4.4 Intermolecular Forces Flashcards
What do the intermolecular forces determine
Physicals properties such as:
Volatility
Solubility
Conductivity
What intermolecular force occurs in non polar molecules
London dispersion forces
Why doesn’t Cl2 have a permanent dipole?
Because the electrons are equally shared due to the equal electronegativity values
What is a temporary induced dipole?
Electrons are like mobile clouds of negative charge and at certain points the density of the cloud may become greater. This creates a weak dipole which is also known as a TEMPORARY INDUCED DIPOLE
Other names for temporary induced dipole?
Weak dipole / instantaneous dipole
What forces are between temporary dipoles?
Weak London dispersion forces
Do temporary dipoles have a high of low melting and boiling point?
Low because it requires very little energy to break the London dispersion forces
What molecules do dipole - dipole attractions occur in?
Polar molecules
What are van dear waals?
A general term for dipole-dipole and London dispersion forces and also represents a dipole-induced forces
When does hydrogen bonding occur?
In molecules where there is an hydrogen atom and an extreme electronegative element such as N,O and F
Why does hydrogen bonding occur?
The large electronegativity difference causes the electrons to be pulled away from the hydrogen, due it its small size and lack of shielding the hydrogen excerpts an attractive force onto the lone pair of the N,O or F
Describe ice
Can form up to 4 hydrogen bonds Tetrahedral structure Open structure Less dense than water Expanded by 9%
What do giant covalent structures have high melting points?
Because of the strong covalent bonds take a lot of energy to be broken in order to change its state
Why do non polar substance dissolve in non polar solvents?
The weak London dispersion forces between the solute and the solvent
Why do polar substances dissolve in polar solvents?
Because they interact through dipoles and hydrogen bonding
