1) The atomic radius of group 15 elements increases down the group due to increases in the size of an atom.
2) The ionic radius of group 15 elements increases down the group due to an increase in the size of an atom.
3) Ionization enthalpy decreases down the group due to an increase in the size of an atom.
4) Electronegativity decreases down the group due to an increase in the size of an atom.
Physical properties of group 15 element:-
1) Boiling point: - boiling point increases down the group. From N to Bi
2) Melting point: - the melting point of group 15 elements increases from Nitrogen to Arsenic and then decreases up to Bismuth.
3) -3 oxidation states are decreasing down the group due to increases in the size of the atom and metallic character.
4) +3 oxidation states are increases down the group due to inert pair of electrons.
5) +5 oxidation state decreases down the group due to inert pair of electrons.
6) Nitrogen does not have a d orbital to accommodate electrons from other elements to form a bond. Due to its small size and high electronegativity, NH3 exhibits hydrogen bonding in the solid-state as well as in the liquid state. But P is less electronegative than N so it does not exhibit hydrogen bonding in the liquid state. Hence PH3 has a lower boiling point than NH3
7) Due to a decrease in stability of hydrides from NH3 ton BiH3 which can increases the reducing properties from BiH3 to NH3. Hench BiH3 is the strongest reducing agent.
8) Preparation of Dinitrogen: -
a) commercially it is prepared by liquefaction and fractional distillation of air.
b) Industrially it is prepared by treating with ammonium chlorite with nitrite.
9) Use of Dinitrogen:- Dinitrogen is used to prepared ammonia and other industrial chemical containing nitrogen.
10) Preparation of ammonia:- ammonia can be prepared by Haber's process. In this process pressure of 200*10^5 pa, a temperature of almost equal to 700k, and use catalyst as an iron oxide with a small amount of K2O and Al2O3 to increase the rate of the attainment of equilibrium
11) The nitrogen atom of NH3 has one lone pair of electrons which is available for donation. Hench NH3 reacts as Lewis acid.
12) No2 contains an odd number of valence electrons which behaves as typical odd molecules. On dimerization, it is converted into stable N2O4 molecules with an even number of electrons.
13) Nitric acid preparation:- Nitric acid is prepared by heating with KNO3 and NaNO3 and concentrated H2SO4.
On large scale, it is prepared by the Ostwald process. This process is based upon the catalyst of oxidation of NH3 by atmospheric oxygen. It is used in the manufacture of ammonium nitrate for fertilizer.
14) White phosphorus:- white phosphorus is a translucent waxy solid. It is insoluble in water but soluble in carbon-disulfide and glows darkly. It is dissolved in boiling NaOH solution in an inert atmosphere giving PH3.
15) Red phosphorus:- Red phosphorus is obtained from white phosphorus by heating it at 573k in an inert atmosphere for several days. It is not soluble in water as well as carbon disulfide. It possesses a grey metallic luster.
16) Black phosphorus: Black phosphorus has two forms alpha phosphorus and Bita phosphorus. Alpha phosphorus is formed by heating red phosphorus in a sealed tube at 803K and Bita phosphorus is formed by heating white phosphorus at 573K under high pressure.
17) Preparation of phosphine:- it Is prepared by reaction with calcium phosphide with water and dilute HCl. In the laboratory, it is prepared by reaction with white phosphorus with concentrated NaOH solution in an inert atmosphere of CO2
Both ph4^+ and NH3 are sp^3 hybridized. In ph4^+, all the orbital’s are bonded but nh3 has one lone pair of electrons. Lone pair- lone pair repulsion is responsible for decreasing the bond angle of Nh3. Pcl3 is hydrolyzed in the presents of moisture giving fumes of HCl.
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