An element has a body-centered cubic (BCC) structure with a cell edge of 288 pm. The atomic radius is:

1. 24×288 pm

2. 43×288 pm

3. 42×288 pm

4. 34×288 pm

Subtopic:  Introduction & Crystal System | Density & Packing Fraction |
 81%
From NCERT
NEET - 2020
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The crystal with a metal deficiency defect is - 

1. NaCl 

2. FeO

3. ZnO 

4. KCl

Subtopic:  Imperfections in Solids & Semiconductors |
 72%
From NCERT
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The electrical conductivity of semiconductors increases with a rise in temperature because:

1. Electrons jump from the valence band to the conduction band.
2. Electrons jump from the conduction band to the valence band.
3. No electrons jump from the valence band to the conduction band.
4. No electrons jump from the conduction band to the valence band.

Subtopic:  Magnetic Behaviour of an Element/Compound |
 82%
From NCERT
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Select the correct option based on statements below:

Assertion (A): The stability of a crystal is reflected by the magnitude of its melting point.
Reason (R): Greater the intermolecular forces of attraction, the higher will be the stability and melting point of the substance.
 
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. Both (A) and (R) are false.
Subtopic:  Introduction & Crystal System |
 87%
From NCERT
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The packing efficiency of the face-centered cubic unit cell is:
(assuming that the atoms are touching each other)

1. 52.40 %

2. 68.04 %

3. 74 %

4. 79.06 %

Subtopic:  Density & Packing Fraction |
 85%
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Copper crystallizes into an fcc lattice with an edge length of 3.61 × 10−8 cm. The density of copper crystal will be - 

1. 7.46 g cm-3

2. 9.67 g cm-3

3. 8.96 g cm-3

4. 5.63 g cm-3

Subtopic:  Density & Packing Fraction |
 50%
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A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1/3rd of tetrahedral voids. The formula of the compound would be -

1. MN

2. M3N4

3. M2N3

4. M3N2

Subtopic:  Voids, Radius Ratio & Coordination Number |
 76%
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Select the correct option based on statements below:

Assertion (A): Ferromagnetic solids become paramagnetic upon heating.
Reason (R): Unpaired electrons starts pairing upon heating.
 
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. Both (A) and (R) are false.
Subtopic:  Magnetic Behaviour of an Element/Compound |
From NCERT
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The incorrect statement among the following regarding crystalline solid is -

1. Definite and characteristic heat of fusion.
2. Isotropic nature.
3. A regular periodically repeated pattern of arrangement of constituent particles in the entire crystal.
4. A true solid.

Subtopic:  Introduction & Crystal System |
 84%
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An example of amorphous solid among the following is -

1. Graphite (C)

2. Quartz glass (SiO2)

3. Chrome alum

4. Silicon carbide (SiC)

Subtopic:  Introduction & Crystal System |
 76%
From NCERT
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