Covalent Bond – Explanation, Examples, MCQs, Class 11 Chemistry Notes pdf download

Anand Classes presents detailed notes on the Covalent Bond for Class 11 Chemistry, covering its explanation, examples, MCQs, assertion-reason type questions, and case study-based problems. A covalent bond is formed by the mutual sharing of electrons between atoms to achieve stability. These notes provide a clear understanding of the concept with suitable examples, step-wise explanations, and exam-oriented practice questions. Specially designed according to NCERT syllabus for Class 11 students, JEE, and NEET aspirants, this study material comes in a simple and concise format. Click the print button to download study material and notes in PDF.

What is Covalent Bond ?

In 1919, Langmuir refined the Lewis postulations and introduced the term covalent bond.
According to the Lewis–Langmuir theory, atoms can combine by sharing of electrons between them.

Definition

The bond formed by mutual sharing of electrons between the combining atoms of the same or different elements is called a covalent bond.
Each atom contributes equal number of electrons for sharing to acquire the nearest noble gas configuration.
The compounds formed in this manner are called covalent compounds.

Formation of Hydrogen Molecule (H₂)

Let us consider the formation of a hydrogen molecule from two hydrogen atoms. When two hydrogen atoms approach each other:

• Each H atom has one electron.
• They share one electron each, forming a shared pair of electrons.
• This shared pair belongs simultaneously to both atoms, giving each the helium configuration (1s²).

Representation:
$$
\mathrm{H + H \;\longrightarrow\; H:H \;\text{or}\; H–H}
$$

Here, the shared electron pair is considered to belong to both hydrogen atoms.

The sharing of electrons can also be shown by drawing a circle around each atom. This also helps us to count the electrons around any atom; the shared electron pair is thought of as belonging exclusively to that atom.
For example, H₂ molecule is shown as :

Formation of Chlorine Molecule (Cl₂)

Similarly, two chlorine atoms combine with each other to form a molecule of chlorine.

• Each Cl atom has seven valence electrons ($[Ne]\,3s^2 3p^5$).
• Each atom needs one more electron to complete its octet.
• Both contribute one electron each, forming a single shared pair.
• Each Cl atom attains the argon configuration (octet).
• This results in the formation of a covalent bond in Cl2 molecule. This may be depicted as :

Representation:
$$
\mathrm{Cl + Cl \;\longrightarrow\; Cl:Cl \;\text{or}\; Cl–Cl}
$$

Formation of Hydrogen Chloride (HCl)

A covalent bond can also form between dissimilar atoms. For example, hydrogen and chlorine form a covalent bond between their atoms. In HCl molecule, hydrogen atoms has only one electron and chlorine atom has seven electrons in its valence shell. Therefore

• Hydrogen (1 electron) and Chlorine (7 electrons) mutual share one pair of electrons.
• Hydrogen attains the helium configuration, and chlorine attains the argon configuration (shown in above diagram)

Representation:
$$
\mathrm{H + Cl \;\longrightarrow\; H:Cl \;\text{or}\; H–Cl}
$$

Key Points

• Covalent bonds are formed by sharing (not transfer) of electrons.
• Each shared electron pair is counted as belonging to both atoms.
• Covalent bonding allows atoms to achieve noble gas configuration.
• The number of shared pairs determines whether the bond is single, double, or triple.

Short Answer Conceptual Types Questions (SAT) on Covalent Bond

Q1. What is a covalent bond?

A covalent bond is the bond formed by mutual sharing of electrons between two atoms so that each atom can achieve the nearest noble gas configuration.

Q2. How does a covalent bond differ from an ionic bond?

• Covalent bond: Involves sharing of electrons between atoms.
• Ionic bond: Involves transfer of electrons from one atom to another, forming oppositely charged ions.

Q3. Can covalent bonds form between different elements?

Yes. Example: HCl, where hydrogen and chlorine share one electron pair.

Q4. What is meant by single, double, and triple covalent bonds?

• Single bond: One shared electron pair (e.g., H$_2$, Cl$_2$).
• Double bond: Two shared electron pairs (e.g., O$_2$).
• Triple bond: Three shared electron pairs (e.g., N$_2$).

Multiple Choice Questions (MCQs) With Answers and Explanation on Covalent Bond

1. A covalent bond is formed due to:
A) Transfer of electrons
B) Sharing of electron pairs
C) Electrostatic attraction between ions
D) Movement of protons

Answer: B (Sharing of electron pairs)

2. Which of the following contains a double covalent bond?
A) H$_2$
B) O$_2$
C) N$_2$
D) Cl$_2$

Answer: B (O$_2$ has a double bond)

3. Which of the following is a covalent compound?
A) NaCl
B) MgO
C) HCl
D) KBr

Answer: C (HCl is formed by sharing of electrons)

Assertion Reason Type Questions With Answers and Explanation on Covalent Bond

Assertion (A): Hydrogen molecule (H₂) is formed by sharing of two electrons.
Reason (R): Each hydrogen atom requires one electron to achieve the helium configuration.

A) Both A and R are true, and R is the correct explanation of A
B) Both A and R are true, but R is not the correct explanation of A
C) A is true, R is false
D) A is false, R is true

Answer: A

Assertion (A): Chlorine molecule (Cl₂) is held together by a single covalent bond.
Reason (R): Each chlorine atom contributes two electrons to the bond.

A) Both A and R are true, and R is the correct explanation of A
B) Both A and R are true, but R is not the correct explanation of A
C) A is true, R is false
D) A is false, R is true

Answer: C (Each Cl atom contributes one electron, not two)

Case Study based on Covalent Bond

Passage:
Two hydrogen atoms combine to form a hydrogen molecule. Each hydrogen atom has one electron and needs one more to achieve helium configuration. They share a pair of electrons, forming a single covalent bond.

Questions:

1. How many electrons are shared in a hydrogen molecule?
2. What configuration does each hydrogen atom achieve after bond formation?
3. Why is the covalent bond in H$_2$ stable?

Answers:

1. Two electrons (one pair) are shared.
2. Each H atom achieves the helium (1s$^2$) configuration.
3. The shared electron pair lowers the potential energy, making the molecule more stable.