Chapter 12.1 Shapes of Molecules

Question 1

What is the valence shell electron pair repulsion theory (VSEPR)?

Answer 1

A model used to predict the shape of molecules.

The basis of VESPR = valence electron pairs surrounding an atom repel each other and therefore they are an arrangement that minimises this repulsion thus determining the molecular shape

Question 2

What are the different shapes of molecules?

Answer 2

• linear (180°)
• trigonal planar (120°) (has three connecting from middle)
• Bent (104.45°) Eg water ( has the lone pair)
• Pyramidal (107.3°) (more than 4 bent) (has the lone pair)
• Tetrahedral (109.5°) (4 extending from the middle)

Question 3

How do electron pairs exist in a molecule?

Answer 3

Electron pairs can exist in COVALENT BONDS or as LONE PAIRS of electrons.

Lone pairs and covalent bonds repel each other

Lone pairs influence a molecule’s shape but are not considered part of the shape

Question 4

How are double and triple bonds treated in a covalent molecule according to VSEPR model

Answer 4

Double and triple bonds are treated in the same way as single bonds and lone pairs in the VSEPR model.