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Chemical bonding
Chemistry
Useful for: OSSC RHT — Regular High School Teacher, OSEPA Upper Primary — Science, OSSC Science, OSSSC Govt TGT Science — CBZ, OSSSC Govt TGT Science — PCM, SSB Lecturer (Degree Colleges), SSB TGT CBZ, SSB TGT PCM
Overview
Atoms bond to reach stable electron arrangements by transferring electrons (ionic), sharing them (covalent) or pooling them (metallic).
Key points
- Kossel and Lewis explained bonding using the octet rule.
- Ionic bonds form by electron transfer (NaCl).
- Covalent bonds form by sharing electrons (H₂, H₂O, CH₄).
- Polar covalent bonds have unequal sharing due to electronegativity difference.
- Hydrogen bonding gives water its high boiling point.
- VSEPR shapes: CH₄ tetrahedral (109.5°), NH₃ pyramidal (about 107°), H₂O bent (about 104.5°).
Explanation
- Ionic compounds have high melting points and conduct when molten or dissolved.
- Covalent compounds usually have low melting points.
- Metallic bonding explains conductivity and malleability.
- Lone pairs reduce bond angles.
- Double and triple bonds are shorter and stronger.
Step by step
- Identify the concept, method or fact asked.
- Recall the definition, thinker, year or rule.
- Apply it and eliminate extreme or mismatched options.
Examples
- Common salt → ionic bonding.
- Water molecule shape → bent, about 104.5°.
- Ice floats → hydrogen-bonded open structure.
Traps and advanced points
- Trap: Calling NaCl covalent.
- Trap: Wrong bond angles.
- Trap: Ignoring lone pairs.
Quick revision
- Ionic transfer; covalent sharing.
- VSEPR angles 109.5°, 107°, 104.5°.
- Hydrogen bonding.
Practice MCQs
Common salt (NaCl) has —
- covalent bonding
- ionic bonding
- metallic bonding
- hydrogen bonding only
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Answer: (b) ionic bonding. Electron transfer.
A water molecule has a —
- bent shape
- tetrahedral shape
- square shape
- linear shape
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Answer: (a) bent shape. Bent, about 104.5°.
The bond angle in methane (CH₄) is about —
- 104.5°
- 107°
- 109.5°
- 90°
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Answer: (c) 109.5°. Tetrahedral.
The bond angle in ammonia (NH₃) is about —
- 109.5°
- 120°
- 104.5°
- 107°
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Answer: (d) 107°. Pyramidal; one lone pair.
Covalent bonds form by —
- gain of neutrons
- transfer of electrons
- sharing of electrons
- loss of protons
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Answer: (c) sharing of electrons. Sharing.
Water’s high boiling point is due to —
- no bonding
- ionic bonds
- hydrogen bonding
- metallic bonding
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Answer: (c) hydrogen bonding. Hydrogen bonds between molecules.
The octet rule was used to explain bonding by —
- Bohr and Pauli
- Dalton and Avogadro
- Kossel and Lewis
- Newton and Kepler
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Answer: (c) Kossel and Lewis. Kossel–Lewis approach.
Lone pairs on the central atom —
- increase bond angles
- have no effect
- break bonds
- reduce bond angles
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Answer: (d) reduce bond angles. Lone pairs repel more.
Ionic compounds conduct electricity —
- only as gases
- in solid state
- when molten or dissolved
- never
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Answer: (c) when molten or dissolved. Ions must be free to move.
Ice floats on water because of —
- an open hydrogen-bonded structure
- ionic bonds
- metallic bonds
- air bubbles only
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Answer: (a) an open hydrogen-bonded structure. Ice is less dense.
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