Group 13 (IIIA) Elements PDF

# Group 13 (IIIA) elements ## The electronic configuration - The electronic configuration of the outermost energy levels of these elements may be represented as $ns^2np^1$. | Element | Symbol | Atomic number | Electronic structure | Oxidation states | |---|---|---|---|---| | Boron | B | 5 | [He]...

# Group 13 (IIIA) elements ## The electronic configuration - The electronic configuration of the outermost energy levels of these elements may be represented as $ns^2np^1$. | Element | Symbol | Atomic number | Electronic structure | Oxidation states | |---|---|---|---|---| | Boron | B | 5 | [He] $2s^2$ $2p^1$ | **III** | | Aluminum | Al | 13 | [Ne] $3s^2$ $3p^1$ | I, **III** | | Gallium | Ga | 31 | [Ar] $3d^{10}$ $4s^2$ $4p^1$ | I, **III** | | Indium | In | 49 | [Kr] $4d^{10}$ $5s^2$ $5p^1$ | I, **III** | | Thallium | Tl | 81 | [Xe] $4f^{14}$ $5d^{10}$ $6s^2$ $6p^1$ | I, **III** | - The most important oxidation states are shown in bold. ## General properties - Generally, they occur scarce in nature except aluminum. - They possess three valence electrons and they are metals except boron. - All these elements in their compounds exhibit the oxidation state of +3 and +1. - At room temperature all the five of these elements are solids, soft, and have low melting points except boron. - The melting point of boron is very high because it exists as a giant covalent polymer both in liquid and solid states. - They are chemically reactive at moderate temperatures except boron. ## Chemical Reactivity ### 1. Hydrides - None of the group 13 elements reacts directly with hydrogen. - A number of hydrides of these elements have been prepared by indirect methods. ### 2. Oxides and Hydroxides - Almost all the elements of group 13 form oxides and hydroxides of the composition $M_2O_3$ and $M(OH)_3$, respectively. | Compound | Property | |---|---| | $B(OH)_3$ and $B_2O_3$ | Acidic | | $Al(OH)_3$ and $Al_2O_3$ | Amphoteric | | $Ga(OH)_3$ and $Ga_2O_3$ | Amphoteric | | $In(OH)_3$ and $In_2O_3$ | Basic | | $TI(OH)_3$ and $TI_2O_3$ | Strong base | - Basic Character Increases → ### 3. Halides - Al, Ga, In, and Tl react with halogens to give binary halides. - All the halides of group 13 elements are known except Tl(III) iodide. - The fluorides are ionic and have high melting points. - The chlorides, bromides, and iodides are essentially covalent compounds with low melting points. - The trihalides of group 13 elements are strong Lewis acids. - As a consequence of its strong Lewis acid character, $BF_3$ is used as a catalyst in several industrial processes. - Anhydrous aluminum chloride is used as a catalyst in several organic reactions (Friedel-Craft's reaction). # Boron (B) - Boron occurs in the earth crust up to 10 ppm. - Generally, it is a rare substance. - It is shiny black metalloid generally occurs in pure form. - It is hard as well as a good conductor. ## Isotops - Boron has 2 naturally occurring isotopes, which are $^5B^{11}$ and $^5B^{10}$ available in 80.1% and 19.9% proportions, respectively. - $^5B^{10}$ is called the enriched boron while $^5B^{11}$ is known as the depleted boron. ## Extraction of boron - 1 - The mineral of boron is treated with a solution of $Na_2CO_3$ to separate boron as borax ($Na_2B_4O_7$). - Boron mineral + $Na_2CO_3$ → $Na_2B_4O_7$ - 2 - The separated borax is treated with conc. $H_2SO_4$ to yield boric acid ($H_3BO_3$) as follows: - $Na_2B_4O_7.10H_2O + H_2SO_4$ → $Na_2SO_4 + 4H_3BO_3 + 5H_2O$ - 3 – Tow molecules of boric acid are heated to give $B_2O_3$ as shown below: - $2H_3BO_3$ → $B_2O_3 + 3H_2O$ - 4 - reduction of $B_2O_3$ with magnesium metal yields pure boron as follows: - $B_2O_3 + 3Mg$ → $2B + 3MgO$ ## Chemical Properties ### Action of air - Boron is unaffected by air at ordinary temperature, but when heated in air to about 975K, it burns forming boron trioxide and a little boron nitride, BN. - $4B + 3O_2$ → $2B_2O_3$ - $2B + N_2$ → $2BN$ ### With acids - Amorphous boron dissolves in hot concentrated sulphuric and in nitric acid to form boric acid. - $B + 3HNO_3$ → $H_3BO_3 + 3NO_2$ - $2B + 3H_2SO_4$ → $2H_3BO_3 + 3SO_2$ ### With caustic alkali - It dissolves in fused caustic alkali and forms boric acid. ### As a reducing agent - Boron is a powerful reducing agent and it reduces a large numbers of metal oxides. - $3CuO + 2B$ → $B_2O_3 + 3Cu$ - $Fe_2O_3 + 2B$ → $B_2O_3 + 2Fe$ ### With metals - It combines with metals (except Cu, Ag, and Au) at high temperature in the electric furnace to form borides. ### With non-metals - Boron combines with nitrogen, chlorine, bromine, and carbon at higher temperature forming boron nitride, BN, boron trichloride, $BCl_3$, boron tribromide, $BBr_3$, and boron carbide, $B_4C_3$, respectively. - Boron carbide is probably the hardest substance known. # Ox compounds ## Boron Oxide $B_2O_3$ (Boric acid anhydride) ### Preparation of $B_2O_3$: - $4B + 3O_2$ Δ $2B_2O_3$ - $2H_3BO_3$ Δ $B_2O_3 + 3H_2O$ - $B_2O_3$ combines with water forming: - 1 - ortho boric acid: $H_3BO_3$ - 2 - meta Boric acid: $HBO_2$ - 3 - tetra basic boric acid: $H_2B_4O_7$, which reacts with NaOH or $Na_2CO_3$ forming borax $Na_2B_4O_7$ # Aluminum (Al) - It is the third largest available metal in the earth’s crust. - It is the only metal that is available abundantly in this family. - Aluminum occurs in the earth crust up to 81,300 ppm. - It is bluish white in its purest form, silvery in appearance while in general use. - The fresh metal on exposure to moist air loses its shining due to formation of oxide layer on its surface. - It is a good conductor of electricity and heat and forms cations and ionic bonds with non-metals and non-poisonous, and non-magnetic in nature. - It is soft as well as light weight. - Silicon and iron is added with them to increase hardness. ## Isotopes - Aluminum has nine isotopes whose mass number ranges from 23 to 30. - Only $Al^{26}$ (stable isotope) and $Al^{27}$ (radio active isotope, $t_{1/2} = 7.2 years$). ## Extraction of Aluminum - Pure Aluminum metal is extracted from bauxite in a three-stage process. - a) Purification of Bauxite (Bayer’s Process) to obtain pure Alumina. - b) Electrolysis of pure Alumina in molten cryolite ($Na_3AIF_6$) (Hall’s process). - c) Refining of Aluminium (Hoopes process). ## Purification of bauxite - Bauxite contains silicon dioxide ($SiO_2$ ), iron oxides, and titanium(IV) oxide as impurities. - The bauxite ore is digested with a concentrated solution of sodium hydroxide at 473-523 K and 35-36 bar pressure. - Aluminum oxide and silica dissolve to form sodium aluminates and sodium silicate respectively leaving behind iron oxide and $TiO_2$, which are filtered off. - $Al_2O_3(s) + 2NaOH (aq) + 3H_2O (l)$ → $2 Na [Al(OH)_4] (aq)$ - The filtrate containing sodium aluminates and sodium silicate is diluted and seeded with freshly precipitated aluminum hydroxide, which induces the precipitation of aluminum hydroxide leaving behind sodium silicate in solution. - $Na [Al(OH)_4] (aq)$ $H_2O$→ $Al(OH)_3 (s) + NaOH (aq)$ - The aluminum hydroxide is filtered dried and calcined at 1473 °K to yield pure alumina. ## Chemical Properties ### Action of air - (a) Aluminum is not affected by dry air but in moist air a thin film of oxide is formed on its surface. - (b) It burns with oxygen with a brilliant white light with the evolution of heat. - $4Al + 3O_2 $ → $2A1_2O_3$ ### Action of water - Aluminum is not affected by water due to the formation of the protected thin film of oxide on its surface. ### Action of acids - Aluminum dissolves in dilute hydrochloric acid forming aluminum chloride with the evolution of di-hydrogen gas. - $2Al + 6HC1$ → $2AlCl_3 + 3H_2↑$ - Aluminum is not affected by concentrated or diluted nitric acid because nitric acid is oxidizing acid and forming a thin film of $Al_2O_3$ on the surface. - This thin film prevents contacting the acid with the metal. - Aluminum is not attacked easily by dilute sulphuric acid. - This probably is due to the insolubility of oxide layer (present on its surface) in the acid. - However, it dissolves in hot and concentrated sulfuric acid to form sulpher dioxide. - $2Al + 6H_2SO_4$ → $Al_2(SO_4)_3 + 2SO_2 + 6H_2O$ ### With alkalis - It dissolves in the concentrated alkali solutions forming metal aluminates ($MA1O_2$). - $Al + NaOH + H_2O$ → $NaAlO_2 + 3/2 H_2O$ # Group 14 (IVA) Elements ## The electronic configuration - The electronic configuration in the valence shells of the carbon family elements is $ns^2 np^2$. | Name of element | Symbol | Atomic number | Type | Oxidation state | Electronic configuration | |---|---|---|---|---|---| | Carbon | C | 6 | Non metal | **IV** | [He] $2s^22p^2$ | | Silicon | Si | 14 | Metalloid | (II), **IV** | [Ne] $3s^23p^2$ | | Germanium | Ge | 32 | Metalloid | II, **IV** | [Ar] $3d^{10}$ $4s^24p^2$ | | Tin | Sn | 50 | Metal | II, **IV** | [Kr] $4d^{10}$ $5s^25p^2$ | | Lead | Pb | 82 | Metal | II, **IV** | [Xe] $4f^{14}$ $5d^{10}$ $6s^26p^2 | - The most important oxidation states are shown in bold. ## General Properties - The elements of group 14 occur as elemental forms and in the form of compounds in nature. - They are relatively non-reactive and usually tend to form covalent compounds with exceptions of tin and lead that form ionic compounds. - The oxidation states of these elements are usually +4 and +2 for heavier elements because of the inert pair effect. # Carbon (C) - Carbon is the first element known to humans and is the fourth most abundantly found element. - Carbon exists both in elemental form and as allotropes, the most common being diamond and graphite. - Carbon exists as metal carbonates, metal carbides, and oxides of carbon. - Carbon is present as carbon dioxide in the atmosphere. - It also exists in the form of organic compounds in wood, coal, petroleum, and natural gas. ## Allotropes of Carbon - **Definition:** The existence of one element in different forms, having different physical properties, but similar chemical properties is known as allotropy. ### 1 - Amorphous form - Coal, Coke, Charcoal (or wood charcoal), Animal Charcoal (or bone black), Lamp black, Carbon black, Gas carbon, and Petroleum coke. ### 2 - Crystalline form: Diamond, Graphite - Diamonds and graphite are two crystalline allotropes of carbon. - Diamond and graphite both are covalent crystals, but, they differ considerably in their properties. -  - **Covalent bond** - **Carbon atom** - **Carbon atoms** - **Weak binding forces** - **Covalent bond** - **Structure of Diamond** - **Structure of Graphile** ## Comparison of the Properties of Diamond and Graphite | Property | Diamond | Graphite | |---|---|---| | Occurence | It occurs naturally in free state. | It occurs naturally and is manufactured artificially. | | Hardness | It is the hardest natural substance known. | It is soft and greasy to touch. | | Density | It has high relative density (about 3.5). | It has a lubricant character and a low density. | | Transparency | It is transparent and has high refractive index. | It is black in color and opaque. | | Conductivity | It is non-conductor of heat and electricity. | It is a good conductor of heat and electricity. | | Burning behavior | It burns in air at 900 °C to give $CO_2$. | It burns in air at 700-800 °C to give $CO_2$. | | Crystal structure | It occurs as octahedral crystals. | It occurs as hexagonal crystals. | | Solubility | It is insoluble in all solvents. | It is insoluble in all ordinary solvents. | ## Resons - Those differences in the properties of diamond and graphite are due to the difference in their structures. - In diamond, each C atom is linked to its neighbors by four single covalent bonds. - This leads to a three-dimensional network of covalent bonds. - In graphite, the carbon atoms are arranged in flat parallel layers as regular hexagons. - Each carbon in these layers is bonded to three others by covalent bonds. - Graphite thus acquires some double bond character. - Each layer is bonded to adjacent layers by weak van der Waals forces. - This allows each layer to slide over the other easily. - Due to this type of structure, graphite is soft and slippery and can act as a lubricant. - Graphite is also a good conductor of electricity due to mobile electrons in it. ## Chemical Properties of Carbon ### Burning - All allotropic forms of C burn in air or oxygen to form $CO_2$ (when air supply is sufficient) and CO (when air supply is insufficient). ### Reducing properties - C is a strong reducing agent and reduces many metallic oxides to metals. ### Formation of carbides - When heated with certain oxides, it forms the corresponding carbides e.g. - $CaO + 3C$ → $CaC_2 + CO$ ### 4. Catenation Property - **Definition:** Catenation is the binding of an element to itself through covalent bonds to form chain or ring molecules. - This is the most important and unique characteristics of carbon. - It has the unique capability of bonding with other C atoms to form long chains. - C can form single, double, or triple bonds with other C atoms. - This property leads to the formation of hydrocarbons ... etc., and is the basis of a very important branch of science “organic chemistry”. ## Compounds of Carbons with Oxygen ### 1 - Carbon monoxide (CO) - Carbon monoxide is formed, when incomplete combustion of carbon or carbon containing fuels takes place. - $C + 1/2O_2$ → $CO(g)$ - CO is present in automobile exhausts (when there is incomplete combustion), and volcanic gases, etc. ### Preparation - Carbon monoxide can be prepared by any of the following methods: - By the reduction of carbon dioxide with carbon: - $CO_2 + C$ heat $2CO$ - By heating oxalic acid with sulphuric acid, where sulphuric acid acts as a dehydrating agent. - $COOH$ $COOH$ $H_2SO_4$ → $CO + CO_2$ - $H_2O$ ### Properties - Carbon monoxide (CO) is a colorless, odorless, and a poisonous gas. - Carbon monoxide reacts with the hemoglobin in the red blood cells to form carboxy-hemoglobin. - Carboxy-haemoglobin is not able to carry oxygen. - This results in a deficiency of oxygen in the body, when CO is inhaled, causing suffocation and even death. ### Combustibility - Carbon monoxide burns in air with a pale-blue flame giving carbon dioxide. - $2CO + O_2$ → $2CO_2(g) + Heat$ ### Reducing character - Carbon monoxide is a reducing agent. - It reduces many oxides to the respective metal. - $Fe_2O_3 + 3CO$ heat → $2Fe + 3CO_2$ - $ZnO + CO$ → $Zn + CO_2$ ### With hydrogen - When heated with hydrogen, to 420 - 670 K under 300 atm pressure and in the presence of a catalyst ($ZnO + Cu$ ), carbon monoxide reacts to form methyl alcohol. - $CO + 2H_2$ $ZnO + Cu$ $CH_3OH$ 420-670 K, 300 atm methyl alcohol ### With chlorine - Carbon monoxide reacts with chlorine to give phosgene. - $CO + Cl_2$ sunlight $COCl_2$ phosgene (or carbonyl chloride) ### With sodium hydroxide - Carbon monoxide reacts with sodium hydroxide under pressure to form sodium formate. - $CO + NaOH$ pressure $HCOONa$ sodium formate ### Formation of metal carbonyls - Many transition metals combine with carbon monoxide under suitable conditions to form carbonyls. - $Ni + 4CO$ 320-340 K $Ni(CO)_4$ - OC CO / \ / \ Ni \ / \ / OC CO - nickel - carbonyl - On heating to higher temperatures, those carbonyls decompose to give pure metal. - $Ni + 4CO$ 320-340 K → $Ni(CO)_4$ 450 K → $Ni + CO(g)$ - Impure nickel pure - carbonyl ## Uses - CO is used as a fuel in the form of producer gas or water gas. - (a) Producer gas is obtained by passing air over red hot coke at 1300 Κ. - $2C + O_2 + 4N_2$ → $2CO + 4N_2$ - Red from - hot air produær gas - (b) Water gas is obtained by passing steam over hot coke: - $C$ + $H_2O$ → $CO + H_2$ - red steam water - hot gas - For manufacturing methanol and synthetic petrol. - For manufacture of phosgene used in dye industry and warfare. - In metallurgy as a reducing agent.