What is a molecule?

What is a molecule:in biology, in chemistry, in science, example. Molecules consist of two or more atoms of the same or different elements substituting for one another. In molecule form, atoms can be homonuclear, which is composed of an element of one type, like oxygen (O2), or heteronuclear is composed of an element of more than one type of element, like water (H2O).

What is a molecule:in biology, in chemistry, in science, example
What is a molecule:in biology, in chemistry, in science, example

Each molecule can be categorized based on its size, complexity, and shape. For example, helium consists of just one atom. A molecule is formed when two atoms of the same element combine. As an example, the oxygen molecule O2 occurs most frequently on earth; it is made up of two oxygen atoms.

A pair of oxygen atoms can, however, link into a triplet (O3) under certain conditions, which forms the molecule ozone. In contrast, carbon dioxide (CO2) consists of one carbon atom connected to two oxygen atoms, while water (H2O) contains two hydrogen atoms and one oxygen atom. In sulfuric acid, four oxygen atoms make up the structure (H2SO4), with two hydrogen atoms and one sulfur atom.

It is impossible to stop molecules from moving. All solids and liquids contain molecules tightly packed together. The mobility of molecules in a solid can be compared to fast vibration. In a liquid, molecules can freely move about in a slithering pattern.

The density of molecules in a gas is often lower than that of the same chemical composition in a liquid or solid, and they move even more freely than in a liquid. The speed of molecular motion increases as the absolute temperature rises for a certain molecule in a given state (solid, liquid, or gas).

In biology

What is a molecule in biology
What is a molecule in biology

A substance is composed of the smallest particles with all of the physical and chemical characteristics of that substance. One or more atoms make up each molecule. 

If they contain more than one atom, it can either be the same atom (the oxygen molecule contains two oxygen atoms) or a different atom (the water molecule contains two hydrogen atoms and one oxygen atom). It is common for biological molecules such as proteins and DNA to contain hundreds of thousands of atoms.

Protein molecules, for example, can contain hundreds or even thousands of atoms that may be connected in long chains. The molecules can sometimes behave strangely in liquids containing them. Even after the flask has been restored to its upright position, a liquid may flow from a flask from which some of it has been poured.  

In chemistry 

A substance consisting of the smallest particles that possess all of its physical and chemical properties. Atoms are the basic building blocks of molecules.

Molecular molecules have an equal positive and negative charge if they are electrically neutral. This molecule experiences forces according to how its positive and negative charges are arranged and distributed in space.

If the arrangement of the molecules is spherically symmetric, the molecule is considered nonpolar. In the setting of an electric or magnetic field, a molecule has a dipole moment, in which the amount of excess positive charge on one end of the molecule is greater than the amount of excess negative charge on the other.

To indicate its polarity, the excess positive charge on one end is greater than the amount of negative charge on the other end. The molecules tend to gravitate towards orientations that produce attractive forces when they have the freedom to rotate.

Polar substances (water-loving) are hydrophilic (love water) while nonpolar compounds (lipid-lovers) are lipophilic (like lipids). Consequently, lipid-soluble, nonpolar compounds flow freely across cell membranes since they dissolve in the hydrophobic, nonpolar component of the lipid bilayer.

In a cell membrane, nonpolar lipid bilayers allow water (a polar molecule) to pass through, but many other polar molecules are impermeable, such as charged ions or molecules with many polar side chains. Lipid membranes are capable of allowing polar compounds to travel via specific transport methods.

Molecules can be formed from any combination of atoms with a predetermined ratio; for example, every water molecule has two hydrogen atoms and one oxygen atom. The property of chemical compounds makes them different from solutions and other mechanical mixes.

In mechanical combinations, hydrogen and oxygen may be present in any arbitrary ratios, but when they are ignited, these ingredients will only combine according to specific proportions to produce water (H2O).

A molecule can be formed by pairing the same type of atoms in distinct but equally proportional ways; for example, two hydrogen atoms, together with one oxygen atom, yield a water molecule, whereas two hydrogen atoms, together with two oxygen atoms, yield a hydrogen peroxide molecule (H2O2). In addition, atoms can bind together in identical amounts to create different molecules.

A molecule is an isomer when its atoms are arranged differently within the molecule. For example, a methyl ether (CH3OCH3) and an ethanol (CH3CH2OH) contain the same amount of oxygen, carbon, and hydrogen as well as the same number of hydrogen atoms. However, their atoms are connected in different ways.

Compounds do not all consist of the same molecular unit. For example, Sodium chloride (ordinary table salt) is composed of sodium ions and chlorine ions arranged in a lattice structure, each sodium ion surrounded by six orthogonal chlorine ions and each orthogonal sodium ion by six orthogonal sodium ions.

An Ion of sodium or chlorine close by exerts the same forces as any ion of sodium. The aggregation cannot be recognized as sodium chloride because there is no distinct aggregation. As a result, sodium chloride and other substances of a similar nature do not have the concept of a chemical molecule. Thus, the formula for such a compound is written based on the atoms’ simplest ratio, sometimes referred to as a formula unit – in this case, sodium chloride, NaCl.

Molecules are bound by covalent bonds, which are shared electron pairs. Bonds with a directed structure have atoms oriented in a specific way relative to one another to increase their strength.

Thus, each molecule’s structure is defined and relatively rigid because its atoms are arranged in a fixed way. Known as valence in structural chemistry, this concept describes how atoms combine in specific ratios and how this impacts bond lengths and directions.

Molecule properties are tied to their structures; for example, water molecules have dipole moments due to structural bentness, whereas carbon dioxide molecules are linear and lack dipole moments.

In science 

The meaning of scientific terms often comes from their use rather than their definition, as with the meaning of everyday words. In describing species and power, imprecision is not an issue. The same may be said for describing molecules.

A chemical compound can consist of no more than two or more atoms bound together by a chemical bond, for example, which has been defined as the simplest unit of a compound.

A particle is a collection of two or more atoms that is composed of the chemical and physical properties of the substance. According to another definition, it is a collection of atoms that are chemically bound together.

In contrast, the second meaning, ‘the tiniest particle of a substance in which its qualities are preserved,’ is essentially meaningless. Describe the properties of the particles.

Since melting point and other bulk properties are the most significant attributes, we can conclude that the majority are bulk attributes. It is also noteworthy that the notion that molecules are composed of two or more atoms linked together by chemical bonds raises thorny questions about the definition of bonds (including van der Waals forces and mechanical bonds) and the distinction between molecules and ionic crystals (as Gilbert Lewis did a century ago).

According to Nature Chemistry’s editor Stuart Cantrill, catenanes and rotaxanes, which are composed of covalently linked assemblies mechanically linked together (threaded rings, for example), must be classified as molecules, not supramolecular. Chemists from other colleges added their viewpoints, causing a (good-natured) Twitterstorm.


Divide a sample of a substance into progressively smaller parts and you will not change its chemical properties or composition until portions consisting of single molecules are reached.

Subsequent subdivisions of a substance typically result in smaller portions with different chemical characteristics and compositions from the original. When the atoms in the molecule are fragmented, the chemical bonds that hold them together are broken.

During the formation of an atom, a single positive-charged nucleus is surrounded by a disc of negatively charged electrons. When atoms are in close proximity to one another, electron clouds interact between them and with the nuclei.

The atoms become linked together to form molecules when the energy of the system is decreased by this interaction. Molecules, from a structural point of view, consist of an arrangement of atoms held together by valence forces.

Two atoms are bonded together to form a diatomic molecule. Diatomic molecules have homonuclear constructions, such as oxygen molecules (O2), while heteronuclear diatomic molecules have two atoms distinct from one another, such as carbon monoxide molecules (CO). Molecules with more than two atoms (H2O) are polyatomic molecules like carbon dioxide (CO2) and water. In polymer molecules there are often a great deal of component atoms.


There are simple molecules and complex molecules. Listed below are examples of common molecules:

Water (H2O)

Nitrogen (N2)

Ozone (O3)

Calcium oxide (CaO)

Glucose (C6H12O6)

Table salt (NaCl)

Read also: What is Microbiology? Definition,Meaning ; Biochemistry Meaning and Uses; Importance of Microbiology in Medicine

External resources: Britannica

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