structure and bonding Flashcards
a covalent bond is…
two positive nuclei being held together by their common attraction for a shared pair of electrons.
polar covalent bonds are formed when…
the attraction of the atoms for the pair of bonding electrons is different. delta positive and delta negative notation is used to indicate the partial changes on atoms, which give rise to a dipole.
how to tell how polar a bond will be
the difference between the electronegativities between the bonded atoms
ionic bonding is the…
electrostatic attraction between positive and negative ions.
london dispersion forces are…
- formed as a result of electrostatic attraction between temporary dipoles and induced dipoles caused by the temporary dipole repelling the electrons of a neutral atom pushing them to the other side of the atom.
- forces of attraction that operate between all atoms and molecules.
the strength of a london dispersion force is related to…
the number of electrons within an atom or molecule.
diatomic molecules
FIBNOCH
what is an intra molecular force ?
an attractive force that acts between the atoms within the molecule
what is an inter molecular force ?
forces of attraction that act between the molecules
why does fullerene have a high mp/bp?
because there are a large number of carbon atoms in each molecule;e meaning a large number of electrons resulting in an increase in the strength of the ldfs between molecules.
describe fullerene
- covalent molecule
- high mp and bp for a covalent molecule
- contains only ldfs that are strong due to the sheer number of carbon atoms (meaning there are more electrons and thus stronger ldfs.)
describe diamond
- covalent network structure
- high mp and bp due to the face that there is a great amount of energy required to break the covalent bonds that hold the atoms together
describe graphite
- covalent network
- lower mp and bp than diamond because the carbon atoms on each layer are held together by covalent bonds but the layers are held together by weak ldfs.
why does graphite conduct electricity ?
because each carbon within the structure is only bonded to three other carbon molecules, one outermost electron on each carbon atom is not used to make covalent bonds (delocalised.)
describe metallic bonding
a lattice of positive ions with delocalised electrons
what is hydrogen bonding ?
bonds consisting of a hydrogen atom bonded to an atom of a strongly electronegative element (FON)
what is a pure covalent bond
when both atoms involved in covalent bonding are the same or experience the same attractive force from each nuclei as the electronegativities are the same
if the elements within a structure, of the same electronegativity, act in opposite directions from the central element (e.g, in linear, tetrahedral, and angular compounds)…
the structures can be non polar but the BONDS can be polar
what are pdpds?
intermolecular forces of attraction between molecules that have a permanent overall dipole
what can be said about the solubility of two substances that share similar intermolecular forces?
very soluable/ miscible ((in case of liquids))
what can be said about the solubility of molecules within a structure that have very different intermolecular forces??
immiscible
what is viscosity ?
a measure of how much the molecules in a compound stick together.
what type of substances dissolve in water and why?
polar substances dissolve in water as water is also polar- particularly substances with hydrogen bonding.
