Chemical Bonding
Subject: Science (Chemistry) | Topic: Chemical Bonding
For TLT, ECT, PST, JEST & All Competitive Exams
In our last topic, we studied Atomic Structure and learned that electrons in the outermost shell — called valence electrons — determine how an atom reacts with other atoms. This is exactly what we explore now: Chemical Bonding, the process by which atoms join together to form molecules and compounds. This is a core, frequently tested topic in TLT, ECT, PST, and JEST exams.
What is a Chemical Bond?
A chemical bond is the force of attraction that holds two or more atoms together in a molecule or compound. Atoms form bonds because they want to achieve a stable electron arrangement, usually by having 8 electrons in their outermost shell — this is known as the Octet Rule (except hydrogen and helium, which are stable with 2 electrons).
Ionic Bond (Electrovalent Bond)
An Ionic Bond is formed when one atom transfers one or more electrons to another atom. The atom that loses electrons becomes a positively charged ion (cation), and the atom that gains electrons becomes a negatively charged ion (anion). These oppositely charged ions attract each other strongly, forming an ionic bond. Ionic bonds usually form between a metal and a non-metal.
Example: Sodium (Na) transfers one electron to Chlorine (Cl), forming Sodium Chloride (NaCl) — common table salt.
Ionic Bond Formation (NaCl)
Covalent Bond
A Covalent Bond is formed when two atoms share one or more pairs of electrons, instead of transferring them completely. Covalent bonds usually form between two non-metals. Depending on how many electron pairs are shared, covalent bonds can be single, double, or triple.
Example: Two Hydrogen atoms share one pair of electrons to form a Hydrogen molecule (H₂). Similarly, Oxygen atoms share two pairs of electrons to form O₂.
Covalent Bond Formation (H₂)
Key Differences Between Ionic and Covalent Bonds
| Basis | Ionic Bond | Covalent Bond |
|---|---|---|
| Formation | Electrons are transferred from one atom to another | Electrons are shared between atoms |
| Formed Between | Metal and Non-metal | Non-metal and Non-metal |
| Charged Particles | Forms ions (cation and anion) | No ions formed; atoms remain neutral |
| Melting/Boiling Point | High | Generally Low |
| Electrical Conductivity | Conducts electricity when dissolved in water or melted | Usually does not conduct electricity |
| Example | NaCl (Sodium Chloride) | H₂O (Water), CO₂ (Carbon Dioxide) |
Why This Topic Matters
Chemical Bonding explains how elements combine to form all the compounds we know, and directly connects back to Atomic Structure (via valence electrons) and forward to chemical formulas and reactions. This makes it one of the highest-weightage chemistry topics for TLT, ECT, PST, and JEST exams.
Practice MCQs
1. Which type of bond is formed by the transfer of electrons?
a) Covalent Bond b) Ionic Bond c) Metallic Bond d) Hydrogen Bond
2. An Ionic Bond usually forms between:
a) Two metals b) Two non-metals c) A metal and a non-metal d) Two noble gases
3. In a Covalent Bond, atoms:
a) Transfer electrons completely b) Share pairs of electrons c) Do not interact d) Lose all electrons
4. A positively charged ion formed by losing electrons is called a/an:
a) Anion b) Cation c) Molecule d) Isotope
5. Which of the following is an example of a Covalent compound?
a) NaCl b) KCl c) H₂O d) MgO
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