Chapter 6 - Intermolecular forces and allotropy Flashcards
What is allotropy?
The existence of two or more physically distinct forms of the one element in the same physical state.
What are allotropes?
Forms of the one element that have distinctly different physical properties (colour, density, hardness, electrical conductivity).
What is hydrogen bonding?
A type of intermolecular force that involves a hydrogen atom bonded to an O, N or F atom in one molecule becoming attached to an O, N or F atom in a different molecule.
What is dispersion force?
Weak intermolecular force that arise from electrostatic attractions between instantaneous dipoles in neighbouring molecules.
What are dipole-dipole forces?
The attractive electrostatic forces between polar molecules.
What is valence shell electron-pair repulsion theory?
Pairs of valence electrons around an atom in a molecule arrange themselves spatially so as to get as far away from one another as possible, and this determines the shape of the molecule.
What is a lone pair?
A lone pair is a pair of atoms not used in bonding.
What is a non-polar bond?
When electrons are more equally shared between atoms.
What is a non-polar molecule?
Molecules that do not have any electrical charges or partial charges
What is a polar molecule?
A molecule that has a net dipole.
What is a dipole?
A pair of equal and opposite charges separated in space.
What are polar covalent bonds?
Covalent bonds in which the electrons are unequally shared.
How do electronegativities determine whether or not a covalent bond will be polar?
If two elements forming a covalent bond have different electronegativities, then the shared pair of electrons will be attracted towards the element with the higher electronegativity, therefore the bond will be polar.
What are the three types of intermolecular forces?
Hydrogen bonds, Dipole-dipole and dispersion forces.
What are the strengths of each intermolecular force?
- Hydrogen bond
- Dipole-dipole
- Dispersion forces
