Define catenation. How will you explain the tendency for catenation decreases in the order C > Si > Ge > Sn > Pb?

Explain inert pair effect with reference to carbon family.
Or
Explain C and Si are tetravalent, but Ge, Sn and Pb show divalent.

Discuss the pattern of variation in the oxidation state of C to Pb.

Explain why silicon shows a higher covalency than carbon. 

Why silicon does not form an analogue of graphite?
Or
Why elemental silicon does not form graphite like structure as carbon does?

Select the member of group 14 that:
(i) forms the most acidic dioxide
(ii) is commonly found in +2 oxidation state
(iii) is used as semiconductor. 

[SiF₆]^2- is known whereas [SiCl₆]^2- or not. Give possible reasons. 

128.  are known to exist. Give possible reason.

What is allotropy? Enlist the various allotropic forms of carbon. 

Give the name of allotrope of carbon which:
(i) is the hardest substance known
(ii) is used by artists in pencils
(iii) has the property of adsorbing gases
(iv) is used for making electrodes
(v) is used for absorbing organic colouring matter.
(vi) is used in the manufacturing of boot polishes.