Topic 2 Flashcards
what affects the strength of ionic bonding
smaller ionic radii means the ions pack closer together with stronger bonds
the higher the charge of the ion the stronger the bond
charge density = charge / size
the higher the charge density the stronger the bond
trend in ionic radii of isoelectronic ions
Decreases
proton number increases so it pulls nucleus closet
Dative covalent bonding
when it is energetically favourable for an atom to share the pair of electrons rather than one
the molecule formed will have a charge
reasons for shapes of simple molecules
Groups of electrons repel each other around the atom
They move as far apart from each other to minimise the electrostatic forces between each pair
what is electro negativity
the ability of an atom to attract the bonding electrons in a covalent bond
what are Van den waal forces
electron cloud wobbles creating a temporary dipole
the temporary dipoles can create induced temporary dipoles in other atoms
what are permanent dipole dipole attractions
the attraction between polar ends of a polar molecule
the dipoles are permanent
stronger than london forces but still weak
what is hydrogen bonding
occurs in molecules with (lone pair) N,O, F bonded to H
drawn in a straight line
hydrogen atom attracted to a very small highly electronegative atom
strongest intermolecular force
anomalous properties of water due to hydrogen bonding
unusually high melting and boiling points
ice is less dense than water because water molecules held apartin formation with space between them
viscosity is unusually high
why do boiling temperatures of alkanes increase with chain length
the more carbons the more van der waal forces present
more surface area and more electrons mean more van der waal forces
effect of branching on boiling temperatures of alkanes
branching decreases the surface area and makes it more compact
less vdw forces
what is volatility
the tendency of a substance to vaporise
reason for relatively low volatility of alcohol compared to alkanes of some carbon amount
alcohols have hydrogen bonding where alkanes do not
reason for trends in boiling temperature of hydrogen halides
the atomic radius increase to iodine so the surface area is larger which means increased vdw forces
solubility of metals
never soluble
