Flashcards in CHE - Covalent Bonding Deck (12):
What are the useful properties of graphite?
Conducts electricity in solid state
Soft greasy nature
High melting temperature
Grey opaque solid
What is sublimation?
Ability to go from solid to gas (bypass liquid)
Describe the basics of covalent bonds (electron behaviour, elements)
What is covalency?
The number of electrons it shares when bonding covalently (not rule b/c some elements form multiple different molecules with that same non-metal eg SO2 and SO3)
Eg Cl2 has covalency of one (single bond)
What are the classic examples of each of the valence structure shapes?
Linear: CO2 (carbon dioxide)
V-shaped / angular: H2O (water)
Pyramidal / triangular pyramid: NH3 (ammonia)
Tetrahedral: CH4 (methane)
Planar triangle: BF3
What determines where an electron spends more time in a covalent bond?
Electronegativity (higher = more time = slightly negative > polarised bond)
> two dipoles (molecule = a dipole and polar)
What are the three types of intermolecular forces and when do they apply?
Dispersion forces > non-polar molecules
Dipole-dipole interaction/attraction > polar molecules (opposite ends of molecules line up)
Hydrogen bonds > polar molecules where H is bonded w/ N, O, or F
How do you determine polarity of molecules?
Pos and neg ends > dipole > ASYMMETRICAL > polar
Neg ends only or pos ends only > SYMMETRICAL > non-polar
Why does hydrogen bonding occur?
N, O, F are highly electronegative > highly polarised bonds > large positive charge on H > N, O, F have at least one lone pair of electrons when they form molecules > H of one molecule bonds w/ lone pair of F, N, or O atom of other molecule
What is the weakest bonding force (dispersion forces)?
Operates in all substances, only considered when only one (for non-polar molecules)
Arises out of constant movement of electrons in atoms and molecules
At one moment, more electrons at one side than other > momentarily polar > electrostatically interact w/ atoms or molecules > direction of instantaneous interactions are always changing > instantaneous dipole > net, but weak, force of attraction b/w all particle
Only force for noble gases in l and s states, and have low melt/boil temps (increase as atom size increases)
What is a semistructural formula (eg of butane)?
Eg of butane: CH3CH2CH2CH3