Chapter 2 Flashcards
Covalent bonding
a bond between non-metallic atoms that form when atoms share electrons to achieve a stable outer shell
dipole–dipole interactions
weak bonding caused by the positive end of one dipole attracting the negative end of another dipole and are found only in polar discrete molecules.
dispersion force
the bond between adjacent molecules formed by instantaneous dipoles. Are found in all atoms or discrete molecules and increase with the size of the atom or molecule and the corresponding number of electrons.
hydrogen bonding
the bond between a hydrogen atom covalently bonded to an atom of F, O or N and another molecule that also contains an atom of H, F, O or N.
intermolecular forces
forces that exist between molecules
intramolecular bonding
internal bonds within a molecule
non-polar covalent bonds
formed between atoms with the same electronegativity
non-polar molecule
molecule that does not have permanent dipoles or is symmetrical
polar covalent bond
formed when two atoms that have different electronegativities share electrons unevenly
polar molecule
a molecule which, due to its polar bonds and its asymmetric shape, has an overall imbalance in the distribution of its electrons
polarity
localised imbalances in electric charges within a molecule resulting in a negatively charged end and positively charged end
VSEPR theory
used to predict the shape of a molecule based on minimising electron repulsions around a given atom in a molecule
Physical properties of molecular substances
have low melting and boiling points due to weak intermolecular forces and do not conduct electricity because the molecules are electrically neutral
Diamond
Bonds with four other carbon atoms, therefore cannot conduct electricity as there is no delocalised electrons and are used for cutting, sawing and drilling through hard materials
Graphite
Graphite is bonded to three other carbon atoms therefore can conduct electricity due to the delocalised electrons and typically used for ‘lead’ in pencils.
Graphite properties
is solid with a high melting point due to strong covalent bonds
where is hydrogen bonding found?
only in molecules where a hydrogen atom is directly bonded to a more electronegative fluorine, oxygen or nitrogen atom. These bonds are stronger than other dipole-dipole bonds and result in higher melting and boiling points.
