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Crystals have vacant sites or defects in...

Crystals have vacant sites or defects in them. When light strikes a photographic AgBr paper, silver atoms move in through these defects to:

A

Form negative images

B

Form tiny clumps of silver atoms

C

Form a coloured image

D

None of these

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To solve the question regarding the behavior of silver atoms in photographic AgBr paper when exposed to light, we can break down the process step by step: ### Step-by-Step Solution: 1. **Understanding the Composition of AgBr Paper**: - Photographic AgBr paper consists of silver bromide (AgBr) crystals, which contain silver ions (Ag⁺) and bromide ions (Br⁻). These crystals may have defects or vacant sites. **Hint**: Recall that AgBr is a compound made of silver and bromine, and it forms a crystalline structure. 2. **Effect of Light on AgBr Paper**: - When light strikes the AgBr paper, it provides energy to the electrons in the crystal lattice. This energy is sufficient to excite some electrons. **Hint**: Think about how light interacts with materials and what happens at the atomic level when energy is absorbed. 3. **Excitation of Electrons**: - The absorbed energy causes some electrons to become energetic. These energetic electrons can then interact with the silver ions present in the crystal. **Hint**: Consider the role of energy in facilitating electron transitions and interactions in a crystal lattice. 4. **Reduction of Silver Ions**: - The energetic electrons collide with the silver ions (Ag⁺), reducing them to neutral silver atoms (Ag). This process is known as reduction. **Hint**: Remember that reduction involves the gain of electrons, which is happening to the silver ions in this case. 5. **Movement of Silver Atoms**: - The newly formed silver atoms can then migrate through the vacant sites or defects in the crystal lattice. This migration leads to the formation of tiny clusters of silver atoms. **Hint**: Think about how defects in a crystal can facilitate the movement of atoms or ions. 6. **Color Change in the Photographic Paper**: - The silver atoms that form are black in color. As a result, when light strikes the AgBr paper and silver ions are converted to silver atoms, the paper darkens, creating an image. **Hint**: Consider how the color of a material can change based on the presence of different phases or species. 7. **Conclusion**: - The overall process results in the photographic paper turning black due to the formation of metallic silver, which is a crucial step in developing photographic images. **Hint**: Summarize the entire process to understand the final outcome of the interaction between light and AgBr paper. ### Final Answer: When light strikes a photographic AgBr paper, silver atoms move in through these defects to form tiny clusters of silver atoms, resulting in a blackened image due to the formation of metallic silver.
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Assertion (A) : Non-stoichiometric compounds are called Bertholide compounds. NaCl and KCl crystal, when heated in an atmosphere of Na and K varpours, respectively, they impart violet and yellow colours to NaCl and KCl , respectively. Reason (R ) : Metal excess defect is due to the presence of extra cations atg the interstitial sites. The excess metal ions move to the interstitial sites and the electrons to the neighbouring sites. The colour results byt the excitation of these electrons by absorbing suitable energy from visible light. When the excited electroon comes back to the ground state, there is emission of radiation in the visible region and gives complimentary colour.

In a ideal crystal there nust be regular repeating arrangement of the constuting particles and its entropy must be zero at absolute zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal these defects arise either due to disorder or dislocation of the movement of the particles even at absolute zero temperature. Such defect increases with rise in temperature. In addition ti this, certain defects arise due to the pressure of some impurities. Such defects not only modify the existing properties of the crystalline solid but also impart certain new characteritics to them. In pure crystal, e.g, silicon or germanium at 0K, the electrons are prsent in fully occupied lowest energy states and are not xpected to conduct any electricity. However at temperature above 0K, some electron leave their bonds and become free to move in the crystal lattice, giving rise to and become free to move in the crystal lattice, giving rise to electrical conductivity. The electron deficient bonds, called holes (+vely charged) and thermally mobile electrons move in opposite direction under the electric field. Stoichiometric ppoint defects include (a) Schottky defects, which arise due to missing of both cations and anions from their lattice sites without disturbing the stoichiometry and (b) Frenked defects, which arise due to misplacement of certian ions in the crystal lattice. The former defect gives rise to no change of density. Another type of defects are non-stoichometry defects where the cetions and anion are not present in the stoichiometry ratio. In metal excess defect, metal ions or positive ions are in excess as compared to anions of non-metals stoichiometrycally. On the other hand in metal deficiency defect, the cations are in lesser proportion than stoichiometric value. Since the crystal is neutral electrically, the balance of charge is maintained by free electrons or extra positive charges. The metal excess defects gives rise to conduction of electricity due to the presence of free electrons. Also crystals having metal excess defects are paramagnetic and coloured due to the presence of electrons in the anion vacancies. Impurity defects arise when some foreign atoms are present at the lattice sites in place of the host atoms or at the vacant interstitial sites. When 15 group elements like P or are doped into Si or Ge, the added impurity atoms occupy the lattice sites forming four covalent bonds with 4 Si/Ge atoms leaving an extra electron free to move. Such a crystal is said to be n-type semi conductor because the conduction of electricity is due to movement of extra unbounded electrons. If doping of a covalent crystal of 14 group elements are caused by addition of small amounts of elements are caused by addition of small amounts of elements of group 13, e.g, Al or Ga with three valence electrons, one covalent bond formed will be electron deficient and acts as a positive hole. The presence of such holes in the crystal leads to electrical conductivity and the the crystal is said to be p-type semiconductor. Lattice defect per 10^(15)NaCl is 1. What is the number of lattice defects in 1 mole of NaCl?

In a ideal crystal there nust be regular repeating arrangement of the constuting particles and its entropy must be zero at absolute zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal these defects arise either due to disorder or dislocation of the movement of the particles even at absolute zero temperature. Such defect increases with rise in temperature. In addition ti this, certain defects arise due to the pressure of some impurities. Such defects not only modify the existing properties of the crystalline solid but also impart certain new characteritics to them. In pure crystal, e.g, silicon or germanium at 0K, the electrons are prsent in fully occupied lowest energy states and are not xpected to conduct any electricity. However at temperature above 0K, some electron leave their bonds and become free to move in the crystal lattice, giving rise to and become free to move in the crystal lattice, giving rise to electrical conductivity. The electron deficient bonds, called holes (+vely charged) and thermally mobile electrons move in opposite direction under the electric field. Stoichiometric ppoint defects include (a) Schottky defects, which arise due to missing of both cations and anions from their lattice sites without disturbing the stoichiometry and (b) Frenked defects, which arise due to misplacement of certian ions in the crystal lattice. The former defect gives rise to no change of density. Another type of defects are non-stoichometry defects where the cetions and anion are not present in the stoichiometry ratio. In metal excess defect, metal ions or positive ions are in excess as compared to anions of non-metals stoichiometrycally. On the other hand in metal deficiency defect, the cations are in lesser proportion than stoichiometric value. Since the crystal is neutral electrically, the balance of charge is maintained by free electrons or extra positive charges. The metal excess defects gives rise to conduction of electricity due to the presence of free electrons. Also crystals having metal excess defects are paramagnetic and coloured due to the presence of electrons in the anion vacancies. Impurity defects arise when some foreign atoms are present at the lattice sites in place of the host atoms or at the vacant interstitial sites. When 15 group elements like P or are doped into Si or Ge, the added impurity atoms occupy the lattice sites forming four covalent bonds with 4 Si/Ge atoms leaving an extra electron free to move. Such a crystal is said to be n-type semi conductor because the conduction of electricity is due to movement of extra unbounded electrons. If doping of a covalent crystal of 14 group elements are caused by addition of small amounts of elements are caused by addition of small amounts of elements of group 13, e.g, Al or Ga with three valence electrons, one covalent bond formed will be electron deficient and acts as a positive hole. The presence of such holes in the crystal leads to electrical conductivity and the the crystal is said to be p-type semiconductor. The type of semiconduction shown by crystal capable of showing Schottky defect, will be :

In a ideal crystal there nust be regular repeating arrangement of the constuting particles and its entropy must be zero at absolute zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal these defects arise either due to disorder or dislocation of the movement of the particles even at absolute zero temperature. Such defect increases with rise in temperature. In addition ti this, certain defects arise due to the pressure of some impurities. Such defects not only modify the existing properties of the crystalline solid but also impart certain new characteritics to them. In pure crystal, e.g, silicon or germanium at 0K, the electrons are prsent in fully occupied lowest energy states and are not xpected to conduct any electricity. However at temperature above 0K, some electron leave their bonds and become free to move in the crystal lattice, giving rise to and become free to move in the crystal lattice, giving rise to electrical conductivity. The electron deficient bonds, called holes (+vely charged) and thermally mobile electrons move in opposite direction under the electric field. Stoichiometric ppoint defects include (a) Schottky defects, which arise due to missing of both cations and anions from their lattice sites without disturbing the stoichiometry and (b) Frenked defects, which arise due to misplacement of certian ions in the crystal lattice. The former defect gives rise to no change of density. Another type of defects are non-stoichometry defects where the cetions and anion are not present in the stoichiometry ratio. In metal excess defect, metal ions or positive ions are in excess as compared to anions of non-metals stoichiometrycally. On the other hand in metal deficiency defect, the cations are in lesser proportion than stoichiometric value. Since the crystal is neutral electrically, the balance of charge is maintained by free electrons or extra positive charges. The metal excess defects gives rise to conduction of electricity due to the presence of free electrons. Also crystals having metal excess defects are paramagnetic and coloured due to the presence of electrons in the anion vacancies. Impurity defects arise when some foreign atoms are present at the lattice sites in place of the host atoms or at the vacant interstitial sites. When 15 group elements like P or are doped into Si or Ge, the added impurity atoms occupy the lattice sites forming four covalent bonds with 4 Si/Ge atoms leaving an extra electron free to move. Such a crystal is said to be n-type semi conductor because the conduction of electricity is due to movement of extra unbounded electrons. If doping of a covalent crystal of 14 group elements are caused by addition of small amounts of elements are caused by addition of small amounts of elements of group 13, e.g, Al or Ga with three valence electrons, one covalent bond formed will be electron deficient and acts as a positive hole. The presence of such holes in the crystal leads to electrical conductivity and the the crystal is said to be p-type semiconductor. In the crystal of Fe_(0.93) O, the percentage of Fe(III) will be:

In a ideal crystal there nust be regular repeating arrangement of the constuting particles and its entropy must be zero at absolute zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal these defects arise either due to disorder or dislocation of the movement of the particles even at absolute zero temperature. Such defect increases with rise in temperature. In addition ti this, certain defects arise due to the pressure of some impurities. Such defects not only modify the existing properties of the crystalline solid but also impart certain new characteritics to them. In pure crystal, e.g, silicon or germanium at 0K, the electrons are prsent in fully occupied lowest energy states and are not xpected to conduct any electricity. However at temperature above 0K, some electron leave their bonds and become free to move in the crystal lattice, giving rise to and become free to move in the crystal lattice, giving rise to electrical conductivity. The electron deficient bonds, called holes (+vely charged) and thermally mobile electrons move in opposite direction under the electric field. Stoichiometric ppoint defects include (a) Schottky defects, which arise due to missing of both cations and anions from their lattice sites without disturbing the stoichiometry and (b) Frenked defects, which arise due to misplacement of certian ions in the crystal lattice. The former defect gives rise to no change of density. Another type of defects are non-stoichometry defects where the cetions and anion are not present in the stoichiometry ratio. In metal excess defect, metal ions or positive ions are in excess as compared to anions of non-metals stoichiometrycally. On the other hand in metal deficiency defect, the cations are in lesser proportion than stoichiometric value. Since the crystal is neutral electrically, the balance of charge is maintained by free electrons or extra positive charges. The metal excess defects gives rise to conduction of electricity due to the presence of free electrons. Also crystals having metal excess defects are paramagnetic and coloured due to the presence of electrons in the anion vacancies. Impurity defects arise when some foreign atoms are present at the lattice sites in place of the host atoms or at the vacant interstitial sites. When 15 group elements like P or are doped into Si or Ge, the added impurity atoms occupy the lattice sites forming four covalent bonds with 4 Si/Ge atoms leaving an extra electron free to move. Such a crystal is said to be n-type semi conductor because the conduction of electricity is due to movement of extra unbounded electrons. If doping of a covalent crystal of 14 group elements are caused by addition of small amounts of elements are caused by addition of small amounts of elements of group 13, e.g, Al or Ga with three valence electrons, one covalent bond formed will be electron deficient and acts as a positive hole. The presence of such holes in the crystal leads to electrical conductivity and the the crystal is said to be p-type semiconductor. Which of the following statements is correct about the conduction of electricity in pure crystal of silicon at room temperature?