Shapes Of Molecules

Question 1

Molecular shape

Answer 1

The molecular shape depends on the number of pairs of electrons in the outer shell of the central atom

Question 2

Electron pairs repel each other

Answer 2

Lone pair of electrons repel more than bonding pairs

Therefore the greatest angles are between lone pairs of electrons, and bond angles between bonding pairs often reduced because they’re being pushed together by lone pair repulsion

Therefore shape of a molecule depends on the type of electron pairs surrounding central atom as well as the number. This is known as the electron pair repulsion theory

Question 3

Predicting shapes of molecules by using electron pairs

Answer 3

You first find the central atom

work out the number of electrons on the outer shell of the central atom

the molecular formula tells you how many atoms the central atom is bonded to

therefore you can look at how many electrons are shared with the central atom

add up the electrons and divide by 2 to find out the number of electron of the central atom

compare the number of electron pairs of the number bonds to find out the number of lone pairs

you could then use a number of electron pairs and the number of lone pairs and bonding centres around central atom to work out the shape of a molecule