🧪 Microproject on Formation of Covalent Bond
Page 1 — Title Page
Title: Formation of Covalent Bond
Subject: Chemistry
Submitted by: [Your Name]
Class: [Your Class]
School/College: [Your Institute Name]
Submitted to: [Teacher’s Name]
Date: [Insert Date]
Aim:
To study in detail how covalent bonds are formed by electron sharing between atoms, the different types of covalent bonds, their characteristics, and their importance in the formation of compounds.
📘 Page 2 — Introduction
All substances around us are made of atoms and molecules. Atoms rarely exist alone; they combine with other atoms to achieve chemical stability.
Atoms achieve stability when their outermost shell (valence shell) becomes full — usually with 8 electrons (known as the octet rule).
There are two main ways atoms combine:
1. Ionic Bonding: Transfer of electrons (e.g., NaCl).
2. Covalent Bonding: Sharing of electrons (e.g., H₂, O₂, C₄).H
Covalent bonds mainly form between non-metallic elements that have similar electronegativities, so neither atom can fully remove electrons from the other. Instead, they share them.
⚛️ Page 3 — Definition and Basic Concept
A covalent bond is a chemical bond formed when two atoms share one or more pairs of electrons to achieve a stable noble gas configuration.
➡️ Example: Two hydrogen atoms each have one electron. By sharing their electrons, they form a single covalent bond (H–H), achieving the stable configuration of helium (2 electrons).
Each shared pair of electrons is represented by a dash (–) between atoms.
General Representation:
A : B → A–B
Here “:” represents shared electron pairs, and “–” shows the bond between atoms.
🔬 Page 4 — Conditions Necessary for Covalent Bond Formation
1. Atoms should have similar electronegativity:
The difference should be small so that neither atom can completely take the other’s electron.
2. Both atoms must need additional electrons to complete their octet.
3. Atoms must have high ionization energy:
They resist losing electrons, so they prefer sharing.
4. The bond must lead to a stable arrangement:
After sharing, both atoms should reach the nearest noble gas configuration.
5. Occurs mostly among non-metals such as H, O, N, Cl, C, S, etc.
📗 Page 5 — Types of Covalent Bonds
Depending on the number of shared electron pairs, there are three main types:
1. Single Covalent Bond (one pair shared):
Example – Hydrogen molecule (H₂), Chlorine molecule (Cl₂).
Representation: H–H, Cl–Cl.
→ Weakest but longest bond.
2. Double Covalent Bond (two pairs shared):
Example – Oxygen molecule (O₂), Carbon dioxide (CO₂).
Representation: O=O, O=C=O.
→ Stronger and shorter than single bond.
3. Triple Covalent Bond (three pairs shared):
Example – Nitrogen molecule (N₂), Acetylene (C₂H₂).
Representation: N≡N, HC≡CH.
→ Very strong and shortest bond.
⚗️ Page 6 — Formation of Hydrogen Molecule (H₂)
Each hydrogen atom has one electron.
When two H atoms come close, they share their single electrons to form a shared pair, resulting in both achieving a stable configuration like helium (2 electrons).
Electron Dot Structure: H : H → H–H
Explanation:
Each hydrogen atom contributes one electron.
The shared pair counts for both atoms.
The molecule formed is stable and neutral.
Bond type: Single covalent bond.
Bond energy: 436 kJ/mol.
🧬 Page 7 — Formation of Oxygen Molecule (O₂)
Each oxygen atom has 6 valence electrons and needs 2 more to complete its octet.
When two oxygen atoms share two pairs of electrons, each atom attains 8 electrons in its outermost shell.
Electron Dot Structure: O :: O → O=O
Explanation:
Two shared pairs mean a double bond.
Oxygen atoms are held together by strong attraction between shared electrons and nuclei.
Bond type: Double covalent bond.
Bond energy: 498 kJ/mol.
Result: Both atoms achieve stability like neon (2s²2p⁶).
⚛️ Page 8 — Formation of Nitrogen Molecule (N₂)
Each nitrogen atom has 5 valence electrons. To complete the octet, each needs 3 more electrons.
Hence, two nitrogen atoms share three pairs of electrons, forming a triple bond.
Electron Dot Structure: N ::: N → N≡N
Explanation:
Six electrons are shared between two atoms.
Triple bonds are very strong and give nitrogen gas great stability
This is why N₂ is very inert under normal conditions.
Bond type: Triple covalent bond.
Bond energy: 941 kJ/mol (very high).
📗 Page 9 — Polar and Non-Polar Covalent Bonds
1. Non-Polar Covalent Bond:
Formed when atoms share electrons equally.
Example: H₂, O₂, N₂, Cl₂, CH₄.
No partial charge develops.
2. Polar Covalent Bond:
Formed when atoms share electrons unequally due to electronegativity difference.
Example: HCl, H₂O, NH₃.
One atom becomes slightly negative (δ–), and the other slightly positive (δ+).
Example: In HCl, chlorine attracts the shared electron pair more strongly than hydrogen, creating partial charges: Hδ⁺ – Clδ⁻
🧾 Page 10 — Properties of Covalent Compounds
1. Usually gases or liquids; some are soft solids (e.g., wax).
2. Low melting and boiling points (weak intermolecular forces).
3. Do not conduct electricity – no free ions.
4. Insoluble in water, but soluble in organic solvents (benzene, ether).
5. Covalent bonds are directional in nature.
6. Bond strength: Triple > Double > Single.
7. Examples: H₂O, CH₄, NH₃, CO₂, N₂, Cl₂.
📘 Page 11 — Importance of Covalent Bonding
Responsible for the formation of essential life molecules (water, proteins, DNA).
Explains molecular geometry and shapes (VSEPR theory).
Determines physical properties like solubility and boiling point.
Plays a vital role in organic chemistry (C–C and C–H covalent bonds form the basis of life).
📚 Page 12 — Conclusion and References
Conclusion:
Covalent bonding occurs when atoms share electrons to achieve stability.
This sharing creates a strong bond that holds atoms together in molecules.
The type of covalent bond — single, double, or triple — depends on how many electron pairs are shared.
The concept of covalent bonding explains the existence and behavior of a wide range of molecular compounds, from simple gases like H₂ to complex organic molecules.
References:
1. NCERT Chemistry Textbook (Class 10 & 11)
2. Modern ABC Chemistry
3. Lakhmir Singh & Manjit Kaur – Chemistry
4. www.chemguide.co.uk
5. www.byjus.com
6. www.toppr.com
