Shapes Of Molecules

Question 1

Describe the electron pair repulsion theory.

Answer 1

The shape of a molecule is determined by the electron pairs surrounding the central atom.

Only referring to outer shell.

Based on the fact that pairs of electrons repel all of the other electron pairs.

The electron pairs now move as far apart as possible to minimise this repulsion.

Question 2

If a central atom has two bonds or two bonding areas, what shape will it have?

Answer 2

It will have a linear shape with a 180 degree bond angle.

Question 3

If a central atom has three bonds or three bonding areas, what shape will it have?

Answer 3

It will have a trigonal shape with three 120 degree bonding angles.

It will be a planar molecule.
(Flat molecule)

Will be a flat molecule asking as central atom has no “lone pairs” of electrons.

So it will be called a “trigonal planar”

Question 4

What is a central atom, with four pairs of bonding electrons around it called?

Answer 4

A “Tetrahedral molecule”.
All of the bond angles are 109.5 degrees.

Question 5

What is a central atom, with five pairs of bonding electrons around it called?

Answer 5

Trigonal bipyramidal.

(Trigonal because the three atoms on the central plane are forming a triangle.)
(Bipyramidal because these form two pyramid shapes with the two other atoms, one above and one below)

Question 6

What is a central atom, with six pairs of bonding electrons around it called?

Answer 6

Octahedral shape