There exist attractive and repulsive forces between atoms. When the two forces a

Question

There exist attractive and repulsive forces between atoms. When the two forces are balanced, the atoms reach their equilibrium separation. The atomic binding energy increases when atoms get closer to each other and decreases when atoms move away from one another.

True ______ or False ______

The directionality of chemical bond favors atoms to achieve a close-packed crystal structure.

True ______ or False ______

The loose-packed atomic planes are characterized with a larger inter-planar spacing than the close-packed ones.

True ______ or False ______

For the same material with allotropic behavior of BCC and FCC, like Fe, it has a larger mass density when it takes a close-packed crystal structure, like FCC, than when it takes a loose-packed crystal structure, like BCC.

True ______ or False ______

For the same material with an allotropic behavior of BCC and FCC, like Fe, the larger interstitial site (tetrahedral) in BCC is larger than the larger interstitial site (octahedral) in FCC.

True ______ or False ______

Explanation / Answer

1. False

The atomic binding energy decreases when atoms get closer to each other (repulsive energy increases) and increases when atoms move away from one another( attractive energy increases).

2. True

Octahedral arrangment gives close packed structure with octahedral void and teterahedral arrangement gives tetrahed void

3. True

The close-packed atomic planes are characterized close inter-planar spacing than the loose packed ones.

4. True

density = mass / volume

In both cases volume is same but mass is different, mass is more as space occupancy in FCC is 74% whereas in BCC it is 68%

Therefor density of FCC is more

5. False

For close packed structure ( BCC and FCC) the number of tetrahedral void is 2n waheres octahedral void is n

where n is number of atoms

but BCC has less number of atoms as its packing effiency is 68% so number of tetrahedral void is less

FCC has more number of atoms as its packing effiency is 74% so number of tetrahedral void is more

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