Intermolecular Forces Flashcards
Intermolecular forces
A weak force of attraction between molecules, ions or atoms of noble gases
Diople-dipole
Attractive forces between polar molecules
London Forces/ Induced dipole/dispersion
Non polar molecules combine and their electron clouds repel each other and distort to have slightly changed sides and a momentary dipole is created
Special case of dipole-dipole
Hydrogen bonding:
hydrogen is bonded to:
- a small atom
- of high electronegativity (increases surface area, increases boiling point)
- with at least one lone pair of electrons
N2,O2,F2
What affects the strength of these forces?
The number of electrons:
- The molecular mass-larger electron cloud density-more electrons=stronger
- Surface area- more points of contact-more electrons=stronger
Difference between INTRAMOLECULAR forces and INTERMOLECULAR forces?
IMF- weak forces of attraction between molecules, ions or atoms of noble gases
Intramolecular- forces of attraction inside molecules
Crystal lattice
The 3D spatial arrangement of the particles in the solid
Molecular solids
Made of molecules
London or hydrogen
Soft, low melting points
I2,H20(ice)
Network solids
Made of atoms
Have covalent bonds
Graphite and Diamond
Hard, high melting point (overcome strong covalent bonds)
Ionic solids
Made of cations and anions
High melting points, brittle
Copper 2 Sulphate, Sodium chloride
Metallic solids
Made of positive atomic kernels
It has metallic bonds
Good conductors, high melting points
What makes the attractive forces within a crystal lattice strong?
Due to the close proximity of the cations and ions and therefore there is lots of energy required to overcome these attractive forced hence they are very strong
