bonding Flashcards
explain the VSEPR theory
pairs of outer electrons arrange themselves as far away from each other to minimise repulsion
what is the name given to a molecule with 4 groups of electrons and what will the bond angle be?
eg CH4
tetrahedral
109.5
what is the name + bond angle of a molecule with four groups of electrons, one being a lone pair?
eg - NH3
trigonal pydramidal
107
water has four groups of electrons, 2 being lone pairs
name of shape and bond angle?
v shaped
104.5 because 2 lone pairs means more repulsion
name + bond angle of a molecule with three groups of electrons + no lone pairs?
trigonal planar
120
name and bond angle of a molecule where there are three groups of electrons and one lone pair?
bent / v-shaped
117.5
NOT THE SAME AS WATER BECAUSE WATER HAS 2 LONE PAIRS
name and bond angle of a molecule with 2 groups of electrons
linear
180
name and bond angle of molecule with five groups of electrons
trigonal bipyramidal
90 degrees on one side
120 on other
name and bond angle of molecule with 6 groups of electrons?
octahedral
90
list three types of IMF in ascending order of strength
van der waals
dipole - dipole
hydrogen
where can dipole dipole forces occur?
between molecules with permanent dipoles
molecules with polar bonds
the delta + and delta - regions attract each other to form a lattice structure
why does CO2 not have a dipole moment when it has more than one polar bond?
linear molecule so dipoles cancel out
why do vdW occur between all molecules?
all atoms/molecules positive and negative charges so are NEUTRAL overall
however they produce weak electrostatic attractions
helium has 2 protons and 2 neutrons and is neutral overall,
how can it have a permanent dipole?
at any one time, the electrons could be anywhere
the DISTRIBUTION OF CHARGE is changing at EVERY INSTANT
this means the atom has a dipole at THAT MOMENT
how does an induced dipole occur?
the temporary dipole in one atom then affects the distribution of electrons in nearby atoms to form an induced dipole
this atom is then attracted to the original atom for THAT INSTANT