Molecules. Types, structure, and geometry of molecules

07/05/2026

The online molecules simulations on this page illustrate in an interactive way how a molecule is constructed and what are its main characteristics. We will learn about molecular structure, types of molecules, the geometry of molecules and what polarity of a molecule consists of and how it acts.

This Thematic Unit is part of our Chemistry collection

Bond Angle

Angle formed by two chemical bonds sharing the same central atom. The unit of measurement is the sexagesimal degree (°).

Bond Length

Average distance between the nuclei of two atoms joined by a chemical bond. It is usually measured in angstroms (Å) or picometers (pm).

Intermolecular Forces

Electrostatic attractions that act between adjacent molecules and determine physical properties such as the state of matter.

Molecular Formula

Chemical expression indicating the exact number and type of atoms that make up a specific molecule.

Molecular Geometry

Spatial arrangement of atoms in a molecule, determined by bond angles and distances between nuclei.

Molecular Structure

Three-dimensional arrangement of the atoms that constitute a molecule and the nature of their spatial organization.

Molecule

Smallest particle of a substance that retains its chemical properties, formed by two or more bonded atoms.

What is a molecule

A molecule is the smallest unit of a substance that still retains the chemical and physical properties of that substance. It is composed of two or more atoms that are bonded together by chemical bonds to form a stable structure.

Structure of a molecule

The structure of a molecule can be linear, branched or three-dimensional, depending on how the atoms are bonded together. The arrangement of atoms in a molecule determines its physical and chemical properties, such as its melting point, boiling point, solubility, reactivity and polarity.

Types of molecules

There are different types of molecules that can be classified according to their chemical composition and function.

Organic molecules

They are mainly composed of carbon, hydrogen and oxygen atoms, although they can also contain other elements such as nitrogen, phosphorus, sulfur and halogens. Examples of organic molecules include carbohydrates, lipids, proteins and nucleic acids.

Inorganic molecules

These are molecules that do not contain carbon and are generally simpler in structure than organic molecules. Examples of inorganic molecules include water (H₂O), carbon dioxide (CO₂), salts and minerals.

Biomolecules

These are molecules found in living things that perform essential functions in biological processes. Biomolecules include proteins, carbohydrates, lipids and nucleic acids.

Simple molecules

These are molecules composed of only one type of atom. Examples of simple molecules include oxygen (O₂), nitrogen (N₂) and chlorine (Cl₂).

Complex molecules

These are molecules composed of two or more types of atoms. Examples of complex molecules include glucose (C₆H₁₂O₆), hydrochloric acid (HCl) and ammonia (NH₃).

Bond Angle

Angle formed by two chemical bonds sharing the same central atom. The unit of measurement is the sexagesimal degree (°).

Bond Length

Average distance between the nuclei of two atoms joined by a chemical bond. It is usually measured in angstroms (Å) or picometers (pm).

Intermolecular Forces

Electrostatic attractions that act between adjacent molecules and determine physical properties such as the state of matter.

Molecular Formula

Chemical expression indicating the exact number and type of atoms that make up a specific molecule.

Molecular Geometry

Spatial arrangement of atoms in a molecule, determined by bond angles and distances between nuclei.

Molecular Structure

Three-dimensional arrangement of the atoms that constitute a molecule and the nature of their spatial organization.

Molecule

Smallest particle of a substance that retains its chemical properties, formed by two or more bonded atoms.

Explore the exciting STEM world with our free, online, simulations and accompanying companion courses! With them you’ll be able to experience and learn hands-on. Take this opportunity to immerse yourself in virtual experiences while advancing your education – awaken your scientific curiosity and discover all that the STEM world has to offer!

Molecule simulations

3D Molecule Build

Learn with this 3D molecule build simulation. Starting from atoms, see how you can build many molecules. Gather your molecules and see them in 3D!

Geometry of molecules I

Explore the geometry of molecules by building molecules in 3D! Discover how the molecular geometry changes as atoms are added to it.

Geometry of molecules II

Explore the geometry of molecules by building 3D molecules! How does the molecular geometry change with different numbers of bonds and electron pairs? Find out by adding single, double or triple bonds and lone pairs to the central atom, then compare the model with real molecules!

Molecule polarity

The polarity of a molecule refers to the unequal distribution of electric charges within it, which can influence its chemical and physical interactions. This characteristic depends on the molecular geometry and the differences in electronegativity between its constituent atoms. When is a molecule polar? Change the electronegativity of the atoms in a molecule to see how it affects polarity. See how the molecule behaves in an electric field. Change the bond angle to see how it affects the polarity shape.

Giants of science

“If I have seen further, it is by standing on the shoulders of giants”

Isaac Newton

Dmitri Ivánovich Mendeleev

1834

–

1907

Dmitri Mendeleev formulated the periodic table of elements, organizing known ones and predicting unknown ones with remarkable accuracy.

“In science, truth is revealed sooner through errors than through confusions”

Robert Boyle

1627

–

1691

Robert Boyle formulated the first quantitative law of gases, showing the relationship between pressure and volume, laying foundations of modern chemistry and fluid mechanics

“Air is as necessary to life as food”

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“If I have seen further, it is by standing on the shoulders of giants”

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John Dalton

1766

–

1844

John Dalton formulated the first atomic theory, explaining the composition of matter and the law of multiple proportions in chemical compounds.

“Science is the foundation of truth”

Fritz Haber

1868

–

1934

Fritz Haber developed the Haber-Bosch process, enabling large-scale ammonia synthesis, revolutionizing fertilizer production and industrial chemistry

“Chemistry has the power to transform life on Earth”

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Test your knowledge

What is a molecule, and how is it defined in chemistry?

A molecule is the smallest unit of a substance that retains its chemical and physical properties. It is formed by two or more atoms joined together through chemical bonds that provide stability to the structure. These bonds may be covalent, polar or non‑polar, and they largely determine the molecule’s behavior. Molecules can be simple, such as oxygen (O₂), or complex, such as glucose (C₆H₁₂O₆). The spatial arrangement of atoms directly influences properties such as solubility, reactivity, boiling point and polarity. Understanding what a molecule is helps explain fundamental chemical phenomena, from the formation of compounds to interactions between substances. Molecular study is essential in biology, medicine, chemical engineering and materials science.

How is the structure of a molecule organized, and why is it important?

The structure of a molecule describes how atoms are arranged in space and how they are connected through chemical bonds. This structure may be linear, branched or three‑dimensional, depending on the types of atoms and the bonds between them. Molecular geometry directly influences properties such as polarity, reactivity, solubility and melting and boiling points. For example, symmetrical molecules tend to be non‑polar, while asymmetrical ones may be polar. Structure also determines how molecules interact with one another, affecting biological processes, chemical reactions and material behavior. Understanding molecular structure is essential for predicting properties, designing new compounds and explaining phenomena such as drug activity or crystal formation.

Why is the shape of a molecule important?

The shape of a molecule is important because it determines how it behaves and how it interacts with other substances. A molecule may be linear, flat or three‑dimensional, and that geometry affects its polarity, solubility and reactivity. In biology, many molecules fit together like puzzle pieces, so a small change in shape can completely alter their function. Shape also influences everyday properties such as smell, texture or the ability to mix with water. Understanding molecular shape helps explain why substances act the way they do.

What types of molecules exist according to their composition?

According to their composition, molecules can be classified as organic, inorganic, biomolecules, simple or complex. Organic molecules contain mainly carbon, hydrogen and oxygen, such as carbohydrates, lipids and proteins. Inorganic molecules generally do not contain carbon, such as water or salts. Biomolecules are essential for living organisms and include proteins, lipids, carbohydrates and nucleic acids. Simple molecules are made of a single type of atom, such as O₂ or N₂, while complex molecules contain several types of atoms, such as glucose or ammonia.

What distinguishes a simple molecule from a complex molecule?

A simple molecule is made of a single type of atom, such as oxygen (O₂) or nitrogen (N₂). These molecules usually have simpler structures and more uniform properties. A complex molecule, on the other hand, contains two or more types of atoms, such as glucose (C₆H₁₂O₆) or ammonia (NH₃). Their structure is more varied, and their properties may change depending on the arrangement of atoms. Complex molecules often participate in more elaborate biological and chemical processes, while simple molecules perform basic functions in nature.