shapes of molecules

valence shell electron pair repulsion theory

states that the outermost pairs of electrons in a molecule try to get as far away from eachother as possible to minimise the repulsion between these electrons in the outermost shell

types of electrons

bonding pairs

lone pairs

bonding pair

pairs of electrons in the outermost shell that are taking part in bonding, are shared between atoms

lone pairs

pairs of electrons in the outermost shell that do not take part in bonding, electrons are not shared

why do lone pairs have a greater repelling effect than bonding paors

found closer to the nucleus of the central atom, and dont have to be shared between two atoms

shape of a molecule consisting of two atoms

linear

linear bond angle

180°

bond angle of a v shaped atom

104.5°

how many bonding and lone pairs does a linear shape have

2 bonding pairs no lone pairs

how many bonding and lone pairs does a vshape have

2 bonding pairs, 2 lone pairs

how many bonding and lone pairs does triangular planer shape have

3bp 0lp

Trigonal planer bond angle

120

pyramidal shape bonding pairs/lp

3bp 1lp

Pyramidal shape bond angle

107°

why do some bond angles differ in the pyramidal shape

the increasing atomic radius of the central atom means that the shared pairs of electrons are further away from the central atom, and further away from each other

smaller force of repulsion between them and the bonds can come closer together

tetrahedral shape bonding pairs and lone pairs

4 bonding pairs, no lone pairs

bond angle of tetrahedral shape

109° (as far apart as possible)

what does one do when working out the shape of complex ions

add or subtract electrons from central atom depending on charge

two atoms in a molecule

linear

three atoms in a molecule with no lone pairs

linear

three stoms in a molecule has lone pairs

v shaped

four atoms in a molecule and no lone pairs

trigonal planer

four atoms in a molecule and has lone pairs

pyramidal

five atoms in a molecule

tetrahedral

three atoms in a molecule shape has to be either

linear or v shaped

four atoms in a molecule, shape has to be either

trigonal planer or pyramidal