Intermolecular Bonding Flashcards
How strong are Intermolecular Bonds?
They are weak when compared to Ionic and Covalent bonds.
What are the 3 types of Intermolecular Forces?
Hydrogen Bonds
Permanent dipole-dipole forces
Van Der Waals forces
How strong are Hydrogen bonds compared to Ionic and Covalent?
They are 20x weaker.
How strong are Dipole-Dipole forces compared to Ionic and Covalent?
They are 100x weaker.
How strong are Van Der Waals forces compared to Ionic and Covalent?
1000x weaker
What sort of intermolecular forces occur between polar molecules?
Permanent dipole-dipole forces and Van der waals
Between what sort of molecules does dipole-dipole forces happen?
Between polar molecules
What sort of forces exist in non-polar molecules?
Van der waals
In what sort of molecules do Van der waals forces occur between?
All molecules have van der waals forces
Define an Intermolecular force.
An intermolecular force is an attractive force between neighbouring molecules
Define a permanent dipole-dipole force.
A permanent dipole-dipole force is a weak attractive force between permanent dipoles in neighbouring polar molecules.
Define a Van der Waals force.
Van der Waals forces are attractive forces between neighbouring molecules caused by induced dipoles.
What is an instantaneous dipole?
An instantaneous dipole is the areas of high and low concentrated negative chard caused by the movement of electrons.
What is an induced dipole?
An induced dipole is a polar region where there is more or less negative charge caused by electrons because of the repelling effect of an instantaneous dipole.
What causes Van der Waals forces?
The movement of electrons creates instantaneous dipoles, which induce induced dipoles. The induced dipoles are then attracted to each other, creating a small force.
What can increase the Van der Waals forces between molecules?
Having more electrons in a molecule. The more electrons the larger the induced dipoles and therefore the greater attraction.
Also having a larger molecule. Larger molecule= more points of contact.
Why does having more electrons create larger Van der Waals forces?
Because with more electrons the induced dipoles are larger. This means there is more attraction between the dipoles and this attracting IS the Van der Waals force.
What is the trend for boiling point in the Noble gases?
As you head down they have a higher boiling point.
What causes the trend in the noble gases boiling points?
Van der Waals forces.
Because there is more electrons lower down the group the induced dipoles are larger, therefore the attraction is also larger. This means the Van der Waals forces are more strong.
Define a Hydrogen Bond.
A hydrogen bond is a strong dipole-dipole attraction between a Hydrogen atom a delta charge and a lone pair of electrons on a highly electronegative atom. This is between different molecules.
What sort of line represents a Hydrogen bond in a diagram.
Dotted lines.
Name an effect of hydrogen bonding on waters properties.
- Ice is less dense than liquid water because the lattice reduces density
- It has relatively high mp and bp because of the extra forces
- A relatively high surface tension and viscosity
Why does Hydrogen bonding make Ice less dense than Water?
When water is Ice it is held in a lattice, but when it is a liquid these hydrogen bonds are broken. This means they are less dense as a solid as the lattice spreads them out.
Why does hydrogen bonding give water a high bp and mp?
Because the Hydrogen bonds create more intermolecular forces that need to be overcome to change the state by melting or boiling.
