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Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2...

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Topic 4: Chemical Bonds IB Chemistry SL Ms. Kiely Coral Gables Senior High
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Page 1: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

Topic 4: Chemical Bonds

IB Chemistry SLMs. Kiely

Coral Gables Senior High

Page 2: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

The diagrams below represent the structures of iodine, sodium, and sodium iodide.

1. State which of the structures correspond to iodine, sodium, sodium iodide.

2. State the type of bonding in each structure.

3. Sodium and sodium iodide can both conduct electricity when molten, but only sodium can conduct electricity when solid. Explain this difference in conductivity in terms of the structures of sodium and sodium iodide.

4. Explain the high volatility of iodine compared to sodium and sodium iodide.

Bell Ringer:Paper 2

Question

Page 3: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

1. A is sodium iodide, B is sodium, C is iodine

2. A – ionic bonding; B – metallic bonding; C – van der Waals’ forces (and covalent bonding);

3. (for Na) (lattice of) positive ions/atoms; delocalized/free electrons/sea of electrons;

(for NaI) oppositely charged ions/positive and negative ions; free to move in molten state

4. forces between I₂ molecules are weak; ionic/metallic bonding strong(er);

[10 Marks Total]

Page 4: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

To be completed in the following groups- please sit as a group:

1) Elaine, Chloe, Harrison2) Yvanna, Pablo, Cameryn3) Zach, Camilo, Vanessa4) Juan, Roxy, Gaby5) Sofia, Nicolas, Sam6) Sarah, Jonathon, Victoria7) Javier, Amaya, Natasha

Pop Quiz Review Activity

Page 5: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

Pop Quiz Review ActivityTo be completed in the following groups- please sit as a group:

1) Lucy, Angelica, Yanik, Daniela2) Venicia, Ximena, Lazaro, Katie3) Juliana, Savannah, Nick, Pranav4) Alicia, Valeria, Magdala, Julio5) Jerica, Edrey, Leila, Sandra6) Sara, Henry, Carlos, Lior8) Oscar, Jocelin, Isabelle (see me)

Page 6: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

POP Quiz 5th Period - 10 minutes1. Draw the Lewis dot structure of sulfur dioxide, SO₂, and state the types of bonds present in the molecule. (3 marks)

2. Based on electronegativity values, which bond is the most polar?A. B―C B. C―O C. N―O D. O―F (1 mark)

3. When C₂H₄, C₂H₂ and C₂H₆ are arranged in order of increasing C–C bond length, what is the correct order?A. C₂H₆, C₂H₂, C₂H₄B. C₂H₄, C₂H₂, C₂H₆C. C₂H₂, C₂H₄, C₂H₆D. C₂H₄, C₂H₆, C₂H₂ (1 mark)

Page 7: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

POP Quiz 5th Period1.

2. B. C―O because C and O are the only ones NOT right next to each other.

3. C. C₂H₂, C₂H₄, C₂H₆

1 coordinate bond and 1 double bond.Important: Coordinate bonds are considered to be no different from other covalent bonds. So you will often see them illustrated just like a single covalent bond instead of an arrow.

Page 8: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

POP Quiz 7th Period - Pop Quiz1. Draw the Lewis dot structure of sulfur dioxide, SO₂, and state the types of bonds present in the molecule. (3 marks)

2. Based on electronegativity values, which bond is the most polar?A. B―C B. O―F C. N―O D. C―O (1 mark)

3. When C₂H₄, C₂H₂ and C₂H₆ are arranged in order of increasing C–C bond length, what is the correct order?A. C₂H₆, C₂H₂, C₂H₄B. C₂H₂, C₂H₄, C₂H₆C. C₂H₄, C₂H₂, C₂H₆D. C₂H₄, C₂H₆, C₂H₂ (1 mark)

Page 9: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

POP Quiz 7th Period1.

2. D. C―O because C and O are the only ones NOT right next to each other.

3. B. C₂H₂, C₂H₄, C₂H₆

1 coordinate bond and 1 double bond.Important: Coordinate bonds are considered to be no different from other covalent bonds. So you will often see them illustrated just like a single covalent bond instead of an arrow.

Page 10: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

Pg. 136 exercises 18 - 20

Practice

HOMEWORK

Page 11: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

HOMEWORKPg. 136 exercises 18 - 20

Practice

It is the only option that does not

contain a metal.

Page 13: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

VSEPR TheoryRecall that ionic compounds have large crystalline, lattice structures. Covalent molecules, however, are not large lattice crystals; they are discrete molecular units that can have different geometrical shapes.

We use the VSEPR theory to help us deduce the geometrical shape of a molecule.

Valence Shell Electron Pair Repulsion theory: The geometrical shape of a molecule is determined by the repulsion of the electron domains surrounding the central atom of a molecule.

Page 14: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

VSEPR TheoryWhy do we care about the shapes of molecules?

One example:Neurotransmitters are chemicals- they are

molecules! For example, dopamine is a neurotransmitter released by brain cells and

received by other brain cells.

The “message” carried by dopamine can only be received if the receiving neuron has a receptor site that matches the shape of the dopamine

molecule.

Understanding these shapes helps us understand how our brains communicate.

Page 15: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

In order to determine the shape of a molecule, we need to consider the factors in a molecule that determine its shape. These shapes can be found on pg. 137, and will be presented in the slideshow momentarily.

The factors that determine the shape of a molecule are:

-the amount of bonds surrounding the central atom

-the amount of lone pairs surrounding the atom

We collectively call the areas around the central atom that are either occupied by a covalent bond or a lone pair an electron domain.

Electron Domain: a term that refers to all electron locations around the central atom, be they occupied by lone pairs, or by single, double, or triple bonded pairs of electrons.

Water has 4 electron domains surrounding oxygen: 2 are lone pairs, the other 2 are

single bonds.

Page 16: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

Electron Domain: a term that refers to all electron locations around the central atom, be they occupied by lone pairs, or by single, double, or triple bonded pairs of electrons.

If there are lone pairs on the central atom, the electron domain geometry will be different from the molecular geometry.

Page 17: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

180∘

120∘

117∘

109.5∘

107∘

105∘

Pg. 137

Page 18: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

The electron domain geometry is determined by the positions of all the electron domains, whether they are bonds or lone pairs.

The molecular geometry depends only on the positions of the bonded atoms. If bonded atoms have lone pairs near them, then the lone pairs will cause the angles between the atoms to decrease as lone pairs cause more repulsion than do bonded electrons.

Page 19: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

The lewis structures of methane CH₄, ammonia NH₃, and water H₂O all reveal four electron domains. However:

-in methane CH₄, all of the domains around the central atom are bonds-in ammonia NH₃, one of the domains around the central atom is a lone pair-in water H₂O, two of the domains are lone pairs

The two lone pairs in water make water v-shaped, pushing the two hydrogen atoms towards each other due to the strong repulsive force of the lone pairs.

109.5∘

105∘

Page 20: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

Practice: Sample Paper 2 question

Page 21: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

Molecules with polar bonds are not always polar moleculesThe polarity of a molecule depends on:

-the polar bonds that it contains

-the way in which such polar bonds are oriented with respect to each other; in other words, the shape of the molecule

If all the bonds are of equal polarity, and are arranged symmetrically: nonpolar

If the molecule contains bonds of different polarities, OR if the bonds are of equal polarity but are NOT arranged symmetrically due to lone pairs: polar

Page 22: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

Dipole moments can also help us determine whether a molecule is polar or not.

non-polar

polar

Page 23: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

Reflection/practice:

Draw the Lewis structure of each molecule, state the electron domain shape and the molecular domain shape, and bond angles. Then, state whether they will be polar or nonpolar molecules:

1) PH₃

2) C₂H₄

3) ClF

Page 24: Topic 4: Chemical Bonds · IB Chemistry SL Ms. Kiely Coral Gables Senior High. ... Paper 2 Question. 1. A is sodium iodide, B is sodium, C is iodine ... Practice: Sample Paper 2 question.

ANSWERS1) PH₃ ED: tetrahedral, MD: pyramidal, 107°, polar *the dipoles all point towards phosphorous and towards the lone pair on phosphorous: there is a net pull towards phosphorous suggesting polarity

2) C₂H₄ ED: planar triangular, MD: planar triangular, 120°, non-polar *In this case, there are two central atoms. Each C, though, has three electron domains, all of which are bonds (no lone pairs). **the dipoles all point from hydrogen atoms towards the carbon atoms: equal & opposite pulls cancel each other out, no net dipole = non-polar

3) ClF ED: linear, MD: linear, 180°, polar *Two atoms bonded together will always result in a linear shape. **the dipole points towards F, and there are no other atoms to pull. Net dipole means polarity.


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