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Because of small size and high sum of first three ionization enthalpies (H₁ + H₂ + H₃), B (boron) forms only covalent compounds.

Concentrated nitric acid is a strong oxidizing agent. It is used oxidizing most metals. The products of oxidation depend on the temperature, concentration of the acid, and also on the material undergoing oxidation.

3Cu + 8HNO₃ (dil) → 3Cu(NO₃)₂ + 2NO + 4H₂O

Cu + 4HNO₃ (conc. ) → Cu(NO₃)₂ + 2NO₂ + 2H₂O

(i) Cu + 4HNO₃ (conc. ) → Cu(NO₃)₂ + 2NO₂ + 2H₂O

(ii) Zn + 4HNO₃ (conc. ) → Zn(NO₃)₂ + 2H₂O + 2NO₂

(iii) C + 48HNO₃ (conc. ) → 8H₂SO₄ + 48NO₂ + 16H₂O

(iv) S₈ + 48HNO₃ (conc. ) → 8H₂SO₄ + 48NO₂ + 16H₂O

(v) P₄ + 20HNO₃ (conc. ) → 4H₃PO₄ + 20NO₂ + 4H₂O

(i) On a large scale, it is prepared mainly by Ostwald’s process. This method is based upon catalytic oxidation of NH₃ by atmospheric oxygen.

(ii) 4NH₃(g) + 5NO₂(g) \(\underset{9 bar}{\stackrel{Pt,500K}{\rightarrow}} \) 4NO(g) + 6H₂O(l)

2NO(g) + O₂ → 2NO₂ (g)

3NO₂ (g) + H₂O(l) → 2HNO₃ (aq) + NO(g)

(iii) 68% by mass,

(iv) (a) It is used in the manufacture fertilizers, explosives.

(b) It is used as lab regent.

(i) In pentahalides, the oxidation state is +5 and in trihalides, the oxidation state is +3. Since the metal ion with a high charge has more polarizing power, pentahalides are more covalent than trihalides.

(ii) As we move down a group, the atomic size increase and the stability of the hydrides of group 15 elements decrease. Since the stability of hydrides decrease on moving from NH₃ to BiH₃, the reducing on moving from NH₃ to BiH₃.

(iii) Nitrogen has a small size due to which the lone pair of electrons is concentrated in a small region. This means that the charge density per unit volume is high.

On moving down a group, the size of the central atom increases and the charge gets distributed over a large area decreasing the electron density. Hence, the electron donating capacity decreases on moving down the group.

(iv) Nitrogen owing to its small has a tendency to from pπ− pπ multiple bonds with itself. Nitrogen thus forms a very stable diatomic molecule, N₂. On moving down a group, the tendency to form pπ − pπ bonds decrease (because of the large size of heavier elements). Therefore, phosphorus (like other heavier metals) exists in the P₄ state.

(v) N (unlike P) lacks the d-orbital. This restricts nitrogen to expand its coordination number beyond four. Hence, R₃N = O does not exist.

Water gas is the mixture of CO and H₂ gas.

(c) (i) and (iii)

Phosphine is used for producing smoke screen as it gives large smoke. In a ship, a pierced container with a mixture of calcium carbide and calcium phosphide, liberates phosphine and acetylene when thrown into sea. The liberated phosphine catches fire and ignites acetylene. These burning gases serves as a signal to the approaching ships. This is known as Holmes signal.

(b) Metaphosphoric acid

1. The red phosphorus is used in the match boxes. 

2. It is also used for the production of certain alloys such as phosphor bronze.

The most common allotropic forms of phosphorous 

1. white phosphorous 

2. Red phosphorous 

3. Black phosphorous

1. I > II > III

• The seventh element of the periodic table between carbon and oxygen is Nitrogen.
• It’s an important part of amino acids.
• Around eighty percent of the Earth’s atmosphere comprises nitrogen gas.
• It has no colour, mostly diatomic non metal gas along with odourless and colourless in nature.
• Since it has five electrons in its outer shell, most of its compounds are trivalent.
• It is a constituent of all living tissues. Since it is a component of DNA and part of a genetic code, it is an essential element of life.
• It is found in nitrates and nitrites in soil and water.
• All these substances are part of the nitrogen cycle and interconnected. Industrial companies emit nitrogen extensively, increasing nitrite and nitrate content in the ground and water, being the consequence of reactions in the nitrogen cycle.

The uses of chlorine is:

1. Purification of drinking water 

2. Bleaching of cotton textiles, paper and rayon 

3. It is used in extraction of gold and platinum

1. If chlorine reacts with excess ammonia, it gives nitrogen and ammonium chloride. 

8NH₃ + 3Cl₂ → N₂ + 6NH₄Cl 

2. If ammonia reacts with excess chlorine, it gives nitrogen trichloride and ammonium chloride. 

4NH₂ + 3Cl₂ → NCl₂ + 3NH₄Cl

P₄O₆ reacts with cold water to give H₃PO₃

Uses of silicones: 

1. Silicones are used for low temperature lubrication and in vacuum pumps, high temperature oil baths etc. 

2. They are used for making water proofing clothes.

3. They are used as insulting material in electrical motor and other appliances 

4. They are mixed with paints and enamels to make them resistant towards high temperature, sunlight, dampness and chemicals.

(d) Fischer tropsch Synthesis – HCOOH

In AlCl₃ , Al in electron deficient it needs two electrons to complete octet so it act as lewis acid. AlCl₃ usually exist as a dimer to achieve octet by bridged Cl atom electron deficient compounds are lewis acids.

(i) Due to the electronegativity differences between CI (3.16) and AI (1.61), CI makes a good electron-withdrawing group in AlCl₃.

Furthermore, AI must access both its 2s and its three 2p orbitals to bond, so it uses sp³ hybridisation (one 2s and three 2p orbitals), giving it four bonding orbitals (one of which is empty as AlCl₃ ). This allows it to form a fourth bond and acquire a tetrahedral structure as [AlCl₄⁻]⁻. With one empty orbital and three electron- withdrawing Cl atoms attached, the compound is thus an electron-acceptor at the Al center. By definition, that is a Lewis acid.

(ii) Silicones are aryl or alkyl substituted silicon chloride R_n SiCl (4 − n). The non- polar alkyl groups are water repelling, so they are used in water proofing materials.

Silicones are used for making water-proof papers by coating them with a thin layer of silicones.

Pyrosilicates contain Si₂O_7⁶⁻ anion.

Unlike NH₃, PH₃ molecules are not associated through hydrogen bonding in liquid state. That is why the boiling point of PH₃ is lower than NH₃.

This is because in PCl₃ phosphorus is in the intermediate oxidising state of -3.

1. As reducing agent : The following reactions support the reducing behaviour of PCl₃.

• PCl₃ + SO₂Cl₂ → PCl₅ + SO₂
• PCl₃ + SO₃ → POCl₃+ SO₂

 2. As an oxidising agent : It oxidises metals to their respective chlorides.

• 12Ag + 4PCl₃ → 12AgCl + P₄
• 6Na + PCl₃ → 3NaCl + Na₃P 

(a) Diborane – welding torches

1. Boric acid 

2. two dimensional layered 

3. [BO₃]^3-

4. borones 

5. trimethylborate 

6. eight 

7. sp³

8. Borazine 

9. planar 

10. hygroscopic

4. Only I and II are correct.

(a) phosphorescence

Euchlorine is a mixture of Cl₂ + ClO₂

2. CaCl₂  and Ca (ClO₃)

With H3 PO₄. X and Y are I₂HI.

Compound used in photography is AgNO₃

Oxidation state of N m FINO₃ is +5

1. OF₂

+2 + 2(x) = 0

+2 = -2x

2x = -2

x = -1 

2. O₂F₂

2(+1) + 2x = 0

2x = – 2

x = – 1

3. Cl₂O₃ 

2(x) + 3(-2) =0

2x = +6

x = +3 

4. I₂O₄ 

2(x) + 4(-2) =0

2x = +8

x = +4

The dielectric constant of ammonia is (K) 10^-30

Liq N₂ is used in cryosurgery

Fullerenes are the allotropes of carbon.

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. 

1. Small size of the first member. 

2. High ionisation enthalpy and high electronegativity. 

3. Absence of d-orbitals in their valance shell. 

The first member of the group-13, boron is a metalloid while others are reactive metals. Moreover, boron shows diagonal relationship with silicon of group -14. The oxides of boron and silicon are similar in their acidic nature.