Covalent Bond: Compact Notes for Quick Review

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A covalent bond is a chemical bond formed when two or more atoms share electrons to create stable electron pairs, typically between non-metal atoms, to achieve a full outer electron shell.

In the world of chemistry, atoms combine to form different substances. They do this by forming chemical bonds. One important type of chemical bond is the covalent bond. This bond plays a crucial role in forming molecules like water, oxygen, and carbon dioxide, which are essential for life.

In this blog, we will explore covalent bonds in a simple and easy-to-understand manner. If you’re preparing for exams like SSC, RRB NTPC, UPSC, or state-level exams, this guide will help you understand the concept thoroughly.

What is a Covalent Bond?

A covalent bond is a type of chemical bond where two or more atoms share electrons to achieve stability. Unlike ionic bonds, where electrons are transferred, covalent bonds involve the sharing of electrons.

Key Points

  • A covalent bond is formed between non-metal atoms.
  • A covalent bond is a bond where two atoms share electrons to complete their outermost shell.
  • Atoms usually aim for stability (Octet Rule – having 8 electrons in the outer shell).
  • When atoms cannot transfer electrons (like in ionic bonds), they share them, leading to covalent bonding.
  • The resulting combination of atoms is called a molecule.

Examples

  • Water (H₂O): Here, oxygen (O) shares electrons with hydrogen (H) atoms to form a stable water molecule.
  • In O₂ (Oxygen molecule), each oxygen atom shares two electrons, forming a double covalent bond.
🔍 Did You Know?

✔️ The strongest covalent bond in nature is the triple bond in nitrogen (N₂)!

✔️ Diamonds are made entirely of carbon atoms held together by covalent bonds! 💎

✔️ Graphite (used in pencils) is made of covalent bonds of carbon atoms.

Why Do Atoms Form Covalent Bonds?

Atoms always try to achieve stability by completing their outermost electron shell (also called the valence shell). This is known as the Octet Rule, which states that atoms tend to have eight electrons in their outer shell to become stable.

Ways to Achieve Stability

  1. By transferring electrons → Forms Ionic Bonds (e.g., NaCl – Table Salt)
  2. By sharing electrons → Forms Covalent Bonds (e.g., H₂O – Water)

Types of Covalent Bonds

Covalent bonds can be classified based on how many electron pairs are shared.

1. Single Covalent Bond

  • One pair of electrons (2 electrons) is shared.
  • Example: Hydrogen (H₂)

2. Double Covalent Bond

  • Two pairs of electrons (4 electrons) are shared.
  • Example: Oxygen (O₂)

3. Triple Covalent Bond

  • Three pairs of electrons (6 electrons) are shared.
  • Example: Nitrogen (N₂)
Type of BondNumber of Electron Pairs SharedExample
Single Bond1 pair (2 electrons)H₂, Cl₂
Double Bond2 pairs (4 electrons)O₂, CO₂
Triple Bond3 pairs (6 electrons)N₂, C₂H₂
🔍 Did You Know?

✔️ The air you breathe (O₂ and N₂) is held together by covalent bonds.

✔️ DNA molecules in your body are held by covalent bonds.

Examples of Covalent Bond in Daily Life

Covalent bonds are present in many common substances that we use daily:

CompoundMolecular FormulaUses
WaterH₂OEssential for life
OxygenO₂Required for breathing
Carbon DioxideCO₂Used by plants for photosynthesis
MethaneCH₄Main component of natural gas

Difference Between Covalent and Ionic Bonds

FeatureCovalent BondIonic Bond
FormationSharing of electronsTransfer of electrons
Types of AtomsBetween non-metalsBetween metals & non-metals
ExampleH₂O (Water)NaCl (Salt)
Bond StrengthGenerally weakerGenerally stronger

Properties of Covalent Compounds

PropertyCovalent Compounds
StateMostly gases & liquids, some solids
Melting/Boiling PointGenerally low
SolubilityInsoluble in water, soluble in organic solvents
ConductionPoor conductors of electricity

Key Takeaways for Exam Preparation

  • Covalent bonds involve the sharing of electrons.
  • They occur between non-metal atoms.
  • There are three types: Single, Double, and Triple bonds.
  • Covalent compounds are found in essential substances like water, oxygen, and carbon dioxide.
  • Understanding covalent bonds helps in chemistry, biology, and even environmental science.

Sample MCQs (with Answers)

Q1. A covalent bond is formed by:
(a) Transfer of electrons
(b) Sharing of electrons
(c) Attraction between ions
(d) None of these
Answer: (b) Sharing of electrons

Q2. Which of the following has a double covalent bond?
(a) H₂
(b) O₂
(c) N₂
(d) HCl
Answer: (b) O₂

Q3. Graphite is a good conductor of electricity because:
(a) It has free ions
(b) It has free electrons
(c) It is metallic
(d) It is ionic
Answer: (b) It has free electrons

Q4. Which of the following is a polar covalent compound?
(a) H₂
(b) O₂
(c) H₂O
(d) Cl₂
Answer: (c) H₂O

Q5. N₂ molecule has how many covalent bonds?
(a) 1
(b) 2
(c) 3
(d) 4
Answer: (c) 3

Important FAQs

Q1. Who introduced the concept of covalent bond?
Ans: Gilbert N. Lewis in 1916.

Q2. Which is stronger: ionic or covalent bond?
Ans: Both depend on conditions, but covalent bonds are very strong in molecules like diamond.

Q3. What is the simplest covalent molecule?
Ans: Hydrogen molecule (H₂).

Q4. Why are covalent compounds poor conductors?
Ans: They lack free ions or electrons.

Q5. Can a molecule have both ionic and covalent bonds?
Ans: Yes, e.g., NaOH has both.

Q6. What rule explains covalent bonding?
Ans: Octet Rule (atoms try to complete 8 electrons).

Q7. Which covalent compound is essential for respiration?
Ans: Oxygen (O₂).

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