Intermolecular Forces of H2S (Strong or Weak)

Hydrogen sulphide is a colourless chalcogen-hydride gas that is caustic, poisonous, and flammable. The chemical formula H2S is used to describe it, and it has a rotten egg odour. Volcanic gases, natural gas, hot springs, and crude petroleum all contain it.

It is also formed as a byproduct of bacteria’ anaerobic decomposition of organic materials. In the presence of oxygen, it burns to produce sulphur dioxide and water. Sulfur, alkali metal sulphides, and thio organic compounds are all made from it. In analytical chemistry, it’s also utilised for qualitative inorganic analysis of metal ions. Sewer gas or stink damp are some names for it.

Hello there, everyone!!! We’re back with another fascinating topic for you.

We’ll discuss about hydrogen sulphide and intermolecular forces in this article. So, let’s get started.

So, what kinds of intermolecular forces does H2S have?

Intermolecular forces between hydrogen sulphide molecules include dipole-dipole interactions and London dispersion forces.

Hydrogen has an electronegativity of 2.2, while sulphur has an electronegativity of 2.38. The electrons shared in the formation of the bond move slightly towards sulphur due to this minor difference in electronegativity. As a result, the hydrogen and sulphur ends of the molecules develop positive and negative poles, respectively. As a result, the dipole-dipole interaction between the molecules develops.

The London dispersion forces exist between H2S molecules as well. These are, however, the weakest of all intermolecular interactions and have no effect on a molecule’s characteristics.

Why does H2S exist as a gas whereas H2O exists as a liquid?

In comparison to hydrogen bonding between water molecules, the intermolecular interactions operating between H2S molecules are dipole-dipole forces that are quite weak.

The electronegativity differential between the atoms that make up a molecule causes the dipole-dipole interaction.

A small negative charge emerges on the more electronegative atom as it pushes the shared electron pair slightly towards itself.

A polar covalent bond is established as a result of the establishment of a little positive charge on the lesser electronegative atom.

Furthermore, due to charge separation within the molecule, opposite poles form, resulting in the dipole-dipole interaction.

However, because the electronegativity difference between hydrogen (2.2) and sulphur (2.38) atoms is fairly small, the forces created to keep the molecules together are not as strong.

As a result, the molecules are more or less free to move away from one another, resulting in the formation of H2S as a gas.

The London dispersion forces are another form of force known to exist between hydrogen sulphide molecules.

These are quite weak in nature and occur in practically all molecules, therefore they don’t play a big influence in determining a molecule’s state of occurrence.

The H2O molecules, on the other hand, are held together by hydrogen bonding, a strong intermolecular force.

The electronegativity of hydrogen (2.2) and oxygen (3.44) atoms is vastly different. On the two ends of the molecules, this results in the development of distinct poles.

These poles attract the opposing poles of other molecules, i.e. the partially positive hydrogen atoms of one molecule attract the partially negative oxygen atom. As a result, strong bonds are formed between distinct molecules.

As a result, the H2O molecules remain closer together, and water remains in a liquid form.

Intermolecular Forces Types

Intermolecular forces are the forces of attraction that occur between various molecules of a substance when they are positioned close together.

Electrostatic interactions, for the most part, play a role in establishing the state in which a compound will exist. Dipole-dipole interaction, hydrogen bonding, and so on.

They’re not the same as intramolecular forces, which exist between two or more atoms within the same molecule.

Intramolecular forces may play a role in determining the intermolecular forces that emerge between molecules.

An ionic or polar covalent bond, for example, frequently results in a dipole-dipole interaction.

The following are examples of intermolecular forces:

• Electrostatic forces of attraction between two or more ions are known as ion-ion forces. Ion-ion forces are formed when oppositely charged ions are attracted to each other.

• Ion-dipole moment: A polar and an ionic molecule have this form of intermolecular force.

A positive ion is drawn to the slight negative end of a polar molecule in this situation. A negative ion is drawn to the slightly positive end of a polar molecule in the same way.

Salt dissolved in water is a famous illustration of these forces. The salt generates ions that bind to the water’s polar molecules.

• Dipole-dipole interaction: These are the forces that occur between the polar molecules, as mentioned in the example of H2S. The difference in electronegativity of the combining atoms, such as between hydrogen and sulphur, causes polarity.

In a polar covalent bond, these forces emerge when a slight positive and slight negative charge builds on the two ends of a molecule. Molecules attract one other and are drawn to the opposite poles of other molecules.

The HCl compound is another example of a compound with dipole forces among its components. Check out the HCl Intermolecular Forces article.

• Hydrogen Bonding: These interactions are more powerful than dipole-dipole interactions. These forces also occur between a compound’s polar molecules.

The sole requirement is that the electronegativity gap between the atoms be significant. As a result, hydrogen bonding is limited to molecules containing hydrogen bound to oxygen, nitrogen, or fluorine.

• Intermolecular forces of London dispersion: These are the weakest intermolecular forces. These can be found in all molecules, but they aren’t strong enough to hold them together. Induced dipole-induced dipole forces are another name for them.

These forces are mainly caused by the formation of transient poles within a molecule.

The poles may form as a result of the molecule’s temporary induced charge interacting with the other molecule’s similar temporary charge. As a result, the nomenclature induced dipole-induced dipole was coined.

The many types of intermolecular forces are ranked in decreasing order of strength.

Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces > Ion – Ion > Ion – Dipole > Hydrogen Bonding > Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces

Why Doesn’t H2S Have Hydrogen Bonding?

The specific intermolecular force that only exists between molecules in which hydrogen atoms are bound to a strongly electronegative atom such as fluorine, oxygen, or nitrogen is known as hydrogen bonding.

The opposite poles form on the molecule due to the huge difference in electronegativity of these atoms.

As in the case of dipole-dipole interaction, the more electronegative atom obtains a slightly negative charge whereas the less electronegative atom acquires a positive charge.

Because the electronegativity difference is so great, the poles practically behave like an ion. They have significant attraction strengths towards molecules with opposing poles.

As a result, high electrostatic interactions exist between the molecules of these compounds, causing them to stick together. Water, hydrogen fluoride, and ammonia have a liquid state and a high melting point due to this.

In the case of H2S, however, the electronegativity difference between the hydrogen and sulphur atoms is insufficient to create strong and stable poles. As a result, hydrogen sulphide lacks hydrogen bonding.

Is there a dipole moment in H2S?

The hydrogen and sulphur atoms in the hydrogen sulphide molecule are joined by a polar covalent link. The two opposite poles arise inside the molecule due to the electronegativity mismatch between these two atoms.

A molecule’s polarity is measured by its dipole moment. H2S is a polar molecule, despite the tiny electronegativity difference between the hydrogen (2.2) and sulphur (2.38) atoms.

In the case of H2S, the dipole moment is 0.97 D.


Is H2S an ionic or a covalent gas?

The sharing of electrons participating in the formation of a bond forms a covalent bond. H2S is a covalent molecule because the valence electrons of sulphur and oxygen involved in bond formation are shared between these atoms.

Is hydrogen sulphide (H2S) a binary compound?

Binary compounds are made up of two components combined together. H2S is a binary chemical, meaning it is made up of hydrogen and sulphur atoms.

H2S is a type of acid, but what kind of acid is it?

Answer: H2S is a weak acid since its acid dissociation constant is low. It exists as a gas with a pKa value of 6 to 7.

H2S Characteristics

The following are some of the most important features of hydrogen sulphide:

• H2S has a molecular mass of 34.08 gm/mol.

• It’s a colourless, pungent-smelling gas with a rotten-egg-like odour.

• H2S has a density of 1.363 gm/dm3.

• Hydrogen sulphide has melting and boiling temperatures of 82°C and -60°C, respectively.

• The molecule has a dipole moment of 0.97D and is bent in form.


Dipole-dipole and London dispersion forces function as intermolecular forces of attraction between H2S molecules.

The electronegativity mismatch between the joining atoms causes the dipole-dipole interaction.

The following is a list of the intermolecular forces in decreasing order of strength:

Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces > Ion – Ion > Ion – Dipole > Hydrogen Bonding > Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces

Read more: Is PBr3 a polar or nonpolar substance?

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.


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