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Edexcel International A Level Chemistry

Shapes of Molecules

Molecular shape depends on the number of bonding pairs and lone pairs around a central atom. These pages separate the key geometries so that students can revise electron-pair repulsion, bond angles and how lone pairs change the final shape.

Exam Unit
Unit 1
WCH11/01 – IAS
Specification Points
3.16 – 3.19
4 points covered
Sub-topics
11 lessons
Revision notes available
Exam Board
Edexcel International
Pearson International

Revision Notes

11 revision notes, in the order the specification teaches them.

A linear molecule with two atoms in a straight line
1

Linear

Revise linear molecules with two bonding regions around the central atom and a bond angle of 180°.

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A trigonal planar molecule with three atoms around a centre
2

Trigonal Planar

Learn trigonal planar geometry, where three bonding regions arrange at 120° around the central atom.

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A tetrahedral molecule with four atoms around a centre
3

Tetrahedral

Revise tetrahedral molecules with four bonding pairs and bond angles of about 109.5°.

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A pyramidal molecule with three atoms and one lone pair
4

Trigonal Pyramidal

Understand how one lone pair changes a tetrahedral electron-pair arrangement into a trigonal pyramidal shape.

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A bent molecule with two atoms and two lone pairs
5

Bent

Learn how lone pairs compress bond angles and produce bent or V-shaped molecules such as H₂O.

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A trigonal bipyramidal molecule with five atoms
6

Trigonal Bipyramidal

Revise five-region electron-pair geometry with axial and equatorial positions.

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An octahedral molecule with six atoms
7

Octahedral

Learn octahedral geometry, where six bonding regions arrange at 90° around the central atom.

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A square planar molecule with two lone pairs
8

Square Planar

Revise square planar shapes formed from octahedral electron-pair arrangements with two opposite lone pairs.

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A square pyramidal molecule with one lone pair
9

Square Pyramidal

Understand square pyramidal molecules and how one lone pair affects an octahedral arrangement.

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A T-shaped molecule with two lone pairs
10

Distorted T

Learn distorted T-shaped molecules where lone pairs alter the arrangement of bonding pairs around the central atom.

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A seesaw molecule with one lone pair
11

SeeSaw

Revise seesaw shapes formed from trigonal bipyramidal electron-pair arrangements with one lone pair.

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Summary Map

Download, print and revise the key facts of this topic at a glance.

Summary map

Download, print and revise the key facts of this topic at a glance.

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Summary map · PDF

Shapes of Molecules Map

Edexcel International A Level Chemistry · Unit 1 · Topic 3C Shapes of Molecules

The whole section on one A4 page: electron-pair repulsion, every shape from two to six pairs, lone pairs, related species and polar molecules.

Download the map6 key ideas + a table of shapes · A4 portrait · print ready

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Virtual Lessons

Recorded video lessons that teach the topic step by step.

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Virtual Lessons

Taught step by step in 2 recorded video lessons, to watch at your own pace.

Topic 3C Shapes of Molecules taught by a specialist chemistry teacher, in 2 recorded video lessons that follow the specification.

  • Learn it before you revise itEach lesson explains the chemistry step by step, with the diagrams, mechanisms and worked examples the exam expects.
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MCQ Bank

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Test yourself: 2 MCQ papers

Exam-style multiple-choice papers, marked the moment you submit with every answer explained. MCQ (A) is free.

2 exam-style multiple-choice papers, MCQ (A) to (B): 42 questions on Topic 3C Shapes of Molecules, written the way the exam asks them.

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  • Revise what you missedEach explanation links to the revision notes for that point.
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SAQ Bank

Written, drawn and worked exam practice on this topic, marked by a specialist chemistry teacher.

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Written and drawn answers: 3 papers

Draw, write and calculate the way the exam asks, then a specialist chemistry teacher marks your work.

3 exam papers, (A) to (C): 34 questions on Topic 3C Shapes of Molecules with no multiple choice. You write explanations, work out calculations and draw answers: structures, mechanisms and diagrams.

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Specification

Every specification point in this topic, in the exam board's own words. Rate how confident you are with each one.

Self-assessment · 14 points

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3.16

  1. a

    understand the principles of electron-pair repulsion theory

    Revise
  2. b

    use electron-pair repulsion theory to interpret shapes of simple molecules and ions

    Revise
  3. c

    use electron-pair repulsion theory to predict shapes of simple molecules and ions

    Revise

3.17

  1. b

    understand the term 'bond angle'

    Revise

3.18

  1. a

    know and be able to explain the shape of, and bond angle in, BeCl2

    Revise
  2. b

    know and be able to explain the shape of, and bond angle in, BCl3

    Revise
  3. c

    know and be able to explain the shape of, and bond angle in, CH4

    Revise
  4. d

    know and be able to explain the shape of, and bond angle in, NH3

    Revise
  5. e

    know and be able to explain the shape of, and bond angle in, NH4+

    Revise
  6. f

    know and be able to explain the shape of, and bond angle in, H2O

    Revise
  7. h

    know and be able to explain the shape of, and bond angle in, gaseous PCl5

    Revise
  8. i

    know and be able to explain the shape of, and bond angle in, SF6

    Revise

3.19

  1. a

    be able to apply electron-pair repulsion theory to predict the shapes of molecules and ions analogous to those in 3.18

    Revise
  2. b

    be able to apply electron-pair repulsion theory to predict the bond angles in molecules and ions analogous to those in 3.18

    Revise