When boric acid or borate salt is heated with ethyl alcohol in presence of conc. sulphuric acid, an ester, trialkylborane is formed. The vapour of this ester burns with a green edged flame and this reaction is used to identify the presence of borate.
\({ H }_{ 3 }{ BO }_{ 3 }+{ 3C }_{ 2 }{ H }_{ 2 }OH\overset { Conc }{ \underset { { H }_{ 2 }{ SO }_{ 4 } }{ \longrightarrow } } B\left( { OC }_{ 2 }{ H }_{ 5 } \right) +3{ H }_{ 2 }O\)

The mineral which contains silicon and oxygen in tetrahedral [SiO₄]^4- units linked together in different patterns are called silicates.

(i) Electronic Configuration: \(1 s^{2} 2 s^{2} 2 p^{3}\)
(ii) Nitrogen does not form pentahalide although it exhibit +5 oxidation state. Due to absence of d-orbitals Nitrogen cannot extend its valency beyond four. It cannot undergoes sp³ d hybridization and hence cannot form pentahalides.

CO acts as a strong reducing agent.
Example: 3CO + Fe₂O₃ \(\longrightarrow \)  2Fe + 3CO₂
It reduces metallic. oxides into metals.

(i) Zeolites are three-dimensional crystalline solids containing Al, Si and O in their regular three dimensional framework.
(ii) They are hydrated sodium alumino silicates with general formula Na₂O(AI₂O₃).·x(SiO₂)·yH₂O
(x = 2 to 10; y = 2 to 6).
(iii) Zeolites have porous structure in which the monovalent sodium ions and water molecules are loosely held.
(iv) The Si and Al atoms are tetrahedrally coordinated with each other through shared oxygen atoms.
(v) Zeolites are similar to clay minerals but they differ in their crystalline structure.
(vi) Zeolites have a three dimensional crystalline structure looks like a honeycomb consisting of a network of interconnected tunnels and cages.
(vii) Water molecules moves freely in and out of these pores but the zeolite framework remains rigid
(viii) Another special aspect of this structure is that the pore/channel sizes are nearly uniform, allowing the crystal to act as a molecular sieve.

When boric acid or borate salt is heated with ethyl alcohol in presence of conc. sulphuric acid, an ester, trialkylboranes is formed.
The vapour of this ester burns with a green edged flame
This reaction is used to identify the presence of triethyl borate.
\({ H }_{ 3 }{ BO }_{ 3 }+{ 3C }_{ 2 }{ H }_{ 5 }OH\overset { Conc }{ \underset { { H }_{ 2 }{ SO }_{ 4 } }{ \longrightarrow } } B\left( { OC }_{ 2 }{ H }_{ 5 } \right)_3 +3{ H }_{ 2 }O\)
                       Ethyl borate
                        (Green edged flame)

(i) In diborane two BH₂ units are linked by two bridged hydrogens.
(ii) It has eight B-H bonds.
(iii) Diborane has only 12 valance electrons.
(iv) The four terminal B-H- bonds is "2c - 2e" bond (two centre - two electron bond.)
(v) Two three centred B - H - B bonds two electrons each. "(3c - 2e)"
(vi) In diborane, the boron is "sp³" hybridised
(vii) Three of the four "sp³" hydridised orbitals contains single electron and the fourth orbital is empty.

The reaction of CO with hydrogen at a pressure of less than 50 atm using metal catalysts at 500 - 700 K yields saturated and unsaturated hydrocarbons.
\(nCO+(2n+1){ H_2 }\longrightarrow C_{ n }{ H }_{ (2n+2) }+{ nH }_{ 2 }O\)
\(nCO+2n{ H }_{ 2 }\longrightarrow { C }_{ n }{ H }_{ 2n }+{ nH }_{ 2 }O\)

Catenation is an ability of an element to form chain of atoms.
The conditions for catenation.
(a) The valency of element is greater than or equal to two.
(b) Element should have an ability to bond with itself
(c) The self bond must be as strong as Its bond with other elements
(d) Kinetic inertness of catenated compound towards other molecules.
(e) Carbon possesses all the above properties and forms a wide range of compounds with itself and with other elements such as H, O, N, S and halogens.

In p-block elements, the first member of each group differs from the other elements of the corresponding group. The following factors are responsible for this anomalous behaviour
(i) Small size of the first member.
(ii) High ionisation enthalpy and high electronegativity.
(iii) Absence of d-orbitals in their valance shell.

When boric acid or borate salt is heated with ethyl alcohol in presence of conc. sulphuric acid, an ester, triethyl borate is formed. The vapour of this ester burns with a green edged flame and this reaction is used to identify the presence of borate.
H₃BO₃ + 2C₂H₅OH \(\frac{\text { Conc. }}{ H_2SO_4 } \longrightarrow \) 2B(OC₂H₅)₃ + 3H₂O

\({ }_{13} \mathrm{Al}-[\mathrm{Ne}] 3 \mathrm{~s}^{2} 3 \mathrm{p}^{1}\) and \({ }_{81} \mathrm{Tl}-[\mathrm{Xe}] 6 \mathrm{~s}^{2} 4 \mathrm{f}^{14} 5 \mathrm{~d}^{10} 6 \mathrm{p}^{1}.\)
On going down the group, d and f - electrodes are present. They have poor shielding effect. Compound to s and p - electrodes.

Aqueous HF reacts with silica and silicates of glass.
\(\mathrm{SiO}_{2}+4 \mathrm{HF} \rightarrow \mathrm{SiF}_{4}+2 \mathrm{H}_{2} \mathrm{O}\) 
\(\mathrm{Na}_{2} \mathrm{SiO}_{3}+6 \mathrm{HF} \rightarrow \mathrm{Na}_{2} \mathrm{SiF}_{6}+3 \mathrm{H}_{2} \mathrm{O}\)
Hence SiCl₄ or \(\mathrm{Na}_{2} \mathrm{SiF}_{6}\) is formed as above.

When treated with excess ammonia at low temperatures diborane gives diborane diammoniate. On heating at higher temperatures it gives borazole
\(3 \mathrm{~B}_{2} \mathrm{H}_{6}+6 \mathrm{NH}_{3} \stackrel{-153 \mathrm{~K}}{\longrightarrow} 3 \mathrm{~B}_{2} \mathrm{H}_{6} 2 \mathrm{NH}_{3}(\mathrm{or}) 3\left[\mathrm{BH}_{2}\left(\mathrm{NH}_{3}\right)_{2}\right]^{+}\left[\mathrm{BH}_{4}\right]^-\)

1. Al⁺³ is more stable than Al⁺¹ while Tl⁺¹ is more stable than Tl⁺³.
2.  Aluminium (III) chloride is stable whereas thallium (III) chloride is highly unstable and disproportionates to thallium (I) chloride and chlorine gas.
3. This shows that in thallium the stable lower oxidation state corresponds to the loss of np electrons only and not ns electrons.
4. Thus in heavier post-transition metals, the outer s electrons (ns) have a tendency to remain inert and show reluctance to take part in the bonding which is known as inert pair effect.
5. This effect is also observed in groups 14,15 and 16.

It decomposes to give \(\mathrm{K}_{2} \mathrm{SO}_{4} \cdot \mathrm{Al}_{2} \mathrm{O}_{3}\) and SO₃.

1. These are silicates containing \(\left[\mathrm{Si}_{4} \mathrm{O}_{11}\right]_{\mathrm{n}}^{6 n-}\) ions.
2. In these silicates there are two different types of tetrahedra
(i) Those sharing 3 vertices.
(ii) Those sharing only 2 vertices. Ex: Asbestos

(i) In p-block elements, the first member of each group differs from the other elements of the corresponding group. The following factors are responsible for this anomalous behaviour.
(ii) Small size of the first member.
(iii) High ionisation enthalpy and high electronegativity.
(iv) Absence of d-orbitals in their valence shell.

A hydride of 2^nd period alkali metal (A) is lithium hydride (LiH).
Lithium hydride (A) reacts with diborane (B) to give lithium borohydride (C) which is acts as a reducing agent.
B₂H₆ + 2 LiH \(\xrightarrow[]{ether}\) 2 LiBH₄
[Diborane (B)]   [Lithium hydride (A)]  [Lithium borohydride (C)]
Result:

Compound	Formula	Name
A	LiH	Lithium hydride
B	B2H6	Diborane
C	LiBH4	Lithium borohydride

Fusion of urea with B(OH)_3' in an atmosphere of ammonia at 800 - 1200 K gives boron nitride.
B(OH)₃ + NH₃ \(\overset { \Delta }{ \longrightarrow } \) BN+ 3H₂O

(i) Silicones are used for low temperature lubrication and in vacuum pumps, high temperature oil baths etc.
(ii) They are used for making water proofing clothes.
(iii) They are used as insulting material in electrical motor and other appliances.
(iv) They are mixed with paints and enamels to make them resistant towards high temperature, sunlight, dampness and chemicals.

(i) Borax is used for the identification of coloured metal ions.
(ii) In the manufacture optical and borosilicate glass, enamels and glazes for pottery.
(iii) It is also used as a flux in metallurgy.
(iv) It acts as a good preservative.

(i) In diborane two BH₂ units are linked by two bridged hydrogens.
(ii) It has eight B-H bonds.
(iii) Diborane has only 12 valance electrons.
(iv) The four terminal B-H- bonds is 2c - 2e bond (two centre - two electron bond.)
(v) Two three centred B - H - B bonds two electrons each. (3c - 2e).
(vi) In diborane, the boron is sp³ hybridised
(vii) Three of the four sp³ hydridised orbitals contains single electron and the fourth orbital is empty.