Chapter 6- Shapes of Molecules and Intermolecular forces

Question 1

The electron-pair repulsion theory is a model used in chemistry for explining and predicting the shapes of molecules and polyatomic ions. Explain it:

Answer 1

• The electron pairs surrounding a central atom determine the shape of the molecule or ion
• The electron pairs repel one another so that they are arranged as far as possible
• The arragement of electron pairs minimises repulsion and thus holds the bonded atoms in a definite shape
• Different numbers of electron pairs result in different shapes

Question 2

which type of bond in electrons is more repulsive?

Answer 2

Bonded-pair/bonded-pair < bonded-pair/lone-pair < lone-pair/lone-pair

Question 3

Shape of CH4, NH3, H20:

Answer 3

CH4 NH3 H2O
bonded pairs| 4 3 2
lone pairs | 0 1 2
Name of | tetrahedral pyramidal non-linear
shape
Angle | 109.5º 107º 104.5º