Grade 11 Physical Sciences · Matter and Materials

Predict molecular shape

Predict the shape of a molecule from its electron pairs, such as linear, tetrahedral or angular (water is angular).

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Molecular shapes VSEPR Theory Grade 11 ChemistryMiss Martins Maths and Science

Intermolecular Forces grade 11: VSEPR # 1Kevinmathscience

Molecular Geometry Made Easy: VSEPR Theory and How to Determine the Shape of a Moleculeketzbook

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Question WE8 · Siyavula Grade 11 Physical Sciences, 3.2 Molecular shape, Worked example 8 · 3 marks

WE8 Determine the shape of a molecule of

NH_{3}

(3)

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More past paper questions: predict molecular shape

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3. Question WE7 · Siyavula Grade 11 Physical Sciences, 3.2 Molecular shape, Worked example 7 · 3 marks
WE7 Determine the shape of a molecule of $BF_{3}$ (3)
Show the memo (3 ticks)Memo
1. ✓
  Electron pairs around the central atomDraw the Lewis diagram: the central atom is boron.
  There are three electron pairs and no lone pairs around the central atom.
  1 mark · Draw Lewis diagrams
2. ✓
  General formulaThe molecule has the general formula $AX_{3}$ .
  1 mark · Predict molecular shape
3. ✓
  ShapeThe molecular shape of $BF_{3}$ is trigonal planar.
  1 mark · Predict molecular shape
4. Question WE12 · Siyavula Grade 11 Physical Sciences, 3.3 Electronegativity, Worked example 12 · 3 marks
WE12 State whether hydrogen cyanide ( $HCN$ ) is polar or non-polar.(3)
Show the memo (3 ticks)Memo
1. ✓
  ShapeThe molecule is linear. There are four bonding pairs, three of which form a triple bond and so are counted as $1$ . There is one lone pair on the nitrogen atom.
  1 mark · Predict molecular shape
2. ✓
  Bond polaritiesThe electronegativity difference between carbon and hydrogen is $0, 4$ and between carbon and nitrogen is $0, 5$ . Both of the bonds are polar.
  1 mark · Determine bond and molecule polarity
3. ✓
  Molecule polarityThe molecule is not symmetrical and so is polar.
  1 mark · Determine bond and molecule polarity
5. Question WE10 · Siyavula Grade 11 Physical Sciences, 3.3 Electronegativity, Worked example 10 · 3 marks
WE10 State whether hydrogen ( $H_{2}$ ) is polar or non-polar.(3)
Show the memo (3 ticks)Memo
1. ✓
  ShapeThe molecule is linear. There is one bonding pair of electrons and no lone pairs.
  1 mark · Predict molecular shape
2. ✓
  Bond polarityHydrogen: $2, 1$ . There is only one bond and the electronegativity difference is $0$ .
  The bond is non-polar.
  1 mark · Determine bond and molecule polarity
3. ✓
  Molecule polarityThe molecule is non-polar.
  1 mark · Determine bond and molecule polarity
6. Question WE11 · Siyavula Grade 11 Physical Sciences, 3.3 Electronegativity, Worked example 11 · 4 marks
WE11 State whether methane ( $CH_{4}$ ) is polar or non-polar.(4)
Show the memo (4 ticks)Memo
1. ✓
  ShapeThe molecule is tetrahedral. There are four bonding pairs of electrons and no lone pairs.
  1 mark · Predict molecular shape
2. ✓
  Electronegativity differenceThere are four C–H bonds, so only one difference is needed: $2, 5 - 2, 1 = 0, 4$
  1 mark · Determine bond and molecule polarity
3. ✓
  Bond polarityEach bond is polar.
  1 mark · Determine bond and molecule polarity
4. ✓
  Molecule polarityThe molecule is symmetrical and so is non-polar.
  1 mark · Determine bond and molecule polarity

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