Coordination number in a square close packed structure and hexagonal close packed structure respectively are

Options

A. `6,4`
B. `2,6`
C. `3,6`
D. `4,6`

Answer

d

Explanation

Close packing in two - dimensions can be

Type `1A A A……` type
The second row may be palced in contact with the firse such that the sphere of the second of the second row are electly above these of the first row .The sphere of the two row are aligmed horizontally as well as vertically of this arrangement , each sphere is in contact with four of the reighhours.
Thus, its coordination number `= 4` and is called spahere close packing in two - dimensions.
Atoms `(A)` is in contact with four others
Type II `ABAB......`type
The second row may be pleced above the first in a staggeened number such that its sphere fit in the depressions of the first rows
First row arrangement A type
second row arrangement B type
Third row arrangement A type and so on
There is less free space and packing is move effective than the squre close packing Each spahere is in contact with six of its neighours and connection number `= 4` an two dimension it is called two dimensional basagonal is shape packing voids formad is this case are trangular in shape if tghe spex of the trangular downward in the first row .it upward in the second row