Elements in 15th group are known as ‘The Nitrogen Family’. The family includes the following elements:
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
Nitrogen & Phosphorus
Arsenic & Antimony
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.
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.
Intro: When a hydrogen atom from a hydrocarbon whether aliphatic or aromatic is replaced by -OH group alcohols and phenols are formed.
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.
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.
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.
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.
The branch of Chemistry which deals with the compounds of carbon is called Organic Chemistry.
Importance of organic chemistry: Without carbon we can’t imagine life on the earth. The number of compounds of only carbon is equal to the number of compounds of all other elements. Many useful products like clothes, rubber, medicines, fuel etc are only due to carbon.
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.
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…