Shapes of simple molecules and ions

Question 1

Name three factors that determine the shape of the molecule

Answer 1

• The number of electron pairs around a central atom

-The number of bonding pairs of electrons

• The number of lone pairs of electrons

Question 2

Describe the strengths of repulsion between lone pairs and bonding oairs

Answer 2

Repulsion between two lone pairs is greater than

Repulsion between a lone pair and a bonding pair which is greater than

Repulsion between two bonding pairs

Question 3

Describe the three lines used to draw bonds

Answer 3

Dotted line - going away from you
Wedge - coming towards you
Line - planar to you

Question 4

What steps are involeved to work out the shape of a molecule

Answer 4

• Dot and cross diagram
• Count total of BP and LP
• Work out the shape (amend for lone pairs)

Question 5

What is the RULE with shapes of molecules

Answer 5

Molecules adopt the shape that minimizes repulsion

Question 6

Describe the shape and angle(s) of a molecule with 2BP and 0LP (e.g Beryllium Chloride)

Answer 6

Shape is Linear
Angle = 180 degrees
Bonding pairs repel equally

Question 7

Describe the shape and angle(s) of a molecule with 3BP and 0LP (Boron Trifluoride)

Answer 7

Shape is trigonal planar
Angle is 120 degrees
Three bonding pairs repel equally

Question 8

Describe the shape and angle(s) of a molecule with 4BP and 0LP (e.g Methane)

Answer 8

Shape is tetrahedral
Angle is 109.5
Four bonding pairs repel equally

Question 9

Describe the shape and angle(s) of a molecule with 5BP and 0LP (e.g Phosphorous Pentachloride)

Answer 9

Shape is trigonal bipyramidal
Angle is 120/90 degrees

Question 10

Describe the shape and angle(s) of a molecule with 6BP and 0LP (e.g Sulfur Hexafluoride)

Answer 10

Shape is octahedral
Angle is 90 degrees