Q3 of 36 Page 1

Why conductivity of silicon increases on doping with phosphorus?

Silicon has four valence electrons. When a silicon atom is replaced with phosphorus with 5 valence electrons atom, it can share one electron with each of the four silicon atoms surrounding it. This leaves the fifth valence electron of phosphorus free to move. Hence doping of silicon with phosphorus atom induces conductivity in silicon. Such type of doping is called n-type doping.


More from this chapter

All 36 →
26

(a) How do you convert the following :

(i) Phenol to Anisole


(ii) Ethanol to Propan-2-ol


(b) Write mechanism of the following reaction :



(c) Why phenol undergoes electrophilic substitution more easily than benzene ?


OR


(a) Account for the following :


(i) o-nitrophenol is more steam volatile than p-nitrophenol.


(ii) t-butyl chloride on heating with sodium methoxide gives 2-methylpropene instead of t-butylmethylether.


(b) Write the reaction involved in the following :


(i) Reimer-Tiemann reaction


(ii) Friedal-Crafts Alkylation of Phenol


(c) Give simple chemical test to distinguish between Ethanol and Phenol.


 27

(a) Give reasons for the following :

(i) Sulphur in vapour state shows paramagnetic behaviour.


(ii) N-N bond is weaker than P-P bond.


(iii) Ozone is thermodynamically less stable than oxygen.


(b) Write the name of gas released when Cu is added to


(i) dilute HNO3 and


(ii) conc. HNO3


OR


(a) (i) Write the disproportionation reaction of H3PO3.


(ii) Draw the structure of XeF4.


(b) Account for the following :


(i) Although Fluorine has less negative electron gain enthalpy yet F2 is strong oxidizing agent.


(ii) Acidic character decreases from N2O3 to Bi2O3 in group 15.


(c) Write a chemical reaction to test sulphur dioxide gas. Write chemical equation involved.


5

Write IUPAC name of the given compound:


 8

Write two differences between an ideal solution and a non-ideal solution.