But Al does not exist in different forms. The melting and boiling point of boron are much higher than that of Al. Boron forms only covalent compounds whereas Al forms even some ionic compounds.
The hydroxides and oxides of boron are acidic in nature whereas those of aluminium are amphoteric. The trihalides of boron exist as monomers. On the other hand, aluminium halides exist as dimers. The hydrides of boron are quite stable while those of aluminium are unstable. These do not form cations.
Both exist in amorphous as well as crystalline forms. The hydrides of Boron and Silicon are quite stable. Numerous volatile hydrides are also known which catch fire on exposure to air and are easily hydrolyzed. Both elements are semiconductors. Al, Ga. Aluminiumsulphate forms double salts - called alum, having the general formula M 2 SO 4. It forms many useful alloys with Cu. Mn, Mg, Si and Zn. Hence, aluminium and its alloys find use in packaging, utensil making, construction, aerospace and other transportation industries.
It is used as a conductor for transmission of electricity. Aluminium is alsoused in the alumino-thermite process for production of chromium and manganese from their ores.
General electronic configuration of carbon family is ns2np 2. Ionization Enthalpy:-The first ionization enthalpies of group 14 elements are higher than those of the corresponding group 13 elements. Tin forms compounds in both oxidation states. In diamond each carbon atom undergas SP3hybridisation. Each carbon is tetrahedrally linked to four other carbon atoms.
In graphite, carbon is SP2-hyberdized graphite has a two-dimensional sheet like structure consisting of a number of hexagonal rings fused together. Graphite conducts electricity along the sheet. It is very soft and Slippery FullerenceFullerence was discovered collectively by three scientists namely R.
E Smalley,R. F Curl and H. Since the C-C bond length is very small, it has very high density 3. Diamond Graphite Crystalline, transparent with extra brilliance. Crystalline, opaque and shiny substance Hardest form Soft having soapy touch Bad conductor of electricity Good conductor of electricity High Density 3.
The soot collected on these blankets is lamp black or carbon black or soot. Charcoal is of various forms such as wood charcoal, sugar charcoal, coconut charcoal, animal charcoal etc. These forms contain varying amount of carbon content.
A very pure form of carbon is obtained from sugar. Activated charcoal, a pulverized form whose surface is cleaned. It is used in filters to remove offensive odors from air and colored, foul smelling, bad tasting and toxic chemical as impurities from water.
Coke is an impure form of carbon and is produced when coal is heated strongly in the absence of air as residue in the destructive distillation of coal It is widely used as a reducing agent in metallurgical operations. Graphite occurs in Nature and can also obtained from coke, In graphite, out of four valence electrons, only three form covalent bonds sp2 hybridization with three other carbon atoms.
This forms hexagonal rings as sheets of on atom thickness. These sheets are held together by weak attractive forces one electron of each carbon atom is free and this enables these thin sheets slide over one another.
For this reason graphite is a soft material with lubricating properties. It is insoluble in ordinary solvents. Graphite is a good conductor of heat and electricity because of the present of one free electron on each carbon atom. Graphite is used as a dry lubricant in making electrodes in electric furnaces. It is chiefly used in lead pencils. The number of hydrides and the ease of preparation decrease on going from carbon to lead. The hydrides of germanium are called germanes while those of tin are called the stannanes.
Only lead forms an unstable hydride of the formula, PbH 4 called the plumbane. Si forms SiO 2. Pb forms a number of oxides. Heat The red form of PbO is called litharge and the yellow form is massicot. Pb2O 3 is called lead sesquioxide. GeO 2 , SnO 2 etc. All the elements of group 14 except silicon from monoxides e. Out of these monoxides only CO is neutral, while all other monoxides are basic. Anomalous behaviour of Carbon Carbon is found to differ in many properties from the rest of the members of group This is because of the following:.
Sodium silicate. Silicon and its compounds Silicon, being a second member of group — 14, has a much larger size and lower electronegativity than hat of carbon. As a result silicon does not form double bond with itself or with oxygen. Silicon has vacant 3d-orbitals in its valence shell due to which it can extend its covalency from four to five and six. It does not occur in free state. It occurs mainly in the form of Silica and silicates.
Silicates are formed in rocks and clay as silicates of Mg, Al, K or Fe. Very high purity silicon required for making semiconductors is obtained by reduction of highly purified SiCl 4 form SiHCl 3 with hydrogen followed by purification by zone refining eg. With halogens, Si reacts at elevated temperature forming SiX 4 except fluorine which reacts at room temperature. It is used in the pure form as a starting material for production of silicon polymers Silicones.
It occurs in nature in various forms such as sand, quartz and flint. It is also a constituent of various rocks. It is solid at room temperature. It is insoluble in water. Silica has a three dimensional network structure in which each Si is bonded to four oxygen atoms which are tetrahedrally disposed around silicon atom. Each O atom is shared by two Si atoms. It may be noted that CO 2 is a gas, while SiO 2 is hard solid with very high melting point.
It is used in large amount to form mortar which is a building material. It is also used in the manufacture of glass and lenses. Some of the important silicates are quartz, mica, asbestos, felspar and zeolites. Silica gel When a mineral acid Such as HCl is added to a concentrated solution of a silicate, gelatinous white ppt. When the water content is very low, the solid product is called silica gel. It possesses excellent absorptive properties due to its porous nature and is used for absorbing moisture and an adsorbent in chromatography.
Glass Glass is an amorphous and transparent solid which is obtained by solidification of various silicates and borates of potassium and calcium. It is poured into moulds to get different types of articles, which are allowed to cool gradually.
Nitrogen is the first member of group 15 or VA of the periodic table. The elements of this group are collectively called pnicogens and their compounds as pniconides. Electronic configuration Elements Electronic configuration ns 2 np 3 7 N 1s 2 , 2 s 2 2 p 3 or [He] 2 s 2 2 p 3.
Note: Nitrogen is the most abundant gas in the atmosphere. Phosphorus is the most reactive element in this group and its yellow form is always kept under water. This value shows a decreasing trend in moving down the group from nitrogen to bismuth. Phosphorus, arsenic and antimony exist in the form of discrete tetra atomic molecules such as P4 , As 4 , Sb 4 in which the atoms are linked to each other by single bonds.
Note: M. Boiling point first increases from N to Sb. Boiling point of Bi is less than Sb. Yellow phosphorus can be separated from red phosphorus by reaction with NaOH aq or KOH aq when the former reacts and the latter remains unreacted. Antimony also exists in three forms, viz. In moving down this group,. The tendency of the elements to show —3 oxidation state decreases on moving down the group from N to Bi. This tendency goes on decreasing in moving down the group due to gradual decrease in their bond M—M energies.
Note: Out of the various allotropic forms of phosphorus, black phosphorus is a good conductor of electricity similarity with graphite. All hydrides are pyramidal in shape. The bond angle decreases on moving down the group due to decrease in bond pair—bond pair repulsion. NH 3 is thermally most stable and BiH 3 is least stable. Hence, the decomposition temperature of NH 3 will be the highest. This is due to impurities of diphosphine P2 H 4. Calcium phosphide reacts with water to form phosphine which burns to give clouds of P2 O 5 which acts as smoke screens.
The trihalides are sp 3 -hybridized with distorted tetrahedral geometry and pyramidal shape while pentahalides are sp 3 d- hybridized and are trigonal bipyramidal in shape. The trihalides are hydrolyzed by water and ease of hydrolysis decreases when we move down the group. NF3 is not hydrolyzed due to lack of vacant d-orbital with nitrogen. Except NF3 , the trihalides of nitrogen are unstable and decompose with explosive violence. NF3 is stable and inert. NCl 3 is highly explosive.
Trifluorides and trichlorides of phosphorus and antimony act as Lewis acid. The acid strength decreases down the group. Nitrogen does not form pentahalides due to non-availability of vacant d-orbitals. The pentachloride of phosphorus is not very stable because axial bonds are longer and hence weaker than equitorial bond.
The unstability of PCl 5 makes it a very good chlorinating agent. All pentahalides act as lewis acids since they can accept a lone pair of electron from halide ion. PI5 Does not exist due to large size of I atoms and lesser electronegativity difference between phosphorus and iodine. Down the group, the tendency to form pentahalides decreases due to inert pair effect. Nitrous oxide N 2 O has a sweet taste and its main use is as anaesthetic.
When inhaled in mild quantities it causes hysterical laughter so it is also called Laughing gas. Nitric oxide NO can be obtained by treating a mixture of sodium nitrite and ferrous sulphate with dil. Also P2 O 5 is acidic in nature. N 2 O 5 is the strongest oxidising agent.
Nitroxylic acid Pernitric acid. It acts as a strong oxidising agent. It is tetrabasic. Also exists as a trimer and is monobasic. Anamalous behaviour of Nitrogen Nitrogen is known to differ from other members of the family because of the following facts, i Its small size ii Its high electronegativity iii Its high ionization energy iv Non-availability of d-orbital in the valence shell.
The main points of difference are, 1 Nitrogen is a gas N 2 while other members are solids. Nitrogen and its compounds N 2 was discovered by Daniel Rutherford. It is the first member of group 15 in the periodic table. N 2 is present in many compounds such as potassium nitrate nitre. Sodium nitrate Chile salt peter and many ammonium compounds.
N 2 is an important constituent of proteins in plants and animals in combined state. NH 4 Cl aq. It is a non-toxic gas. Its vapor density is It has very low solubility in water.
It is chemically unreactive at ordinary temp. It is neither combustible nor it supports combustion. Both these compounds are hydrolyzed on boiling with water to give ammonia. However, it cannot be dried with dehydrating agents such as conc. NH 3 is a colorless gas with a characteristic pungent smell called ammonical smell. Liquid ammonia is widely used as a refrigerant due to its high heat of vaporization.
Hydrazine, NH2 — NH2 Hydrazine is prepared commercially by boiling aqueous ammonia or urea with sodium hypochloride in the presence of glue or gelatin. NH3OH is obtained. This is distilled under reduced pressure, over barium oxide to liberate free hydrazine. Physical properties: Anhydrous hydrazine is a colorless fuming liquid m.
It is also soluble in alcohol. It is strongly hygroscopic. Chemical properties: It behaves as a diacid base, Thus with hydrochlorides it forms hydrazine monochloride H2N. Uses: Hydrazine is used as a rocket fuel.
It is also used as a reagent in organic chemistry. Nitrous oxide NO a By the action of cold dil. Oxyacids of nitrogen Name M. Phosphorus and its compounds It is the second member of group 15 VA of the Periodic table. Phosphates are essential constituents of plants and animals.
It is a crystalline solid with garlic odour. It reacts vigorously with Cl 2 to form a mixture of phosphoryl chloride and meta phosphoryl chloride. It is snowy white solid. It readily dissolves in cold water forming metaphosphoric acid. Cold Metaphosphoric acid Het Phosphoric acid.
P4 O10 is a very strong dehydrating agent. H 2 O Triple super phosphate , Phosphatic slag etc. NPK contains nitrogen, phosphorus and potassium. NPK is formed by mixing ammonium phosphate, super phosphate and some potassium salts.
Oxygen is the first member of group 16 or VIA of the periodic table. These except polonium are the ore forming elements and thus called chalcogens. S, Se, and Te because of low electronegativities show more covalent character. Oxygen and its compounds Oxygen is the most abundant element in the earth crust It was discovered by Karl Scheele and Joseph Priestley. It occurs in three isotopic forms: 16 17 18 8O 8O 8O Abundance: Silver oxide Manganesedioxide Barium peroxide Barium oxide.
Note: In the absence of MnO 2 catalyst, the decomposition takes place at K. During this process, N 2 with less boiling point 78 K distills as vapour while O 2 with higher boiling point 90 K remains in the liquid state and can be separated. It is slightly soluble in water and its solubility is about 30 cm 3 per litre of water at K. Physical properties of atomic and molecular oxygen.
Atomic properties Molecular properties Atomic radius pm — 73 Bond length pm — It is quite stable in nature and its bond dissociation energy is very high. Therefore, dioxygen reacts at higher temperatures. However, once the reaction starts, it proceeds of its own. This is because the chemical reactions of dioxygen are exothermic and the heat produced during the reaction is sufficient to sustain the reactions.
Oxides: A binary compound of oxygen with another element is called oxide. On the basis of acid-base characteristics, the oxides may be classified into the following four types,.
Trends of oxides in the periodic Table : On moving from left to the right in periodic table, the nature of the oxides change from basic to amphoteric and then to acidic. However, on moving down a group, acidic character of the oxides decreases. For example in the third group, the acidic character of oxides decreases as:. On the basis of oxygen content the oxides may be classified into the following types, Normal oxides: These contain oxygen atoms according to the normal oxidation number i.
Therefore, these contain oxygen atoms in oxidation state different than —2. For example, KO 2 , PbO2 , etc. Suboxides: These oxides contain less oxygen than expected from the normal valency.
For example, N 2 O. Mixed oxides: These oxides are made up of two simple oxides. Ozone or trioxygen Ozone is an allotrope of oxygen. It is present in the upper atmosphere, where it is formed by the action of U. O 3 Protects us from the harmful U.
Preparation: Ozone is prepared by passing silent electric discharge through pure, cold and dry oxygen in a specially designed apparatus called ozonize. The formation of ozone from oxygen is an endothermic reaction. For the better yield of ozone: a Only pure and dry oxygen should be used. Physical properties: Ozone is a light blue colored gas, having pungent odour. It is heavier than air.
Its vapour density is Therefore, ozone oxidises a number of non-metals and other reducing agents. During this reaction mercury loses its meniscus and starts sticking to the sides of the glass. This is known as tailing of mercury. Mercurous oxide formed in this reaction dissolves in mercury and starts sticking to the glass surface. It acts as a bleaching agent for vegetable coloring matter.
Sulphur and its compounds Sulphur is the second member of oxygen family and belongs to group VI A of the periodic table. It occurs in the Free State as well as in combined state. Sulphure occurs mainly as sulphides and sulphates. All other varieties of sulphur gradually change into this form on standing.
On removing the crust, needle shaped.. It is dull yellow in colour, :S.. S S: soluble in CS 2 and stable only above K. Below this temperature it.. O C.. S changes into rhombic form. Thus, at K both these varities co-exist. This temperature is called.. S transition temperature and the two sulphurs are called enantiotropic substances. It also exist as molecules similar to that of rhombic sulphur but the symmetry of the crystals is different.
It consists of long zig-zag chains of S-atoms. It is colorless gas having foul smell resembling that of rotten eggs. Sulphur is sp hybridized. Some of these are. OH OH. Its salts known as O. It is often called king of chemicals, since it is one of the most useful chemicals in industry.
V2O5 is, however, preferred since is much cheaper than Pt and is also not poisoned by arsenic impurities. If impurities are present, Impure SO2 passed through purifying unit.
Purifying unit Pure. SO2 Conc. Properties: H2SO4 has high b. It has strong affinity for H2O and a large amount of heat is evolved when it is mixed with water. It neutralizes alkalies, liberates CO2 from carbonates and bicarbonates. Uses : H2SO4 is used i in the preparation of fertilizers like NH4 2 SO 4 and super phosphate of lime, ii in lead storage batteries iii in preparation of dyes, paints and explosives iv in textile and paper industry v for training of tanning vi as a dehydrating agent.
Physical properties: 1 Sodium thiosulphate is a colourless crystalline solid. In the hydrated form, it is called hypo. The solution turns milky yellow due to sulphur. Sodium dithiosulphate argentate I compex. Uses of sodium thiosulphate 1 It is largely used in photography as a fixing agent.
Fluorine is the first member of group 17 or VIIA of the periodic table. These are known as halogen because their salts are found in sea water. Halogen is a Greek word meaning a sea salt. F2 — gas, Cl 2 — gas, Br2 — corrosive liquid, I 2 — volatile solid. I 2 is a least soluble in water. This tendency decreases on moving down the group. Fluorine gives fumes in moist air.
This is due to the formation of HF, which is a liquid and can absorb moisture to form liquid droplets and therefore, gives fumes with moist air. Iodine is only slightly soluble in water.
HCl is also called Muriatic acid. However, a number of compounds of halogens with oxygen have been prepared by indirect methods. Only two compounds of fluorine with oxygen, i. Chlorine forms largest number of oxides i. In all these compounds, bonds are largely covalent. All the oxides of halogens are powerful oxidizing agents. These compounds are very reactive and are unstable towards heat.
The stability of oxides is greatest for iodine while bromine oxides are the least stable. For a particular halogen, higher oxides are more stable than the lower ones. Iodine-oxygen bond is stable due to greater polarity of the bond due to larger electro negativity difference between I and O while in chlorine-oxygen bond, the stability is gained through multiple bond formation involving the d-orbital of chlorine atom.
Bromine lacks both these characteristics and hence forms least stable oxides. Oxides of chlorine, bromine and iodine are acidic and the acidic character increases as the percentage of oxygen increases in them. Iodine also forms l2O4 and l4O9 compounds which are believed not to be true oxides but are basic iodyliodate, IO IO3 and normal iodine triodate, I IO3 3 having tripositive iodine as the cation. It is paramagnetic due to odd number of electrons having three-electron bond.
It is regarded as a mixed anhydride of chloric and chlorous acids. The acidic character of the oxoacids increases with increase in oxidation number, i. As the number of oxygen atoms in an ion increases there will be a greater dispersal of negative charge and thus greater will be the stability of ion formed.
For different halogen having the name oxidation number, the thermal stability decreases with increase in atomic number i. The main reason for their formation is the large electronegativity and the size differences between the different halogens. Taking A as the less electronegative and B as the more electronegative halogen, they are divided into the following four types the less electronegative halogen A is always written first.
Thus ClF is thermally more stable as compared to IBr. IF3, ClF3, BrF3 have distorted trigonal bipyramidal dsp3-hybridization structures of T- shape due to two lone pairs in equatorial positions ICl3 is dimeric, I2Cl6 and has a planar structure. BrF5, IF5 have distorted octahedral d2sp3-hybridization shapes or square pyramidal due to a lone pair one of the axial positions.
These cause ozone depletion. In this process, NaOH and H2 are by products. Tincture of iodine is an antiseptic. Iodized salt is used to prevent the occurrence of common goiter. Helium is the first member of group 18 or zero of the periodic table.
These are collectively called as inactive gases or inert gases. However, these are now called noble gases as some compounds of these gases have been obtained under certain specific conditions.
Therefore, ionisation energy of noble gases is very high. On the other hand their electron affinity is zero. However the value of heat of vaporization increases with atomic number down the group and this shows that there is an increasing polarisability of the larger electronic clouds of the elements with higher atomic number.
Their solubility generally increases with the increase in atomic number down the group. The extent of adsorption increases down the group. Ease of liquefication increases down the group from He to Rn. Helium has the lowest boiling point 4. The ease of liquefication increases down the group due to increase in intermolecular forces. The elements helium He , neon Ne , argon Ar , krypton Kr , xenon Xe and radon Rn , constitute zero group of the periodic table.
These are gases at ordinary temperature and do not have chemical reactivity and therefore, these are called inert gases. Except radon, all these gases are present in atmosphere in the atomic state.
The natural gas contains hydrocarbons methane etc. The natural gas is compressed to about atm and cooled to 73K. He remains unliquefied while other gases get liquefied. Fractional distillation of air gives O2, N2 and mixture of noble gases. The individual gases may be obtained by adsorption of air on coconut charcoal. The charcoal adsorbs different gases at different temperatures and can be collected.
In , N. Orange yellow. Fluorides: Xenon forms three compounds with fluorine. Structure: XeF2 has trigonal bipyramid geometry due to sp 3 d-hybridization of Xe. Three equatorial positions are occupied by lone pairs of electrons giving a linear shape to the molecule. It also forms addition compounds with reactive pentafluorides like SbF5, TaF5 etc. Structure: XeF4 has square planar shape due to sp 3 d 2 hybridization of Xe giving octahedral geometry with two trans positions occupied by lone pairs of electrons.
It also acts as a strong fluorinating agent. Structure: XeF6 has pentagonal bipyramid geometry due to sp3d3 hybridization.
One trans position is occupied by a lone pair giving a distorted octahedral shape. MF where M represents the alkali metal. Structure: XeO3 has tetrahedral geometry due to sp 3 hybridization of Xe. One of the hybrid orbitals contains a lone pair of electrons giving a trigonal pyramidal shape. Properties: It is a colorless solid, highly explosive and powerful oxidizing agent.
Structure: XeO4 has tetrahedral structure due to sp 3 hybridization of Xe. Structure: XeOF2 has trigonal bipyramid geometry due to sp 3 d-hybridization of Xe. Two equatorial positions are occupied by lone pairs of electrons giving a T-shape to the molecule. Structure: XeOF4 has octahedral geometry due to sp 3 d 2 hybridization of Xe.
One trans position is occupied by a lone pair giving pyramid shape to the molecule. Properties: It is a colorless volatile liquid which melts at K. Structure: XeO2F2 has trigonal bipyramid geometry due to sp 3 d-hybridization of Xe. One equatorial position is occupied by a lone pair of electrons giving a see-saw structure shape to the molecule.
Properties: It is a colorless solid which melts at K. It is also used in filling Geiger-Counter tubes and thermionic tubes. A mixture of krypton and xenon is also used in some flash tubes for high speed photography.
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Physical properties 1 Physical state i All are silvery white, soft and light solids. Li differs from other alkali metals in the following respects: 1 It is comparatively harder than other alkali metals. Li and R. MgX are soluble in organic solvent. It is radioactive in nature. Physical properties 1 Physical state: All are greyish-white, light, malleable and ductile metals with metallic lustre.
Be Mg Ca Sr Ba Ra First ionisation energy k J mol-1 Second ionization energy kJ mol-1 iii The higher values of second ionization energy is due to the fact that removal of one electron from the valence shell, the remaining electrons are more tightly held in which nucleus of cation and thus more energy is required to pull one more electron from monovalent cation.
CaCl2 SrCl2 BaCl2 Brick red colour Crimson colour Grassy green colour Structure of BeCl2 In the solid phase polymeric chain structure with three centre 2 electron bonding with Be-Cl-Be bridged structure is shown below, PM Be 98 82 Be pm Be o o In the vapor phase it tends to form a chloro-bridged dimer which dissociates into the linear triatomic monomer at high temperature at nearly K.
BeF3 -, AlH4 -. HCl to liberate H2. Difference between alkali metals and alkaline earth metals Properties Alkaline earth metals Alkali metals Electronic Two electrons are present in the One electron is present in the configuration valency shell.
Hydrated salt on heating in air undergoes partial hydrolysis. Mg3 B2. Other members form simply alloys. Some important similarities between boron and silicon are given below, 1 Both boron and silicon are typical non-metals, having high m.
Note: Aluminum is refined by Hoope's electrolytic process. K — ii The m. Ionization energy kJ mol-1 C Si Ge Sn Pb IE1 IE2 IE3 IE4 ii The first ionization energies of group 14 elements are higher than their corresponding group 13 elements because of smaller size.
Difference between diamond and graphite Diamond Graphite Crystalline, transparent with extra brilliance. This is because of the following: i Its smallest size ii Its high electronegativity iii Its property to catenate iv Absence of d-orbitals in it.
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