Intermolecular forces Flashcards
What are intermolecular forces?
Forces occurring between molecules
Where do intermolecular forces only occur in?
Simple covalent substances
What are the bonds called that hold together atoms by a shared pair of electrons?
Covalent bonds
What are the 3 types of intermolecular forces?
Induced dipole dipole
Permanent dipole dipole
Hydrogen bonding
Are induced dipole dipole forces temporary or permanent?
Temporary
What type of molecules do induced dipole dipole forces occur between?
All molecules
Why do induced dipole dipole forces act for a short time?
Electron density is constantly changing
Are induced dipole dipole forces strong or weak?
Weakest type of intermolecular force
What type of forces interact through symmetrical molecules/non-polar molecules?
Induced dipole dipole interactions
Why does the boiling point increase when there are induced dipole dipole forces?
More energy is needed to disrupt the forces between the molecules
How do induce dipole dipole interactions arise?
Electrons in a molecule are constantly moving
Electron distribution may be unsymmetrical at any one instant
produces a temporary dipole in that molecule
if another molecule approaches the molecule with the c5::temporary dipole, an opposite dipole is induced into the neighbouring molecule
What two factors increase the strength of induced dipole dipole interactions?
Increase in the number of electrons in the molecule or atom
Increase in the surface contact of the molecules or atoms
What are polar bonds?
Covalent bond between atoms with different electronegativity
What is definition of electronegativity?
The ability of an atom to attract the bonding electrons in a covalent bond
what results in the differences in electronegativity?
A dipole is the separation of charge in a bond which occurs
When does electronegativity increase?
Across a period
When does electronegativity decrease?
Down a group
What element has the highest electronegativity?
Fluorine
What element has the lowest electronegativity?
Francium
What are polar molecules?
Unsymmetrical molecules whose dipole don’t cancel out
Where do electrostatic forces of attraction act between in polar molecules?
Opposite charges of the neighbouring molecules
What will happen to the overall permanent dipole if the molecule is symmetrical?
Dipoles will cancel each other out
There will be no overall permanent dipole
Molecule is now non-polar
Do symmetrical molecules have any lone pairs on the central atom?
No
Are all the atoms around the central atom the same or different in symmetrical molecules?
Same
