Hack tech fact

 Allotropy of Group 15 elements : All the elements (except Bi) of this group show allotropy. Solid nitrogen exists in two allotropic forms, i.e., Alfa-nitrogen with cubic crystalline structure and Bita-nitrogen with hexagonal crystalline structure.  Phosphorus exists in a number of allotropic forms, such as white,red,scarlet, Alfa-black, Bita-black and violet. Arsenic exists in three allotropic form, i.e., grey, yellow and black. Antimony exists in three allotropic forms, i.e., yellow,black and explosive.

Uses of copper: Copper can be used a number of purposes. 1- For manufacturing electric articles,wires, etc . 2- For the manufacturing alloy and silver coins. 3- In the copper plating and electrotyping . 4- For covering the bottom of wooden ships. 5- For making utensils, calorimeters, and vacuum pans.

 Occurrence Nitrogen : Nitrogen was discovered by Daniel Rutherford in the year 1772. As it was found from nitra, it's name was given nitrogen. It exists in diatomic state and thus it is named as dinitrogen. Occurrence:                                    it occurs in the nature both in the free and combined state. Air contains 75% by weight and 80% by volume of nitrogen. In combined state it is mostly found as Chile salt pertre(NaNO³), Indian salt petre (KNO³)  ammonium salts, etc. It is found in the plants and animals as amino acids and proteins.

Ammonia- Ammonia is present in traces  in atmosphere. It is also found in soil where nitrogenous matter, such as urea decomposes to ammonia. This is also formed by the bacteria decomposition of nitrogenous matter of plants and animals. It is also found in Jupiter and Saturn in abundance.                       Ammonia is one of the most important compounds of nitrogen. It was first prepared by Priestly in the year 1774.

 Physical properties of dinitrogen: 1- It is a colorless , odour less, tasteless and non toxic gas.  2- It is partially soluble in water but it's solubility in water increases by the rise of pressure. 3- It is neither combustible nor a supporter of the combustion. 4- It has low boiling point (77.2k) and freezing point (63.2k). 5- It is adsorbed by activated charcoal.

Uses of Dinitrogen -  It is used-  1- For the manufacturer of the nitric acid, ammonia, nitrolim, etc. 2- To provide inert atmosphere in certain metallurgical operations. 3- For feeling electric bulbs. 4- Liquid nitrogen is used as refrigerant to preserve biological materials, food materials. 5- Nitrogen gas filled thermometers are used for measuring high temperature. 6- As cryogen in cryosurgery i.e., used in cooling a localized area of skin prior to remove wart or other unwanted or pathogenic tissues. 

Tests of ammonia: 1- It is detected by it's characteristics pungent odour. 2- It forms a dense white fumes of ammonium chloride with a drop of conc. HCL. 3- It gives a deep blue colour with CuSO⁴ solution. 4- It turns moist red litmus paper blue and moist turmeric paper brown. 5- It forms a reddish brown ppt with Nessler reagent.

Fuming  Nitric Acid When NO² gas is dissolved in conc. Nitric Acid, it forms fuming nitric acid. It is also obtained by distilling concerned nitric acid with a little starch. Nitric acid is reduced to No² by starch which dissolves in the remaining acid to from fuming nitric acid. This acid is yellow in colour due to the presence of NO² in it. It is a powerful oxidising agent and nitrating agent as compared to conc. HNO³.

 Uses of Nitric Acid It is used 1- In the manufacturer of fertilizers like calcium ammonium nitrate (CAN). 2- In the preparation of dyes , medicine , perfumes etc. 3- In the purification of silver and gold in the form of aquaregia.  4- For the manufacturer of explosive substance like TNT, nitroglycerin, picric acid, etc. 5- In the manufacturer of artificial silk. 6- As a laboratory reagent. 7- In the manufacturer of the sulphuric acid. 8- For the nitration of organic compounds.

A little about Group - 16 elements: The elements, oxygen (O), sulphur (S), selenium (Se), tellurium (Te) and polonium (Po)  constitute group 16 or VIA of the periodic table. These elements are commonly known as Chalcogens or ore forming elements because the ore of many metals occur as oxides and sulphides. As oxygen is the first member of this group, these are commonly known as oxygen family members.  

Siemens Ozoniser:  This Ozoniser consist of two co-axial glass tubes fused together at one end. The outer side of the outer glass tube and the inner side of the inner glass tube are finally coated with tin foils as shown in the figure given below.  (Siemens Ozoniser)->2                                                     (Siemens Ozoniser)->1 These tin foil are connected  to the induction coil for supply of silent electric discharge. Pure and dry oxygen gas is passed into the apparatus through annular space. The gas is then subjected to the action of silent electric discharge where oxygen gets converted into ozone. The ozonised oxygen then comes out  of the apparatus through the outlet of the Ozoniser. (Siemens Ozoniser)->2

 Laboratory methods of preparation - O zone is prepared by passing silent electric discharge through dry, pure and cold oxygen.     3O²  ---->   2O³, ∆H= + 68 Kcal.        <----  Since the formation of ozone is endothermic, it requires high energy which is obtained by silent electric discharge. The silent electric discharge act like U.V. light and decompose ozone molecules into oxygen atoms which then recombines with the undissociated  oxygen molecules to form Ozone. This mixture obtained is called ozonised oxygen and the apparatus used to prepare ozone is known as ozoniser . Mainly there are two types of Ozonisers and known ,  1- Siemens Ozoniser  2- Brodie's Ozoniser       

Ozone or Trioxygen (0³) -   Ozone is found abundantly in the atmosphere at higher altitudes. It is formed there by the action of the oxygen under the action of ultra - violet light of sun. Ozone absorbs the ultraviolet light to form oxygen again. UV rays are harmful to living organisms. Thus, ozone layer acts as a screen and prevent the harmful  UV radiations to reach the earth's surface. It is also found near the sea side or big lakes where it is formed by the slow evaporation of water.

 Some methods of preparation of Ozone- By the action of fluorine on water: - Fluorine reacts with water at a very low temperature to give a mixture of ozonised oxygen               3F²+3H²O--->6HF+O³ By the action of u.v. rays on oxygen:  - Oxygen is converted to ozone by action of UV radiation. By the action of UV rays, the O² break into atomic atomic oxygen which then combines with oxygen which then then combines with oxygen (O²) to from ozone.               O² --UV rays--> O+O               O²+O ------------>   O³ By the electrolysis of acidulated water:  - The electrolysis of acidified water using Pt electrodes and high current density liberated at  anode may combine with molecular oxygen to form ozone.

Uses of Dioxygen- It is used.  1- as an important constituent of rock fuels. 2- along with He or CO² for artificial respiration. 3- liquid oxygen mixed with finely divided carbon is used like a dynamite in coal mining.  4- As an oxidising agent in different reactions. 5- For the preparation of oxy - hydrogen or oxy - acetylene flames employed for cutting and welding of metals. 6- in the manufacturer of a large number of compounds such as phenol, sulphuric acid , nitric acid, Chlorine etc.

Uses of ozone-  It is used : 1- As a bleaching agent for oil, ivory,starch and delicate materials.  2- As a germicide and disinfect. For sterilizing water and for purifying air in crowded place like  underground railways tunnels , mines and cinema halls. 3-  As an oxidising agent in the chemical reactions . 4- for the manufacture of artificial silk, synthetic camphor, etc.  5- for detaching the position of carbon-carbon  double bond in the unsaturated compounds.  6- for the manufacturer of the Potassium permanganate. 7- for destroying foul smells of cold storage rooms kitchen or big hotels, etc.

Physical properties of ozone- 1- It is a pale blue gas at ordinary temperature and liquefies at 112.4° and solidifies at - 249.7°C to violet black Crystals. 2- It has a characteristics strong fishy smell and is poisonous.  3- It is slightly soluble in water but is more soluble in terpentine oil, glacial acetic acid or carbon tetrachloride. 4- It is heavier than air.

H²S acts only as reducing agent while SO² can act  as reducing as well as oxidising agent. Ans- S in H²S is in the oxidation state of -2, which is the minimum oxidation state of S. It can only increase it's oxidation state and thus act as a reducing agent. On the other hand, the oxidation state of (S) in So² is +4 which lies in between 2 and +6. It can both increase (reducing agent) and decrease (oxidising agent) it's oxidation number . Therefore, it can act both as oxidising as well as reducing agent.

Nature of halogen bond - Halogen form ionic compounds with metals because of their highly electronegative value. They form covalent compound with non metals or among themselves. Because of highest electronegativity of F it always from ionic compounds with other elements. 

Colour -   Halogens are coloured. F² Is light yellow, Cl² is greenish yellow, Br² is reddish brown and iodine is deep violet. The colour of the halogens is due to the fact that their molecules absorb visible light which excite their electrons to higher energy states. Again the difference in the colour of the halogens can be attributed to their size which is tunn may be due to their difference in their ionization potential. As IP decrease, the excitation energy decrease and thus colour changes from high energy radiation to low energy radiation. The colour of the F² is light yellow which is the complementary colour of the violet because it absorb high energy radiation  i.e., violet light. I² is violet, which is the complementary colour of the yellow because it absorb low energy radiation i.e yellow light.

About p- Block Elements (Group 17 Elements- The non-metallic elements fluorine, Bromine, iodine and astatine constitute a group VIIA or 17 of the periodic table. These are collectively known as the halogens as their salts are present in sea water (Greek:halo=sea salt, genes= producing). They have one electron less than the nearest noble gas elements, for which they exist as non-metals. These are highly electronegative elements and thus are very reactive in nature. Fluorine, the first member of the elements is the most reactive element because of its highest electronegativity value. Astatine the last member of the halogen family is a radioactive element which has very short life period.

 Non metallic character- The members of halogen family are non metallic in character. This is because of their Ionisation energies. On moving down the group, the value of Ionisation energy decrease. Therefore, iodine show some metallic characters.

Melting points and boiling points - Due to small size, the halogen have low melting points and boiling in their respective periods. However on moving down the group, the melting points and boiling points gradually increase. It is because of increase of magnitude of van der waals forces of attraction due to the increase in the molecular sizes. 

Electronegativity- The electronegativity value of the halogen family members are higher than those of corresponding elements if oxygen family members due to the small size and high nuclear charge of halogen family members. The electronegativity decrease on moving down the group due to increase of atomic size. F has highest electronegative value than any other elements.

Electron Affinity (Electron gain Enthalpy) - Halogens possess maximum electron affinities ( -ve electron enthalpies) in their respective periods, because of their small size and high effective nuclear charge. They require only one electron to complete their octct. Because of compact size, electron affinity of F is less than Cl. However, electron affinity decrease down the group from Cl to I. This is again due to increase in size of atoms.

 Ionisation energy (Ionisation enthalpy)- Ionisation energy of all the halogens are very high because of small size and high effective nuclear charge of halogen atoms in  their respective period. However, Ionisation energy decrease on Moving down the group from fluorine to iodine which is due to increase in the size of the atom. Thus due to the low Ionisation energy of iodine, it is capable of forming I+ ion in it's compounds. Therefore, due to low IE of iodine it shows electro +ve or metallic character.

Atomic and ionic radii of Halogens-  Atomic and ionic radii of halogens are the smallest in the respective periods. This is due to maximum effective nuclear charge of the halogens in their respective periods. However, these value regularly increase on Moving down the group from fluorine to iodine due to the addition of new shells in each successive element.  

Physical state of Halogens->  Halogens are non polar molecules. On moving down the group the van der waals forces of attraction increases due to the increase of the atomic sizes. As a result of which,the state of the molecules increases from gaseous state to solid state. Therefore, F²,Cl² are gases, Br² is liquid and I² is a solid at room temperature. Further on account of weak van der walls forces , the halogens are volatile in nature. 

Bromine- It occurs to an extent of 2.5×10 -⁴% in earth crust as bromides. The main source of bromine are. -> 1- sea water which contains bromides such as NaBr,KBr,MgBr² etc are found in small amounts. 2- NaBr,MgBr² etc are found in small amounts in mineral springs and salt lakes. 3- Bromogyramite - a mineral of AgBr.

Iodine-                                                             It occurs to an extent of 8×10 -5   % in earth crust as iodide and iodates. Main source of iodine are: 1- Certain deep sea weeds (Laminaria species). These plants contain about 0.5% iodide in their ashes in the form of iodide (Know as kelp)  2- Crude chile salt petre (caliche) contains about 0.2% of NaIO³.(Sodium iodate)  3- The ores of lead and dolomite contain traces of sodium potassium and magnesium iodide.  4- Oil-well brines and sea water also contain very very small amount of iodides.