Podcast
Questions and Answers
In the VSEPR theory, what happens to bond angles when there are lone pairs present?
What is the shape of a molecule with 4 electron pairs and only 3 bonds?
How does the VSEPR theory explain the shapes of molecules with lone pairs?
What is the shape of a molecule with 5 electron pairs?
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Which pair experiences the most repulsion in molecules with multiple lone pairs?
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What is the effect of having more than one lone pair in a molecule?
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How does the presence of lone pairs impact the final shape of a molecule?
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What is the impact of lone pairs on bond angles?
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Which molecule shape involves a 'trigonal pyramid' configuration?
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How does lone pair positioning affect molecular geometry?
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Study Notes
Structure and Properties
- The physical properties of a substance depend on the structure and bonding of the atoms or molecules.
- The properties of metallic, ionic, and giant covalent structures depend on the strength and type of bonding between the atoms or ions.
Atomic Radius
- The radius of an atom depends on the nuclear charge (Z) and shielding.
- Nuclear charge pulls electrons towards the nucleus, while shielding is a repulsive charge between electrons.
Trends Across a Period
- As more protons are added to the nucleus, the nuclear charge increases.
- Shielding is similar because the same outer energy level is being filled.
- The outer electrons are pulled closer to the nucleus, resulting in a decrease in atomic radius.
Trends Down a Group
- As more protons are added to the nucleus, the nuclear charge increases.
- Shielding also increases due to more filled core electron shells.
- The increase in repulsion outweighs the increase in attraction from the nucleus, resulting in an increase in atomic radius.
Trends in Atomic Radii
- Atomic radius increases down a group.
Miscibility
- When two liquids mix completely, they are miscible.
- If two liquids form two phases, they are immiscible.
- The system will do what gives the strongest total molecular forces.
Solubility
- Solubility is a measure of how much of a solute dissolves in a solvent.
- It is determined by intermolecular forces, among other factors.
Shapes of Molecules
- The shape of a molecule is determined by the repulsion between pairs of electrons in the outer shell (VSEPR theory).
- Electron pairs arrange themselves to minimize repulsion, resulting in a specific shape.
3-Dimensional Shapes
- For 4+ electron pairs, 3-dimensional shapes are required.
- Examples include tetrahedral, trigonal bipyramidal, and octahedral shapes.
Shape of Ions
- If a molecule is charged, an electron must be added or subtracted before working out the number of electron pairs.
- This affects the shape of the ion.
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Description
This quiz challenges you to predict which molecule between Cl2 and I2 will have the highest boiling point, and to explain the difference. It also asks why pentane has a higher boiling point than 2,2-dimethylpropane despite having the same formula. Test your understanding of intermolecular forces and boiling points.
