4.2 Resonance, Shapes & Giant Structures

This question is about the geometry of a number of common molecules.

Which molecule(s) has/ have tetrahedral structures with respect to the electron domain geometry?

[1]

What is the molecular geometry of CO₂?

[1]

Draw the 3D representation of ammonia, NH₃.

[1]

Estimate the H-O-H bond angle in water, H₂O, using VSEPR theory.

Explain your answer.

[3]

Suggest a way in which the bond angle in ammonia / NH₃ could become 109.5^o and explain your answer.

[3]

Ozone, O₃, is another simple molecule which has the following structure:

Estimate the O-O-O bond angle in ozone using VSEPR theory.

[1]

Explain why the actual bond lengths present in ozone are equal.

[2]

Carbon has three naturally occurring allotropes; diamond, graphite and buckminsterfullerene, C₆₀.

State how many atoms each carbon is directly bonded to in each of the allotropes, explaining any differences.

Describe the differences in the structures of the three allotropes of carbon.

Describe and explain the differences in electrical conductivity between the three allotropes of carbon.

Graphene can be made from graphite.

Describe a similarity and difference between these two structures.

[2]

Silicon and carbon are in the same group of the Periodic Table. They both form covalent bonds.

Both silicon and carbon form dioxides, but silicon dioxide has a melting point of 1710 ^oC whilst carbon dioxide has a melting point of -78 ^oC.

Explain this difference with reference to the structure and bonding present in each dioxide.

[4]

How many oxygen atoms are bonded to each carbon and to each silicon?

Explain how this links to the formula of each compound.

[3]

Predict the O-C-O and O-Si-O bond angles respectively in CO₂ and in SiO₂.

Predict and explain the solubility of both SiO₂ and CO₂ in water.