Fullerenes are the allotropes of carbon. Its structure is like a soccer ball.
They are prepared by heating graphite in electric arc in presence of inert gases such as helium or argon.

Because aluminium reacts with water and oxygen (dissolved in ) to form a thin layer of toxic aluminium oxide on the surface of utensils.
2Al(s) +O₂(g) + H₂O(l)\(\rightarrow\)Al₂O₃(s) + H₂(g)

Thallium and aluminium both the elements belong to group 13. Their general electronic configurations for the valence shell is ns²np¹ . Aluminium shows only +3 oxidation state. Like Al, thallium also shows +3 oxidation state in some compounds like Tl₂O₃, TlCl₃ , etc. Like aluminium, thallium also forms octahedral ions like [AlF₆]^3- and [TlF₆]^3- . Like group-I alkali metals, thallium shows +1 oxidation state due to inert pair effect in some compounds like TlCl, Tl₂O etc., like alkali metal hydroxides, TiOH is water soluble and its aqueous solution is strongly alkaline. Tl₂SO₄ also forms alums like alkali metal sulphates. Tl₂CO₃ is soluble in water like alkali metal carbonates.

The building block of zeolites is sodalite cage. The high porosity of zeolites is because of the sodalite cage packing in a three dimensional network of channels and cavities.

Sn⁴⁺ is more stable than Sn²⁺ thus Sn²⁺ have a great tendency to get converted into Sn⁴⁺ by losing two electrons hence, from the given compounds SnCl₂ is used as reducing agent.

Due to inert pair effect, Pb is more stable in +2 state than in +4 oxidation state. Therefore, lead (II) chloride does not react with Cl₂ to give lead (IV) chloride.

The main reasons for the existence of [SiF₆]^2- and non-existence of  [SiCl₆]^2- are as follows.
(i) Six large chloride ions cannot be accommodated around Si⁴⁺ due to limitation of its size. 
(ii) Interaction between lone pair of chloride ion and Si⁴⁺ is not very strong.

Since E^o values are more negative in case of AI, so it has higher tendency to form AI³⁺(aq) ions, whereas TI³⁺ is highly unstable in aqueous solution and acts as a good oxiding agent. It readily reduces to more stable TI⁺ ion AI³⁺ being stable, exists in this form and hence, AI is more electropositive as compared to TI.

BF₃ achieve it by the following ways
(i) Multiple bonding or \(p\pi -p\pi \) back bonding e.g BF₃ in which a lone pair of electron present in 2p-orbits of one of the fluorine atoms may be transferred to the vacant p-orbital on the bottom atom.
(ii) Formation of complexes in which electrons are received from a donor molecule,e.g F₃B\(\longleftarrow \)NH₃ .Boron compounds, thus behave as Lewis acids.

Boron and aliminium show an oxidation state of +3 only because they do not exhibit insert pair effect due to the absence of d or f-electrons. Elements from Ga to TI show two oxidation states, i.e +1 and +3.The tendency to show +1 oxidation state increases down the group due to the inability of ns² electrons of valence shell to participate in bonding which is called inert pair effect. Therefore TI⁺ is more stable than TI³⁺

Ultra pure elemental silicon is prepared by the reduction of highly pure silicon tetrachloride(SiCl₄) or silicon chloroform(SiHCl₃) with dihydrogen
\({ SiCl }_{ 4 }+2{ H }_{ 2 }(g)\longrightarrow Si+4HCl\)
\({ SiHCl }_{ 3 }+{ H }_{ 2 }\longrightarrow Si+3HCl\)
It can also be prepared by the pyrolysis of SiH₄
\({ SiH }_{ 4 }\longrightarrow Si+{ 2H }_{ 2 }\)
Ultra pure elemental silicon is used as a semiconductor.

\({ SiO }_{ 2 }+C\longrightarrow SiC+2CO\)
   silicon carbide Carbon or carborundum monoxide