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Assertion: Every 4th layer is identical ...

Assertion: Every 4th layer is identical to first layer in ccp pattern of three dimension arrangement
Reason: ABCABC…. Arrangement is present in ccp

A

If both assertion and reason are correct and reason is correct explanation for assertion

B

If both assertion and reason are correct but reason is not correct explanation for assertion

C

If assertion is correct but reason is incorrect

D

If both assertion and reason are incorrect

Text Solution

Verified by Experts

The correct Answer is:
A
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Iron crystallises into a crystal structure in which the layer of Fe atoms form close-packed arrangement with stacking sequence ABCABC… . What is this close-packed arrangement called? How many Fe atoms are there in the unit cell of Fe crystal?

In a hexaonal system system of cycstals, a frequently encountered arrangement of atoms is described as a hexagonal prism. Here, the top and bottom of the cell are refular hexagons, and three atoms are sandwiched in between them. A space-cilling model of this structure, called hexagonal close-paked is constituted of a sphere on a flat surface surrounded in the same plane by six identical spheres as closely as possible. Three spherres are then placed overt the first layer so that they toych each other and represent the second layer so that they toych each other and present the second layer. Each one of the three spheres touches three spheres of the bottom layer. Finally, the second layer is convered with a third layer identical to the bottom layer in relative position. Assume the radius of every sphere to be r . The empty space in this hcp unit cell is

Packing refers to the arrangement of constituent units in such a way that the forces of attraction among the constituent particles is the maximum and the contituents occupy the maximum available space. In two dimensions, there are hexagonal close packing and cubic close packing. In three dimentions, there are hexagonal, cubic as well as body centred close packings. A certain oxide of a metal M crystallises in such a way that O^(2-) ions occupy hcp arrangement following ABAB... pattern. The metal ions however occupy 2//3 rd of the octahedral voids. The formula of the compound is :

In a hexaonal system system of cycstals, a frequently encountered arrangement of atoms is described as a hexagonal prism. Here, the top and bottom of the cell are refular hexagons, and three atoms are sandwiched in between them. A space-cilling model of this structure, called hexagonal close-paked is constituted of a sphere on a flat surface surrounded in the same plane by six identical spheres as closely as possible. Three spherres are then placed overt the first layer so that they toych each other and represent the second layer so that they toych each other and present the second layer. Each one of the three spheres touches three spheres of the bottom layer. Finally, the second layer is convered with a third layer identical to the bottom layer in relative position. Assume the radius of every sphere to be r . The number of atom in this hcp unit cell is

In hexagonal systems of crystals, a frequently encountered arrangement of atoms is described as a hexagonal prism. Here, the top and bottom of the cell are regular hexagons and three atoms are sandwiched in between them. A space-filling model of this structure, called hexagonal close-packed (HCP), is constituted of a sphere on a flat surface surrounded in the same plane by six identical spheres as closely as possible. Three spheres are then placed over the first layer so that they touch each other and represent the second layer. Each one of these three spheres touches three spheres of the bottom layer. Finally, the second layer is covered with a third layer that is identical to the bottom layer in relative position. Assume radius of every sphere to be ‘r’. The volume of this HCP unit cell is

Assertion (A) : Presently, the global atmosphere is warming up. Reason (R): The depletion of stratospheric ozone layer has resulted in increase in ultraviolet radiations reaching the Earth.

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Packing refers to the arrangement of constituent units in such a way that the forces of attraction among the constituent particles is the maximum and the contituents occupy the maximum available space. In two dimensions, there are hexagonal close packing and cubic close packing. In three dimentions, there are hexagonal, cubic as well as body centred close packings. The pattern of successive layers in ccp arrangement is:

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