What are Diatomic molecules?

o Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements. The word ‘di’ is roused from Greek meaning ‘two.’

o Some element occurs in nature in the form of only one atom and are pretty stable, these are named as monoatomic molecules. ‘Mono’ which means single and ‘atomic’ means atom.

o For Instance: Neon (Ne), Argon (Ar), Helium (He) etc.

Types of Diatomic Molecules

Diatomic molecules are of two types;

Homonuclear Diatomic Molecules

o If diatomic molecule consists of only similar kind of element, then it is named as Homonuclear.

o For Instance: hydrogen (H2), oxygen (O2) etc.

Hetetronuclear Diatomic Molecules

o If diatomic molecule consists of two different kinds of elements, then it is named as Heteronuclear.

o For Instance: carbon monoxide (CO), nitric oxide (NO) etc.

Homonuclear Diatomic Molecules vs Heteronuclear Diatomic Molecules

Homonuclear Diatomic Molecules	Heteronuclear Diatomic Molecules
It consists of two similar atoms	It consists of two different kinds of atoms
Type of bonding present is covalent as each atom has similar electronegativity; so, electron is shared equally by both atoms.	Here the given atoms have different electronegativity; thus these shows polar covalent bonds. So, the molecules generally form Dipole.
For instance – H2, Cl2	For instance – NO, CO

o It should be noted that some diatomic molecules such as NaCl is strictly not just heteronuclear in nature because it does not show polar covalent bonding as NaCl is a product of ionization.

o At room temperature it exists in the form of crystal lattices. In this mentioned arrangement each ion is surrounded by six oppositely charged ions.

o However, in gaseous state NaCl shows diatomic phase with a polar covalent bond.

Occurrence of Diatomic Molecules

o There are numerous of diatomic molecules found in the Earth, and in interstellar space. Our earth atmosphere is composed of mostly two diatomic molecules: nitrogen (78%) and oxygen (21%) and hydrogen though is present only in parts per million in earth but it is the most abundant atom present in universe.

Structure of Diatomic Molecules

o All diatomic molecules are linear in structure and are largely characterized by the “bond length” or distance between two atoms.

o For instance- nitrogen has a triple bond, oxygen has a double bond and hydrogen, fluorine chlorine has single bond in their structure.

Diatomic Molecules List

o There are seven pure diatomic elements as given below;

o Hydrogen (H2)

o Nitrogen (N2)

o Oxygen (O2)

o Fluorine (F2)

o Chlorine (Cl2)

o Iodine (I2)

o Bromine (Br2)

There is a method to learn the above mentioned elements as Have No Fear of Ice Cold Beer

There are two another element, Astatine (atomic number 85) and Tennessine (atomic number 117) present in halogen group that may form diatomic molecules. Some scientists believe that tennessine behave like noble gases in nature and should thus remain in monoatomic form.

Diatomic Molecules Characteristic

Properties of some diatomic elements are given below;

i. Hydrogen (H2)

o Hydrogen is found generally in our universe. It has only one valence electron in its outer shell. It completes its outer shell by pairing with another hydrogen atom through a non-polar covalent bond.

o Uses of Hydrogen;

1. It is widely used in synthesis of vegetable oil.

2. Hydrogen is also used as fuel in rocket.

ii. Nitrogen (N2)

o Nitrogen has 5 electrons in its outer shell, thus to complete its octet it share three electron with another atom thus forming diatomic structure. Nitrogen forms triple bond.

o Uses of Nitrogen;

1. Nitrogen is largely used in preservation of food.

2. It is also used in manufacture of nitric acid, dyes, medicines and nylon.

iii. Fluorine (F2)

o It is a toxic gas with sharp smell. The outer most shell has seven electron thus become eight through sharing one electron with another fluorine atom.

o Uses of Fluorine;

1. It is extensively used as insulation of electric towers.

2. A compound of F2 is also widely used to etch glass.

iv. Chlorine (Cl2)

o It is a yellow-green reactive gas thus forming a diatomic molecule. It forms a single bond.

o Uses of Chlorine;

1. It is generally used as a disinfectant.

2. It is also used to make PVC.

v. Bromine (Br2)

o It is red brown liquid at room temperature. It usually changes into gas by increasing temperature.

o Uses of Bromine;

1. It is commonly used in manufacture of Methyl bromide which is a fumigant.

2. It is also used in making silver bromide, which is used in photographic emulsions.

vi. Iodine (I2)

o Iodine is a purple-black solid at room temperature. It also forms non polar single bond.

o Uses of Iodine;

1. It is an essential particle that helps in proper functioning of thyroid gland.

2. It is broadly used as an antiseptic.

vii. Hydrogen Chloride (HCl)

o This is a colorless gas and generally forms white fumes when comes in contact with atmosphere. Hydrogen has one electron in its outermost shell and Chlorine has seven so, both share one electron to complete their octet.

o Uses of HCl;

1. It is broadly used in production of many organic compound.

2. It is also used in purification of Table salt.

viii. Carbon Monoxide (CO)

o It is a flammable and odorless gas. Carbon has 4 and oxygen has 6 electron in outermost shell. The atoms form a triple bond thus becoming a heteromolecule.

o Uses of carbon monoxide

1. It is commonly used to remove rust from metals.

2. It is also used to acidify cola like beverages.

ix. Nitric Oxide (NO)

o It is a colorless gas. Nitrogen has 5 electrons whereas oxygen has 6 valence electrons, so they form a double bond and thus one electron is left unpaired.

o Uses of nitric oxide

1. It is widely used to relax the smooth muscle to dilate blood vessels.

Diatomic Molecules Citations

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Diatomic Molecules: Definition, List, Chart, and Examples