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The Solid State

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Chemistry I

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Classify each of the following as being either a p-type or an n-type semi conducor:
(i) Ge doped with In
(ii) B doped with Si.

(i) Ge is an element of 14th group (like Si) and has configuration 4s24p2. It has been doped with In, a 13th group element having 5s25p1 configuration i.e., element of 14th group has been doped with 13th group element. All three valence electrons of impurity atom (In) gets bonded with three out of four eectrons of Ge and one electron of Ge remains unbonded. Conductivity is due to unbonded electron of insulator, Ge. Therefore, it is a p-type semi-conductor.

(ii) Boron, B is an element of 13th group and has 2s22p1 configuration. It is doped with Si, an element of 14th group having 3s23p2 configuration. All three electrons of boron gets bonded with 3 out of 4 electrons of Si and 4th electron of impurity atom (i.e., Si) is responsible for conductivity. Thus it is a n-type semiconductor.


Why do solids have a definite volume?

A solid have a definite volume because the inter molecular distance  between its molecules are fixed.

Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show clevage property?

Refractive index of a solid which have the same value along all directions are isotropic in nature. It would not show cleavage property.

Why is glass considred a super-cooled liquid?

Glass is amorphous solids and  have a tendency to flow, though very slowly. Therefore, these are called pseudo solids or super cooled liquids .

Classify the following as amorphous or crystalline solids: Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.

Amorphous solids: Polyurethane, teflon, cellophane, polyvinyal chloride, fibre glass.
Crystalline solids: naphthlene, benzoic acid, potassium nitrate, copper.

Why are solids rigid?

Solids are rigid because the internuclear distance between the  molecules of a solid are very less and closely packed and their positions are fixed due to the strong forces of attraction between them.