Chemistry- Chapter 6: Shape of Molecules and Intermolecular Forces

linear, 180 degrees, 2 electron pairs/regions, N/A bonded pairs, 0 lone pairs

trigonal planar, 120 degrees, 3 electron pairs/regions, 3 bonded pairs, 0 lone pairs

tetrahedral, 109.5 degrees, 4 electron pairs/regions, 4 bonded pairs, 0 lone pairs

pyramidal, 107 degrees, 4 electron pairs/regions, 3 bonded pairs, 1 lone pair

non-linear, 104.5 degrees, 4 electron pairs/regions, 2 bonded pairs, 2 lone pairs

octahedral, 90 degrees, 6 electron pairs/regions, 6 bonded pairs, 0 lone pairs

lone pair-lone pair, lone pair-bonded pair, bonded pair-bonded pair

a model that predicts the shapes of molecules and polyatomic ions and is dependent upon the arrangement of electron pairs around a central atom

the repulsion between pairs of electrons as electrons are negative

they arrange themselves in a way so that the repulsion between them is at a minimum

different shapes

the measure of attraction of bonded atom for the pair of electrons in a covalent bond or the ability of an atom in a covalent bond to attract electrons towards it

the pauling scale

the higher the Pauling electronegativity the greater the electronegativity

as the radius of an atom increases the lower electronegativity because the bonding pair of electrons become further from the nucleus and so are less attracted to its positive charge

distortion of electron cloud

the greater the electronegativity difference between atoms the greater the polarisation of the bond

the polarisation increases

the bonded pair of electrons is shared equally and there is a symmetrical electron cloud

when the 2 atoms in the covalent bond are identical and when the 2 atoms have the same electronegativity

the bonded pair of electrons is not shared equally and there is a distortion in the electron cloud (polarisation)

when the two atoms in the covalent bond have different electronegativities

it pulls the electrons towards itself

it leads to a partial negative charge on the most electronegative atom and a partial positive charge on the least electronegative atom

the dipoles may cancel out

induced dipole-dipole interactions (London Forces), permanent dipole-dipole interactions and hydrogen bonding

when there is an electrostatic force of attraction between the negative charge on one atom and the positive charge on the other atom

an uneven distribution of an electron cloud causing partial charges to develop on the atoms

between all atoms and molecules but are weak

only for an instant before they disappear and the whole process happens again with other atoms/molecules

1. the larger the instantaneous and induced dipoles and so the greater the interactions leading to stronger attractive forces between atoms

2. the stronger the forces the higher the higher the amount of energy required to seperate them therefore the higher the melting/boiling point

it increases because the size of the molecule increases, more electrons are involved which creates more instantaneous dipoles increasing the attractive forces and therefore more energy is needed to seperate them

an intermolecular force between the dipoles of neighbouring molecules that is permanent

stronger

they have higher boiling points than non-polar molecules as they have the strength of both the permanent dipoles and the London Forces (which are weaker)

low because only low energies are needed to the break the intermolecular forces

non-polar molecules are soluble in non-polar solvents and polar molecules are soluble in polar solvents

they are not conductive because there are no free electrons to carry the charge

a special type of permanent dipole-dipole interactions that only occurs between hydrogen and electronegative atoms (nitrogen, oxygen or fluorine)

between a lone pair of electrons on an electronegative atom with hydrogen

it is the strongest intermolecular force