What are Diatomic Molecules? (2023)

Table of Contents (click to enlarge)
  • molecules
  • diatomic molecules
  • Types of Diatomic Molecules
  • Finally

Diatomic molecules are molecules with two atoms in their structure. They can be two atoms attached to a nucleus or two atoms attached to more than one nucleus (heteronuclear).

The world of the very small dictates the qualities exhibited by the world of the very large. This "little world" is inhabited by atomic and subatomic particles.

Atoms can be thought of as Lego pieces; They are combined in different ways to do different things. So the same Lego bricks can build a boat or a bridge as atoms can build a blade of grass or a giraffe.

What are Diatomic Molecules? (1)

Atoms combine to form molecules. (Image credit: Vitalii Barida/Shutterstock)

When two or more atoms join together, they form a molecule. The number of atoms in a molecule denotes the prefix, therefore a molecule containing two atoms is said to be diatomic.

There are different types of diatomic molecules. Let's start this discussion with a better understanding of how a molecule works.

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Molecules are the constituents of matter; They are the smallest particles that exhibit the chemical properties of the element to which they belong. Molecules can be homonuclear, meaning they can be made up of atoms of only one chemical element (for example, hydrogen (H2)), or they can be heteronuclear, meaning they can be a chemical compound with atoms of more than one element (for example, water (H2Ö)).

Molecules are formed when two or more atoms are held together by chemical bonds. This bond represents a permanent attraction between molecules, ions and atoms. This bond can be the result of the attraction of oppositely charged ions or the sharing of electrons between two atoms.

Atoms are stable when their outer shell is full or empty. To be considered full, it must have 8 electrons in the outer shell called the octet. When this is not the case, atoms combine to gain or lose an electron from another atom or share pairs of electrons with another atom.

This transaction of electrons gives way to chemical bonds:

ionic compound

This bond occurs when electrons are completely transferred from one atom to another. This creates two ions, the atoms that have gained one or more electrons are called anions (negatively charged) and those that have lost one or more electrons are called cations (positively charged).

(Video) What are "diatomic" molecules?

What are Diatomic Molecules? (2)

How ionic bonding works in NaCl. (Image credit: VectorMine/Shutterstock)

Take the case of NaCl (table salt). Chlorine contains 7 electrons in its outer shell and needs one to complete its octet. Sodium has 1 electron in its outer shell, which it donates to chlorine to form an ionic bond.

Covalent bond

A covalent bond occurs when two atoms share pairs of electrons; it is also the strongest of chemical bonds. This exchange of electrons helps the atoms reach their stable state.

There are two main types of covalent bonds: nonpolar and polar covalent bonds. Nonpolar or purely covalent bonds are formed between atoms that have the same electronegativity and therefore share electrons equally. This is observed for atoms with an electronegativity difference of less than 0.4.

What are Diatomic Molecules? (3)

Polar and nonpolar covalent bonds. (Image credit: udaix/Shutterstock)

When the electronegativity difference is between 0.4 and 1.7, the bond becomes polar. In this case, the electrons spend more time, on average, in the atom with the higher electronegativity. For example, in water (H2O), on average, electrons are associated with oxygen (O) most of the time, giving it a partial negative charge and hydrogen (H) a partial positive charge.

diatomic molecules

Molecules with two atoms of the same or different chemical elements are called diatomic. Almost all diatomic elements are gases (eg, hydrogen, nitrogen) at room temperature. Some elements become diatomic at higher temperatures.

Diatomic molecules of nitrogen (78%) and oxygen (21%) make up the majority of Earth's atmosphere. At an interstellar level, the diatomic molecule of hydrogen is the most abundant in the entire universe.

Types of Diatomic Molecules

Diatomic molecules can be two atoms sharing a nucleus, usually composed of the same element, or two atoms in two nuclei of two different elements.

Homonuclear Diatomic Molecules

What are Diatomic Molecules? (4)

Homonuclear diatomic molecules. (Image credit: OSweetNature/Shutterstock)

Also read:What is the difference between a molecule and a compound?

(Video) Diatomic Elements & Molecules

Homonuclear molecules consist of atoms of a single element. The only elements that form diatomic molecules at room temperature are gases. These are:

Hydrogen – H2

Hydrogen is abundant throughout the universe. A hydrogen atom consists of a single valence electron in its outer shell. To become stable, the hydrogen atom needs one more electron to complete its shell. It does this by sharing a proton with another hydrogen atom through a nonpolar covalent bond, making it a diatomic molecule.

What are Diatomic Molecules? (5)

hydrogen molecule. (Image credit: ch123/Shutterstock)

Nitrogen – N2

Nitrogen is the most prominent element in Earth's atmosphere. A nitrogen atom consists of 5 valence electrons in its outermost shell. To create a stable compound, two nitrogen atoms bond together and share three electrons from the opposite atom, leaving 8 electrons in the bottom shell. This becomes a diatomic nitrogen molecule with nonpolar covalent bonds between the two atoms.

What are Diatomic Molecules? (6)

nitrogen molecule. (Image credit: Orange Deer Studio/Shutterstock)


Oxygen is readily found in Earth's atmosphere, as well as in the general composition of the universe. An oxygen atom consists of 6 valence electrons in its outermost shell. It shares two electrons with another oxygen atom through a nonpolar covalent bond to become a stable diatomic molecule.

What are Diatomic Molecules? (7)

oxygen molecule (Image credit: Orange Deer Studio/Shutterstock)

Flúor – F2

Fluorine is a highly toxic glowing gas with a pungent odor that exists as a diatomic molecule at room temperature. The outermost shell of a fluorine atom contains 7 valence electrons. It shares an electron with another fluorine atom through a nonpolar covalent bond to become stable and form a diatomic fluorine molecule.

What are Diatomic Molecules? (8)

fluorine molecule. (Image credit: Orange Deer Studio/Shutterstock)

(Video) What are the Diatomic Elements?

Cloro – Cl2

Chlorine is a highly reactive element that is greenish-yellow in color and exists as a gas at room temperature. It consists of 3 electron shells and has 7 electrons in its outermost shell. It shares an electron with another chlorine atom through a nonpolar covalent bond to form a stable diatomic chlorine molecule.


At room temperature, bromine is a reddish-brown liquid. When the temperature increases, this element forms diatomic molecules and becomes a gas. The outermost shell consists of 7 electrons and needs one to stabilize and form Br.2.

iodine - I2

At room temperature, iodine exists as a purple-black, nonmetallic solid. Similar to bromine, forms a diatomic I2molecule when heated. An iodine atom shares an electron with another atom to complete its octet and become stable.

Heteronuclear Diatomic Molecules

Atoms that combine with atoms of other elements to become stable and form diatomic molecules are heteronuclear. Many elements can combine to form these heteronuclear diatomic molecules under favorable conditions.

Some examples are:

Clorwasserstoff – HCL

This is a colorless gas at room temperature and forms white fumes (hydrochloric acid) on contact with the atmosphere. A hydrogen atom has one electron in its outermost shell and chlorine has 7, so they form a covalent bond to complete the octet and become a stable diatomic molecule.

What are Diatomic Molecules? (9)

Diatomic LCH (Image credit: Peter Hermes Furian/Shutterstock)

Carbon Monoxide - CO

Carbon monoxide is a flammable gas that is odorless, colorless, and tasteless. It is slightly less dense than air. Carbon has 4 and oxygen has 6 valence electrons in the outermost shell. Atoms form a triple bond to become stable, thus becoming a heteronuclear diatomic molecule.

What are Diatomic Molecules? (10)

diatomic carbon monoxide. (Image credit: ch123/Shutterstock)

Nitric Oxide - NO

Nitrous oxide is a colorless gas. A nitrogen atom has 5 valence electrons in the outermost shell and oxygen has 6, so they combine to form stable diatomic molecules. One electron is left unpaired, making nitric oxide a free radical.

Also read:What is the octet rule?

What are Diatomic Molecules? (11)

(Video) Super Common Mistake: Diatomic Elements

Nitric oxide with a free radical. (Image credit: molekuul_be/Shutterstock) (Image credit: molekuul_be/Shutterstock)


Some of the most abundant and common elements on our planet are diatomic molecules. Diatomic molecules, ranging from the homonuclear to the heteronuclear categories, represent a stable state for elements due to the strong chemical bonds that form between valence electrons.

References (click to enlarge)
  1. What are molecules? | ask Dr. Universe | Washington State .... Washington State University
  2. The Covalent Bond - people.seas.harvard.edu:80
  3. http://web.archive.org/web/20191201164935/http://academic.brooklyn.cuny.edu:80/biology/bio4fv/page/polar_c.htm
  4. Bond in simple diatomic molecules. The University of Illinois Urbana-Champaign
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What is diatomic molecule Short answer? ›

diatomic molecule, any chemical compound that is made up of only two atoms. The two atoms can be the same type of atom, such as oxygen (O2), where both atoms in the molecule are oxygen atoms; such molecules are known as homonuclear diatomic molecules.

Which are the diatomic molecules? ›

Eight Diatomic Elements:
  • Hydrogen.
  • Nitrogen.
  • Oxygen.
  • Fluorine.
  • Chlorine.
  • Bromine.
  • Iodine.

What is a diatomic molecule quizlet? ›

Diatomic element definition. Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements.

What is a diatomic molecule Quizizz? ›

Diatomic elements are defined as IDENTICAL elements that bond with each other (i.e. Oxygen with Oxygen).

What is a diatomic element simple definition? ›

A diatomic element is a molecule composed of two of the same atom. The word diatomic comes from 'di' meaning two, and 'atomic' meaning atom. A monatomic element is stable with just one atom. These diatomic elements are most stable in this paired form because it allows them to follow the octet rule.

What is diatomic example? ›

Hydrogen , Nitrogen , and Oxygen are examples of diatomic molecules.

What is diatomic molecule give two examples? ›

Most of the gases in the atmosphere are diatomic molecules. If the molecule consists of two same atoms, then it is termed as homonuclear. Example: Oxygen gas (O2) , hydrogen gas (H2) , nitrogen gas (N2) , etc.

Why do diatomic molecules form? ›

If the two atoms are the same, for example, hydrogen, it is called a homonuclear diatomic molecule. Hydrogen has one electron less than stable inert gas configuration. So, it shares that electron with another hydrogen atom and forms a diatomic molecule which is stable.

What gases are diatomic molecules? ›

Except for hydrogen, the elements that occur naturally as gases are on the right side of the periodic table. Of these, all the noble gases (group 18) are monatomic gases, whereas the other gaseous elements are diatomic molecules (H2, N2, O2, F2, and Cl2).

Why is it called diatomic? ›

A molecule made up of two of the same atoms is called a diatomic element. Diatomic is derived from the words 'di' for two and 'atomic' for atom. With only one atom, a mono-atomic element is stable. The term “homonuclear diatomic molecules” is used to describe diatomic elements.

What are diatomic elements called? ›

The diatomic elements are also called homonuclear molecules, which means that the molecule is made up of all the same type of atom. Nitrogen will always be found as N2 , because there are two nitrogen atoms bonded covalently together. The same goes for H2 , O2 , F2 , Cl2 C l 2 , Br2 B r 2 , and I2 .

What is the best definition for molecule? ›

A molecule is two or more atoms connected by chemical bonds, which form the smallest unit of a substance that retains the composition and properties of that substance. Molecules form the basis of chemistry. Molecules are noted with the element symbol and a subscript with the number of atoms.

What are the 7 diatomic molecules? ›

So these are our seven diatomic elements: Hydrogen, Nitrogen, Flourine, Oxygen, Iodine, Chlorine, Iodine, and Bromine.

Which is not a diatomic molecule? ›

Carbon does not exist as a diatomic molecule. The seven elements that do are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and...

What is a diatomic molecule kid definition? ›

Kids Encyclopedia Facts. Diatomic molecules are molecules made only of two atoms, of either the same or different chemical elements. Two atoms are bonded together to form a unit known as a diatomic molecule. Examples are hydrogen (H2), nitrogen (N2) and oxygen (O2), and carbon monoxide (CO).

How do diatomic molecules form bonds? ›

Bonding in Diatomic Molecules

In homonuclear diatomic molecules, the bonding is covalent. Each atom in the molecule has equal electronegativity; electrons are shared equally between the two atoms. In heteronuclear diatomic molecules, the atoms differ in electronegativity; these molecules have polar covalent bonds.

Are all diatomic molecules elements? ›

Diatomic elements are pure elements that form molecules consisting of two atoms bonded together. There are seven diatomic elements: hydrogen, nitrogen, oxygen, fluorine, chlorine, iodine, bromine. These elements can exist in pure form in other arrangements.

What is a diatomic gas quizlet? ›

What is a diatomic molecule? molecules composed of only two atoms. Which elements occurs naturally as a diatomic molecule? hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine.

Why are there only 7 diatomic elements? ›

They are generally too reactive to be left by themselves. There are only seven of them: hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. The diatomic elements are also called homonuclear molecules, which means that the molecule is made up of all the same type of atom.

Are all Group 7 diatomic? ›

The group 7 elements exist as diatomic molecules . Their chemical formulae are F 2, Cl 2, Br 2 and I 2. The bond between the atoms in a molecule is very strong, but the forces of attraction between molecules are weak. This explains why group 7 elements have low boiling points.


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