Lewis structures for molecules having multiple covalent bonds are an essential part of Class 11 Chemistry, helping students understand how atoms share more than one pair of electrons to form double and triple bonds. These exam-oriented notes by chief author Neeraj Anand of Anand Classes explain the Lewis structures of molecules with multiple covalent bonds through simple illustrations, step-by-step methods, and clear concepts. Specially prepared for CBSE, JEE Main, JEE Advanced, and NEET aspirants, these study materials strengthen conceptual understanding and improve problem-solving skills for board and competitive examinations.
Lewis structures for molecules having multiple covalent bonds
If the normal valence of an atom is not satisfied by sharing single electron pair
between atoms, the atoms may share more than one electron pair between them.
(i) If two atoms share one electron pair, bond is known as single covalent bond and is represented by one dash (—).
(ii) If two atoms share two electron pairs, bond is known as double covalent bond and is represented by two dashes (=).
(iii) If two atoms share three electron pairs, bond is known as triple covalent bond and is represented by three dashes (.
Let us discuss some examples of molecules having double and triple bonds.
Important concepts connected to this topic are Covalent Bond, Formation of Hydrogen (H₂), Chlorine (Cl₂), Hydrogen Chloride (HCl), Water (H₂O), Ammonia (NH₃) Molecules
How does an Oxygen (O₂) Molecule form double covalent bond between two Oxygen atoms ?
An oxygen molecule (O₂) is formed when two oxygen atoms share two pairs of electrons. This type of bond is called a double covalent bond.
Each oxygen atom has the electronic configuration 2, 6, which means it has six electrons in its outermost (valence) shell. To achieve a stable octet (eight electrons in the valence shell), each oxygen atom requires two more electrons.
When two oxygen atoms come close to each other, each oxygen atom contributes two of its valence electrons for sharing. These four electrons form two shared pairs of electrons between the two oxygen atoms.
As a result:
- Each oxygen atom shares two electrons and receives two electrons from the other oxygen atom.
- Both oxygen atoms attain a stable octet electronic configuration.
Therefore, an oxygen (O₂) molecule is formed by the mutual sharing of two pairs of electrons, resulting in a double covalent bond (O=O) between the two oxygen atoms. Each oxygen atom also has two lone pairs of electrons that are not involved in bonding. Since both atoms are identical and have the same electronegativity, the shared electron pairs are attracted equally by both atoms. Hence, the O=O bond is a non-polar covalent bond. Here the two shared pairs of electrons ( :: ) or the double line (=) represent the double covalent bond between the two oxygen atoms.
Strengthen your fundamentals with Lattice Enthalpy of Ionic Crystals, Properties of Ionic Compounds
How does a Carbon Dioxide (CO₂) Molecule form double covalent bond between the carbon atom and an oxygen atom ?
A carbon dioxide (CO₂) molecule is formed when one carbon atom shares two pairs of electrons with each of two oxygen atoms. This results in the formation of two double covalent bonds.
A carbon atom has the electronic configuration 2, 4, which means it has four electrons in its outermost (valence) shell. To attain a stable octet, carbon requires four more electrons.
Each oxygen atom has the electronic configuration 2, 6, which means it has six electrons in its outermost (valence) shell. Each oxygen atom requires two more electrons to complete its octet.
When the atoms combine, the carbon atom shares two of its valence electrons with one oxygen atom and two with the other oxygen atom. At the same time, each oxygen atom shares two of its valence electrons with the carbon atom. Thus, two pairs of electrons are shared between carbon and each oxygen atom, forming two double covalent bonds.
As a result:
- The carbon atom attains a stable octet by sharing four pairs of electrons.
- Each oxygen atom also attains a stable octet by sharing two pairs of electrons with carbon.
Therefore, a carbon dioxide (CO₂) molecule is formed by the mutual sharing of electrons, resulting in two double covalent bonds (O=C=O). Each oxygen atom has two lone pairs of electrons, while the carbon atom has no lone pairs. Although each C=O bond is polar covalent, the molecule has a linear and symmetrical shape, so the bond polarities cancel each other. As a result, carbon dioxide is a non-polar molecule. Here each double line (=) or two shared pairs of electrons (::) represents a double covalent bond between the carbon atom and an oxygen atom.
Gain deeper understanding by studying Ionic or Electrovalent Bond Explanation, Examples, Factors Affecting Formation of Ionic Bonds
How does a Nitrogen (N₂) Molecule form triple covalent bond between two Nitrogen atoms ?
A nitrogen molecule (N₂) is formed when two nitrogen atoms share three pairs of electrons. This type of bond is called a triple covalent bond.
Each nitrogen atom has the electronic configuration 2, 5, which means it has five electrons in its outermost (valence) shell. To achieve a stable octet (eight electrons in the valence shell), each nitrogen atom requires three more electrons.
When two nitrogen atoms come close to each other, each nitrogen atom contributes three of its valence electrons for sharing. These six electrons form three shared pairs of electrons between the two nitrogen atoms.
As a result:
- Each nitrogen atom shares three electrons and receives three electrons from the other nitrogen atom.
- Both nitrogen atoms attain a stable octet electronic configuration.
Therefore, a nitrogen (N₂) molecule is formed by the mutual sharing of three pairs of electrons, resulting in a triple covalent bond (N≡N) between the two nitrogen atoms. Each nitrogen atom also has one lone pair of electrons that is not involved in bonding. Since both atoms are identical and have the same electronegativity, the shared electron pairs are attracted equally by both atoms. Hence, the N≡N bond is a non-polar covalent bond. Here the three shared pairs of electrons (≡) represent the triple covalent bond between the two nitrogen atoms, and the colon (:) on each side represents the one lone pair of electrons present on each nitrogen atom.
Frequently linked concepts include Lewis Electron Dot (Symbols) Structure Theory and its Significance
How does a Ethylene (C₂H₄) Molecule form ? Why double covalent bond exists between the two carbon atoms ?
An ethylene (C₂H₄) molecule is formed when two carbon atoms share two pairs of electrons with each other and each carbon atom shares one pair of electrons with two hydrogen atoms.
Each carbon atom has the electronic configuration 2, 4, which means it has four electrons in its outermost (valence) shell. To attain a stable octet, each carbon atom requires four more electrons.
Each hydrogen atom has one electron in its only shell and requires one more electron to attain the stable duplet configuration of helium.
In the ethylene molecule:
- Each carbon atom shares one of its valence electrons with each of two hydrogen atoms, forming two single covalent bonds (C–H).
- The remaining two valence electrons of each carbon atom are shared with the other carbon atom, forming two shared pairs of electrons. This results in a double covalent bond (C=C) between the two carbon atoms.
As a result:
- Each carbon atom attains a stable octet by forming two single bonds with hydrogen atoms and one double bond with the other carbon atom.
- Each hydrogen atom attains a stable duplet configuration by sharing one pair of electrons with a carbon atom.
Therefore, an ethylene (C₂H₄) molecule is formed with one double covalent bond between the two carbon atoms and four single covalent bonds between carbon and hydrogen atoms.
The C=C double bond consists of two shared pairs of electrons, while each C–H bond consists of one shared pair of electrons. Although each C–H bond is nearly non-polar, the double bond between the carbon atoms is the characteristic feature of ethylene, making it an unsaturated hydrocarbon (alkene).
Enhance your preparation with What are the differences between electron gain enthalpy and ionization enthalpy?
How does an Acetylene (C₂H₂) Molecule form ? Why triple covalent bond exists between the two carbon atoms ?
An acetylene (C₂H₂) molecule is formed when two carbon atoms share three pairs of electrons with each other and each carbon atom shares one pair of electrons with one hydrogen atom.
Each carbon atom has the electronic configuration 2, 4, which means it has four electrons in its outermost (valence) shell. To attain a stable octet, each carbon atom requires four more electrons.
Each hydrogen atom has one electron in its only shell and requires one more electron to attain the stable duplet configuration of helium.
In the acetylene molecule:
- Each carbon atom shares one of its valence electrons with one hydrogen atom, forming one single covalent bond (C–H).
- The remaining three valence electrons of each carbon atom are shared with the other carbon atom, forming three shared pairs of electrons. This results in a triple covalent bond (C≡C) between the two carbon atoms.
As a result:
- Each carbon atom attains a stable octet by forming one single bond with a hydrogen atom and one triple bond with the other carbon atom.
- Each hydrogen atom attains a stable duplet configuration by sharing one pair of electrons with a carbon atom.
Therefore, an acetylene (C₂H₂) molecule is formed with one triple covalent bond between the two carbon atoms and two single covalent bonds between carbon and hydrogen atoms.
The C≡C triple bond consists of three shared pairs of electrons, while each C–H bond consists of one shared pair of electrons. The triple bond is stronger and shorter than a double or single carbon–carbon bond. Acetylene is an unsaturated hydrocarbon (alkyne) because it contains a carbon–carbon triple bond.
Master related concepts such as Ionization Enthalpy Trends Along a Period and Down a Group
Important Classification of Elements and Periodicity in Properties Chapter Interlinks
This section provides a complete and interconnected study of Classification of Elements and Periodicity in Properties, starting with detailed theory and notes for Class 11 Chemistry to build a strong conceptual foundation. You can explore atomic radius and its types including covalent, van der Waals, metallic, and ionic radii to understand periodic trends in atomic size. It also includes Screening Effect (Shielding Effect) : Calculation of Effective or Reduced Nuclear Charge (Slater’s Rules), which explains how inner electrons reduce the nuclear attraction on outer electrons and influence periodic trends. In addition, topics like Radius of Cation is Less and Anion is More Than Its Parent Atom, Size Variation in Isoelectronic Series help explain how ionic size changes due to gain or loss of electrons and how nuclear charge affects size in species with the same number of electrons. The causes of periodicity explain why elements show repeating properties based on electronic configuration, which is further supported by the modern periodic law and structure of the modern periodic table including groups, periods, and blocks for elements even beyond atomic number 100. The historical development is covered through Mendeleev’s periodic law and table, leading to the modern classification of elements into s, p, d, and f blocks with prediction of period, group, and block. To strengthen exam preparation, you can practice JEE Main PYQs, IMU CET PYQs and Merchant Navy sponsorship exam MCQs, and other previous year questions with solutions, along with solved examples, conceptual questions, and practice problems on the modern periodic table. Learn more in this section also to radius of cation is less and anion is more than its parent atom and size variation in Isoelectronic Series. Additionally, complete study material, mock tests, and guidance are provided under Anand Classes Chemistry notes, along with expert support from Er Neeraj Anand, making this section a comprehensive resource for competitive exam preparation. This section also includes detailed study of What is Ionization Enthalpy? Definition, Units, Factors and Successive IE and Ionization Enthalpy Trends Along a Period and Down a Group for better understanding of periodic properties and reactivity of elements.