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Chemistry ATAR U1 > IMF > Flashcards

IMF Flashcards

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1
Q

What Does Molecular Shape Depend On

A

Number of atoms in molecule

Number of bonds from the central atom

Number of unbonded pairs of electrons around central atom

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2
Q

What Does VSEPR Theory Stand For

A

Valence Shell Electron Pair Repulsion Theory

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3
Q

What is the VSEPR Theory

A

Electron pairs in valence shell of atom repel each other
- So arranged as far apart as possible so they don’t repel, giving most stable configuration

  • Repel because like charges repel
  • Lone pairs repel other electrons more
  • Electron pairs repel as far as possible, forming different molecular shapes
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4
Q

What are the 6 Molecular Shapes of Atoms

A

Trigonal Planar

Tetrahedral

Pyramidal

V-Shaped (Bent)

Linear (2 Atoms)

Linear (3 Atoms)

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5
Q

What is Trigonal Planar

A

3 atoms around the central atom

No unbonded pairs of electrons

Approx 120 degrees between each atom

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6
Q

What is Tetrahedral

A

4 atoms around the central atom

No unbonded pairs of electrons

Approx 109.5 degrees between each atom

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7
Q

What is Pyramidal

A

3 atoms around central atom

1 unbonded pair of electrons

Approx 109 degrees between each atom

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8
Q

What is V-Shaped (Bent)

A

2 atoms around central atom

Can have 1 unbonded pair, with approx 120 degrees between each atom

Can have 2 unbonded pairs, with approx 109 degrees between each atom

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9
Q

What is Linear (2 Atoms)

A

Diatomic molecules

Linear molecule, regardless of unbonded pairs

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10
Q

What is Linear (3 Atoms)

A

3 atoms in molecule

Approx 180 degrees between each atom

No unbonded pairs of central atom

Bonds on either side repel each other

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11
Q

How Do You Identify Molecular Shape From Formula

A

2 Methods:

Method #1:
1) Identify central atom
2) Identify umber of valence electrons in central atom
3) Identify number of bonding electrons in central atom
4) Identify number of lone electron pairs in central atom
5) Use properties of each molecular shape to determine

Method #2:
1) Draw electron dot diagram
2) Identify number of bonding & non-bonding pairs of electrons around central atom
3) State and explain the shape

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12
Q

What are Intermolecular Bonds

A

Bonds between different molecules

Weak bonds, have different types

Uses dotted line to draw

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13
Q

What are Intramolecular Bonds

A

Bonds within a molecule

Strong bonds, have different types (Covalent, Metallic, Ionic)

Uses full line to draw

Used to determine chemical properties of molecule

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14
Q

What is Polarity & Dipole

A

A molecule with imbalanced charge distribution is said to be polar

Dipole is the separation of positive and negative charges

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15
Q

How is Electronegativity Used to Predict Bond Polarity, where the two atoms have the same electronegativity

A

Predicts the polarity of the intermolecular bonds

If the 2 atoms have same electronegativities = Bond between them is non-polar

  • As electrons shared equally between atoms, no dipole created
  • Only diatomic molecules, as that’s the only way to have same electronegativity (Eg. O2)
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16
Q

How is Symmetry Used to Predict the Molecular Polarity, Where The Molecule is a Diatomic Molecule

A

Predicts the polarity of whole molecules

If the molecule is a diatomic molecule, depends on polarity of bond between those two atoms

  • Polar bond = Polar molecule
  • Non-Polar bond = Non-Polar molecule
17
Q

What is the Polarity of a Bond where 2 Atoms Have Different Electronegativities

A

If the 2 atoms have different electronegativities = Bond between them is polar

  • As electrons are closer to more electronegative atom, not equally shared
  • More electronegative side is -ve charged, other side +ve charged, creating a dipole
  • Higher difference in electronegativity = Higher polarity
18
Q

How is Symmetry Used to Predict the Molecular Polarity, Where The Molecule is a Symmetrical Polyatomic Molecule

A

If the molecule is a polyatomic molecule and is symmetrical, is a non-polar molecule

  • Non-Polar bonds don’t create any dipole, so they stay as they are
  • The individual dipoles with the polar bonds cancel out perfectly, as the atom is symmetrical, creating a non-polar molecule
  • “Not all molecules with polar bonds are polar”
19
Q

How is Symmetry Used to Predict the Molecular Polarity, Where The Molecule is a Asymmetrical Polyatomic Molecule

A

If the molecule is a polyatomic molecule (More than 2 atoms) and is asymmetrical, is a polar molecule

  • Has net dipole, charges don’t cancel each other out
  • Has uneven charge distribution in molecule
  • Must have polar bonds, as these polar bonds create a dipole
20
Q

What are Dispersion Forces

A

Temporary/Instantaneous dipoles, where electrons have random movement around a molecule

Electrons eventually will gather closely at one end, becoming negative side, other side is positive side = Dipole

Electrons in next molecule are pushed to the far end due to electrostatic repulsion, creating another dipole

These dipoles are held together by attraction between the positive and negative dipoles of different molecules

21
Q

What are properties of dispersion forces

A

High vapour pressure, as weak IMF, so molecules are held weakly on the surface, so easy to escape

Low melting and boiling point, weak IMF

Non-Polar to Non-Polar solubility, where dispersion forces between solute & solvent sufficient to disperse solute particles through solvent

22
Q

What are Dipole-Dipole forces

A

Moderate vapour pressure, where it is a moderate IMF, so molecules are held moderately tight on surface, fairly hard to escape

Medium melting & boiling point, as moderate IMF

Is 10x weaker than Hydrogen Bonding

Polar to Polar solubility, where Dipole-Dipole forces between solute & solvent molecules strong enough to overcome solute-solute & solvent-solvent interactions

23
Q

What is hydrogen bonding

A

Electrostatic attraction of hydrogen atoms bonded to Nitrogen, Oxygen, Fluoride (NOF) molecules, and their lone pairs

24
Q

What is process of hydrogen bonding

A

1) Hydrogen bonded to NOF molecule

2) NOF molecule more electronegative, withdraws shared electrons = Dipole

3) Hydrogen has unshielded nucleus, also large magnitude positive dipole

4) Attracted to lone pairs of other NOF molecules (As they have negative dipoles, and lone pairs of electrons)

= Chain of Hydrogen bonds

25
Q

What are properties of hydrogen bonding

A

Strongest IMF, relatively high melting & boiling point

Low vapour pressure, as strong IMF so molecules held tighter together, so harder to escape surface

Polar to Polar solubility, where Hydrogen bonding forces between solute & solvent molecules sufficient enough to overcome solute-solute and solvent-solvent interactions

26
Q

How can you compare different IMF strengths

A

Higher boiling point = Stronger bond

  • Boiling point is best indicator, as all bonds are broken at boiling point

Condensed state, only held by IMF forces

Chemistry ATAR U1 (5 decks)

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