H2 Chemistry Notes: CORE IDEA 2, Topic 2 - Chemical Bonding

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10 Feb 2025, 00:00 Z

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Q: What does H2 Chemistry Notes: CORE IDEA 2, Topic 2 - Chemical Bonding cover?
A: Consolidate VSEPR shapes, bond polarity, intermolecular forces, and lattice energy trends for Core Idea 2 (Chemical Bonding) in the 2026 H2 Chemistry syllabus.

Chemical bonding connects atomic structure to macroscopic behaviour: lattice energies govern melting points, molecular geometry decides intermolecular forces, and bond polarity predicts reaction pathways. This note organises the skills required for Paper 2 and Paper 3 questions, supported by exam-style worked examples. For the full set of H2 Chemistry revision resources, refer to https://eclatinstitute.sg/blog/h2-chemistry-notes.

Status: SEAB H2 Chemistry (9476, first exam 2026) syllabus and Chemistry Data Booklet last checked 2026-01-13 (both PDFs last modified 2026-01-13). Core Idea 2 expectations remain assessed across Papers 1–3.

1 Types of Chemical Bonds

Bonding model	Key features	Typical exam focus
Ionic	Electrostatic attraction between cations and anions in a lattice.	Explaining trends in melting point, solubility, conductivity.
Covalent	Shared pair(s) of electrons between atoms.	Bond polarity, molecular shape, sigma vs pi bonds.
Metallic	Lattice of positive ions in a sea of delocalised electrons.	Conductivity, malleability, strength across the periodic table.

1.1 Lattice Energy Trends

Lattice energy measures enthalpy change when one mole of ionic solid separates into gaseous ions. A simplified Born-Landé equation highlights core dependencies:

The lattice energy U is roughly proportional to (

Steric number	Electron-domain geometry	Common shapes	Bond angles
3	Trigonal planar	Trigonal planar, bent	$\pu{120^\circ}$ , $\pu{<120^\circ}$
4	Tetrahedral	Tetrahedral, trigonal pyramidal, bent	$\pu{109.5^\circ, 107^\circ, 104.5^\circ}$
5	Trigonal bipyramidal	Seesaw, T-shaped, linear	$\pu{120^\circ}$ and $\pu{90^\circ}$ combinations
6	Octahedral	Square pyramidal, square planar	$\pu{90^\circ}$

IMF	Requirements	Relative strength	Example
London dispersion	Present in all molecules; induced dipoles.	Weakest; increases with molecular mass and surface area.	$\ce{I2}$
Permanent dipole-dipole	Polar molecules with permanent dipoles.	Medium.	$\ce{CH3Cl}$
Hydrogen bonding	$\ce{H}$ bonded to $\ce{N}$ , $\ce{O}$ , or $\ce{F}$ ; lone pair on adjacent molecule.	Strongest IMF; drives high boiling points.	$\ce{H2O}$

H2 Chemistry Notes: CORE IDEA 2, Topic 2 - Chemical Bonding

1 Types of Chemical Bonds

1.1 Lattice Energy Trends

1.2 Covalent Bond Strength and Length

2 Molecular Geometry and Polarity

2.1 VSEPR Workflow

2.2 Bond Polarity and Molecular Dipole

3 Intermolecular Forces (IMF)

4 Worked Multi-Part Example

5 Exam Tactics

6 Frequent Misconceptions

7 Quick Drill Set

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