H2S Molecular Geometry - Science Education and Tutorials

Q: What is the molecular notation for H2S molecule?

H2S molecular notation is AX2N2.

Hydrogen sulfide(H2S) has the composition of one sulfur and two hydrogen atoms. What is the molecular geometry of hydrogen sulfide?. Drawing and predicting the H2S molecular geometry is very easy by following the given method. Here in this post, we described step by step to construct H2S molecular geometry. Sulfur and hydrogen come from the 16th and 1st family groups in the periodic table. Sulfur and hydrogen have six and one valence electrons respectively.

Table of Contents

Key Points To Consider When drawing The H2S Molecular Geometry

A three-step approach for drawing the H2S molecular can be used. The first step is to sketch the molecular geometry of the H2S molecule, to calculate the lone pairs of the electron in the central sulfur atom; the second step is to calculate the H2S hybridization, and the third step is to give perfect notation for the H2S molecular geometry.

The H2S molecular geometry is a diagram that illustrates the number of valence electrons and bond electron pairs in the H2S molecule in a specific geometric manner. The geometry of the H2S molecule ion can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory) and molecular hybridization theory, which states that molecules will choose the H2S geometrical shape in which the electrons have from one another in the specific molecular structure.

Finally, you must add their bond polarities characteristics to compute the strength of the two S-H single bonds (dipole moment properties of the H2S molecular geometry). Two sulfur-hydrogen single bonds in the hydrogen sulfide(H2S), for example, are polarised toward the more electronegative value sulfur atoms, and because all two (S-H) single bonds have the same size and polarity, their sum is nonzero due to the H2S molecule’s bond dipole moment due to pulling the electron cloud to the two side of tetrahedral geometry, and the H2S molecule is classified as a polar molecule.

The molecule of hydrogen sulfide(with tetrahedral shape H2S molecular geometry) is tilted at 92 degrees bond angle of H-S-H. It has a difference in electronegativity values between sulfur and hydrogen atoms, with sulfur’s pull the electron cloud being greater than hydrogen’s. But bond polarity of S-H is not canceled to each other in the tetrahedral geometry. As a result, it has a nonzero permanent dipole moment in its molecular structure. The H2S molecule has a nonzero dipole moment due to an unequal charge distribution of negative and positive charges in the tetrahedral geometry.

Overview: H2S electron and molecular geometry

According to the VSEPR theory, the H2S molecule ion possesses tetrahedral molecular geometry. Because the center atom, sulfur, has two S-H single bonds with the two hydrogen atoms surrounding it. The H-S-H bond angle is 92.1 degrees in the tetrahedral H2S molecular geometry. The H2S molecule has a tetrahedral geometry shape because it contains two hydrogen atoms in the tetrahedral and two corners with two lone pairs of electrons.

There are two S-H single bonds at the H2S molecular geometry. After linking the two hydrogen atoms and two lone pairs of electrons on the sulfur atom in the tetrahedral form, it maintains the tetrahedral-shaped structure. In the H2S molecular geometry, the S-H single bonds have stayed in the two terminals and two lone pairs of electrons on the sulfur atom of the tetrahedral molecule.

The center sulfur atom of H2S has two lone pairs of electrons, resulting in tetrahedral H2S electron geometry. However, the molecular geometry of H2S looks tetrahedral or v-shaped and has two lone pairs of electrons on the sulfur of the H2S geometry. It’s the H2S molecule’s slight asymmetrical geometry. As a result, the H2S molecule is slightly polar.

How to find H2S hybridization and molecular geometry

Calculating lone pairs of electrons on sulfur in the H2S geometry:

1.Determine the number of lone pairs of electrons in the core sulfur atom of the H2S Lewis structure. Because the lone pairs of electrons on the sulfur atom are mostly responsible for the H2S molecule geometry planar, we need to calculate out how many there are on the central sulfur atom of the H2S Lewis structure.

Use the formula below to find the lone pair on the sulfur atom of the H2S molecule.
L.P(S) = V.E(S) – N.A(S-H)/2

Lone pair on the central sulfur atom in H2S = L.P(S)
The core central sulfur atom’s valence electron in H2S = V.E(S)
Number of S-H bonds = N.A (S-H)
calculation for sulfur atom lone pair in H2S molecule.

For instance of H2S, the central atom, sulfur, has six electrons in its outermost valence shell, two S-H single bond connections. This gives a total of two connections.

As a result of this, L.P(S) = (6 –2)/2=2

The lone pair of electrons in the sulfur atom of the H2S molecule is two.

Calculating lone pair of electrons on hydrogen in the H2S geometry:

Finding lone pair of electrons for the terminal hydrogen atom is not similar to the central sulfur atom. We use the following formula as given below

Use the formula below to find the lone pair on the hydrogen atom of the H2S molecule.
L.P(H) = V.E(H) – N.A(S-H)

Lone pair on the terminal hydrogen atom in H2S = L.P(H)
Terminal hydrogen atom’s valence electron in H2S = V.E(H)
Number of S-H bonds = N.A ( S-H)
calculation for hydrogen atom lone pair in H2S molecule.

For instance of H2S, their terminal atoms, hydrogen, have one electron in its outermost valence shell, one S-H single bond connection. This gives a total of two S-H single bond connections. But we are considering only one connection for the calculation.

As a result of this, L.P(H) = (1 –1)=0

The lone pair of electrons in the hydrogen atom of the H2S molecule is zero. Two hydrogen atoms are connected with the central sulfur atom.

In the H2S electron geometry structure, the lone pairs on the central sulfur atom are two, lone pairs of electrons in the hydrogen atom have zero. Two hydrogen atoms have no lone pairs of electrons.

It means there are two lone pairs of electrons in the core sulfur atom. Two lone pair of electrons on the central sulfur atom is responsible for the tetrahedral nature of H2S molecular geometry. But in the structure hydrogen atoms are polarised sidewise in their tetrahedral geometry.

The two lone pairs of electrons are placed at another side of the H2S geometry. Because the hydrogen atom is a lower electronegative value as compared with other atoms in the H2S molecule. Two hydrogen atoms are polarized towards the sidewise in the H2S structure.

But in reality, the H2S has two lone pairs of electrons in its structure. This makes the H2S more asymmetrical in the structure of the molecule. Because there is electric repulsion between bond pairs and lone pairs.

But some sort of interaction is there between hydrogen empty hole and lone pairs of electrons of sulfur of another H2S molecule. Here, hydrogen of one molecule acts as an acceptor and sulfur of another molecule as a donor. This is called hydrogen bonding between the two H2S molecules. This is one of the main intermolecular forces in H2S.

But in the central, sulfur atom has two lone pairs of electrons and these lone pair electrons just oppose each other with Sulfur- hydrogen bond pairs.

Calculate the number of molecular hybridizations of the H2S molecule

What is H2S hybridization? This is a very fundamental question in the field of molecular chemistry. All the molecules are made of atoms. In chemistry, atoms are the fundamental particles. There are four different types of orbitals in chemistry. They are named s, p, d, and f orbitals.

The entire periodic table arrangement is based on these orbital theories. Atoms in the periodic table are classified as follows:

s- block elements
p- block elements
d-block elements
f-block elements
Atoms are classified in the periodic table

H2S molecule is made of one sulfur, two hydrogen atoms. The hydrogen and sulfur atoms have s and p orbitals. But hydrogen atom has only s orbital in the ground state. Hydrogen comes as the first element in the periodic table. The sulfur atom also belongs to the oxygen family group. But it falls as the second element in the periodic table.

When these atoms combine to form the H2S molecule, its atomic orbitals are mixed and form unique molecular orbitals due to hybridization.

How do you find the H2S molecule’s hybridization? We must now determine the molecular hybridization number of H2S.

The formula of H2S molecular hybridization is as follows:
No. Hyb of H2S= N.A(S-H bonds) + L.P(S)
No. Hy of H2S = the number of hybridizations of H2S
Number of S-H bonds = N.A (S-H bonds)
Lone pair on the central sulfur atom = L.P(S)
Calculation for hybridization number for H2S molecule

In the H2S molecule, sulfur is a core central atom with two hydrogen atoms connected to it. It has two lone pairs of electrons on sulfur. The number of H2S hybridizations (No. Hyb of H2S) can then be estimated using the formula below.

No. Hyb of H2S= 2+2=4

The H2S molecule ion hybridization is four. The sulfur and hydrogen atoms have s and p orbitals. The sp3 hybridization of the H2S molecule is formed when one s orbital and three p orbitals join together to form the H2S molecular orbital.

Molecular Geometry Notation for H2S Molecule :

Determine the form of H2S molecular geometry using VSEPR theory. The AXN technique is commonly used when the VSEPR theory is used to calculate the shape of the H2S molecule.

The AXN notation of H2S molecule is as follows:
The central sulfur atom in the H2S molecule is denoted by the letter A.
The bound pairs (two S-H bonds) of electrons to the core sulfur atom are represented by X.
The lone pairs of electrons on the central sulfur atom are denoted by the letter N.
Notation for H2S molecular geometry

We know that H2S is the core atom, with two electron pairs bound (two S-H) and two lone pairs of electrons. The general molecular geometry formula for H2S is AX2N2.

According to the VSEPR theory, if the H2S molecule ion has an AX2N2 generic formula, the molecular geometry and electron geometry will both be tetrahedral or V-bent-shaped forms.

Name of Molecule	Hydrogen sulfide
Chemical molecular formula	H2S
Molecular geometry of H2S	Tetrahedral
Electron geometry of H2S	Tetrahedral
Hybridization of H2S	sp3
Bond angle (H-S-H)	92.1º degree
Total Valence electron for H2S	8
The formal charge of H2S on sulfur	0

Summary:

In this post, we discussed the method to construct H2S molecular geometry, the method to find the lone pairs of electrons in the central sulfur atom, H2S hybridization, and H2S molecular notation. Need to remember that, if you follow the above-said method, you can construct the H2S molecular structure very easily.