

Best wishes for learning chemistry!

Read more: The pH of Hydrogen Peroxide: Acidic or Basic?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

LEAVE A REPLY

Please enter your comment!
Please enter your name here

Read More

Recent