The Nitrogen Family
Elements in 15th group are known as ‘The Nitrogen Family’. The family includes the following elements:
|
Elements |
Symbol | State |
Metallic Properties |
|
Nitrogen |
N | Gas | Non-metal |
| Phosphorus | P | Solid |
Non-metal |
|
Arsenic |
As | Solid | Metalloid |
| Antimony | Sb | Solid |
Metalloid |
|
Bismuth |
Bi | Solid | Metal |
Occcurence : Nitrogen – Nitrogen is found in the molecular form in the atmosphere. It comprises 75% by mass and 78% by volume of the atmosphere. It is also found in Earth’s crust in the form of Chile Saltpetre(Sodium Nitrate : NaNO3) and Indian Saltpetre(Potassium Nitrate-KNO3). In the form of protein, Nitrogen is also available in plants and animals.
Phosphorus : Minerals of the apatite family are main source of phosphorus as flourapatite : Ca9(PO4)6.CaX2 where X =F, Cl and Br. In the animal and plant matter nitrogen is an essential component. It is also found in bones of animals. As phosphoproteins it is available in milk and eggs.
Arsenic, Antimony & Bismuth : They are found in sulphide minerals.
Properties of 15th group elements :
◆ Atomic properties :
● Electronic configuration : The electronic configuration of the outermost shell is ns2np3. Due to half filled p orbital these elements are quite stable.
● Atomic & ionic radio :
Reactivity towards oxygen : Group 15 elements form oxides by reacting with oxygen of the form E2O3, E2O4 and E2O5 .Ex: N2O3, N2O4, P2O5, As2O5 etc.
Key Points : 1. Among oxides the acidic nature increases with increase in the oxidation state.
2. The acidic nature also increases with increase in the percentage of oxygen.
3. In the group, the acidic nature decrease with increase in atomic number due to increase in the metallic character.
|
E2O3 Type Oxides of |
Nature |
|
Nitrogen & Phosphorus |
Purely acidic |
|
Arsenic & Antimony |
Amphoteric |
|
Bismuth |
Basic |
4. The stability of oxides decreases down the group.
Reactivity towards Hydrogen : Group 15 elements react with Hydrogen to form hydrides of the form EH3. Ex : NH3 (Ammonia), PH3 (Phosphine), BiH3 (Bismuthine) etc.
Key Points : 1. The thermal stability decreases down the group because the tendency to form covalent bond decreases as the size of atoms increases which leads to increase in the metallic character.
Amines
When one or more hydrogen atoms of ammonia molecule are replaced by alkyl or aryl group amines are formed. These are also called derivatives of ammonia.
Classification of amines: Amines can be classified into three categories:
I.Primary amines: If one hydrogen atom is replaced by R or Ar, we get a primary amine.
II.Secondary amines: If two hydrogen atoms are replaced by alkyl or aryl group we get a secondary amine.
III.Tertiary amines: If three hydrogen atoms are replaced by alkyl or aryl group, we get a tertiary amine.
Alcohols, Phenols & Ethers
Intro: When a hydrogen atom from a hydrocarbon whether aliphatic or aromatic is replaced by -OH group alcohols and phenols are formed.
Ex:
But, when a hydrogen atom from a hydrocarbon whether aliphatic or aromatic is replaced by alkoxy or aryloxy group(R-O/Ar-O) alcohols and phenols are formed.
Ex:
Classification
Haloalkanes & Haloarenes
Intro: When hydrogen atoms are replaced by halogens in hydrocarbons whether aliphatic or aromatic, alkyl halide (haloalkanes) and aryl halide(haloarenes) are formed.
Difference between haloalkanes and haloarenes:
1.In haloalkanes, halogens are attached to sp3 hybridised carbon atoms of alkyl group.
However, in haloarenes halogens are attached to sp2 hybridised carbon atoms of aryl group.
Coordination Compounds
Compounds in which transition metals make several anions or neutral molecules are called coordination compounds. Ex: Chlorofyll, haemoglobin, vitamin B-12 etc.
Werner’s theory for coordination compounds: In 1898, a swiss chemist propounded his theory of coordination compounds. The main points of this theory are as follows:
1. Metals show two types of linkages or valences- primary and secondary in coordination compounds.
2. The primary valences are normally ionisable and are satisfied by anions(negative ions).
3. The secondary valences are nonionisable.
4. The ions/groups bound by the secondary linkages to the metal have characteristic spatial arrangements corresponding to different coordination numbers.
Isomerism in coordination compounds: Compounds having same molecular formula but different structures are called and this phenomenon is called isomerism.
Coordination compounds show two types isomerism: 1. Structural isomerism and 2. Stereo isomerism
I.Structural isomerism : Isomerism due the difference in the structures of compounds is called structural isomerism. This isomerism is of four types:
2. Stereo or space isomerism : The isomerism due to the different relative positions of the ligands is known as stereo isomerism. This isomerism is of two types :
I. Geometrical isomerism : The isomerism in which isomers differ in the spatial distribution of atoms or groups about the central atom is known as geometrical isomerism. It is also known as cis-trans isomerism.
Ex :
Hydrocarbon
Definition: The compounds which are made up of carbon and hydrogen are called hydrocarbons.
Types of hydrocarbons: Hydrocarbons are of mainly three types:
I. Saturated, II. Unsaturated and III. Aromatic
I. Saturated hydrocarbons: Such hydrocarbons which are formed by C-C single bond or C-H single bond are called saturated hydrocarbons.
II. Unsaturated hydrocarbons: Such hydrocarbons which are formed by C-C double or triple or both bonds are called unsaturated hydrocarbons.
Metallurgy
Metals are very important for us. Many useful things like utensils, different types of tools, vehicles, tanks etc are made up of metals. But, metals are not easily available. Only a few metals are found in free state. Maximum metals are found in the combined form i.e. mineral in earth’s crust.
Ore : A mineral from which the extraction of a metal is feasible and economical is called an ore.
Abundance of metals : Aluminium is the most abundant element among metals. It is 8.3% by weight in earth’s crust. The main ores of some important metals are as follows:
|
Metal |
Ores |
Composition |
|
Aluminium |
Bauxite
Kaolinite |
AlOx(OH)3-2x Where 0<x<1 </x<1
Al(OH)4.Si2O5
|
|
Iron |
Haematite
Magnetite Siderite Iron pyrite |
Fe2O3
Fe3O4 FeCO3 FeS2 |
|
Copper |
Copper pyrite
Malachite Cuprite Copper Glance |
CuFeS2
CuCO3 . Cu(OH)2 Cu2O Cu2S |
|
Zinc |
Zinc Blende or Sphalerite
Calamine Zincite |
ZnS
ZnCO3 ZnO |
Metallurgy : The whole technological and scientific process of the isolation of a metal from its ore is called metallurgy.
Gangue : An ore contains several unwanted impurities with a metal which are called gangue.
Concentration of ores : The process of removing guange from an ore is called the concentration of ore.
There are different methods of the concentration of the ores of different metals. Some of them are as follows :
1. Hydraulic washing : This method is based on the difference in specific gravities of the ore and the gangue particles.
Procedure : In this method, water with high speed is drawn on ore particles due to which lighter gangue particles flow with water and ore particles are left behind.
2. Magnetic separation method : This method is based on the differences in magnetic properties of the ore components.
Procedure : In this method, the powdered ore is placed over a conveyer belt which passes over a magnetic roller. The ore particles fall near the roller due to the attraction and gangue particles fall far from the roller.
◆ Refining : Metals obtained from the extraction process are not pure. They still have some impurities. The process of removing these impurities is called refining. For different metals, different refining processes are used.
I. Distillation(Zn/Hg) : The metals with low boiling points are refined by distillation. In this method, the metal with impurities is heated, due to the low boiling point metal vaporizes and it is collected in a flask and impurities are left behind.
II. Liquation(Sn) : This method is suitable for metals having low melting points. In this method, the metal with impurities is heated, due to the low melting point metal vaporizes and it is collected in a flask and impurities are left behind due to their high melting point.
Organic Chemistry Basics
The branch of Chemistry which deals with compounds of carbon and hydrogen i.e. hydrocarbons and their derivatives is called Organic Chemistry.
Lavoisier was the first scientist who stated that carbon and hydrogen are the essential constituents of organic componds.
Vital force theory : A Sweedish chemist Berzelius in 1815 stated that organic compounds can’t be prepared in laboratory because some mysterious forces are responsible for their formation. This theory was called vital force theory.
1st synthesized compound : Wohler prepared the first organic compound urea in laboratory and then the vital force theory was rejected.
Electrochemistry
Electrochemistry is the study of production or consumption of electrical energy in a chemical reaction.
Many chemicals are formed by chemical reactions in which electricity is used. For example: sodium hydroxide, chlorine, fluorine etc.
Electrochemical cells:
I. Galvanic or voltaic cell:
● Gibbs-Helmholtz Equation : The chemists Gibbs and Helmhotz derived a mathematical way to find the value of Gibbs energy as follows:
∆G = ∆H + T(d(∆G)/dT)p
Updated on 9 Aug 2019…
Diwakar Verma
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