2.2.9 Shapes of Molecules and Ions

Question 1

What is electron pair repulsion theory?

Answer 1

The shape of a molecule or ion is determined by the number of electron pairs in the outer shell surrounding the central atom. These pairs can be bonding or lone pairs. As electrons all have negative charge, each electron pair repels the other electron pairs. The shape adopted will be the shape that allows all the pairs of electrons to be as far apart as possible.

Question 2

What is the name and bond angle of a molecule with one bonded electron pair?

Answer 2

Linear, 180º

Question 3

What is the name and bond angle of a molecule with two bonded electron pairs?

Answer 3

Linear, 180º

Question 4

What is the name and bond angle of a molecule with three bonded electron pairs?

Answer 4

Trigonal planar, 120º

Question 5

What is the name and bond angle of a molecule with four bonded electron pairs?

Answer 5

Tetrahedral, 109.5º

Question 6

What is the name and bond angle of a molecule with five bonded electron pairs?

Answer 6

Trigonal bipyramid, 90º / 120º

Question 7

What is the name and bond angle of a molecule with six bonded electron pairs?

Answer 7

Octahedral, 90º

Question 8

What are the relative strengths of repulsion?

Answer 8

lone pair/lone pair > bonded pair/lone pair > bonded pair/bonded pair