Metal Excess Defect
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In metal excess defect, anions all missed from their lattice sites and they are occupied by electrons to maintain electrical neutrality. These sites occupied by electrons are called F-centers.
What is the effect of metal excess defect on density of the crystal?
Increases
Does Not have any effect
Decreases
- Decreases, then increases
Paragraph :In metal excess defect, anions all missed from their lattice sites and they are occupied by electrons to maintain electrical neutrality. These sites occupied by electrons are called F-centers.
Question: The colour of NaCl changes when heated in sodium vapour due to
Excess of sodium in the crystal
Electrons in the voids
Excess of chlorine in the crystal
Deficiency of sodium in the crystal
Paragraph :In metal excess defect, anions all missed from their lattice sites and they are occupied by electrons to maintain electrical neutrality. These sites occupied by electrons are called F-centers.
Question: In metal excess defect
anions miss from their lattice points
Cations miss from their lattice points
Both cations and anions miss from their lattice points
Extra anions are doped
Reason: Electrons trapped in anion vacancies are referred to as F-centers.
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The apperance of colour in solid alkali metal halides is generally due to
Interstitial positions
F- center
Frenkel defect
Schottky defect
- Metal excess defect
- Scottky defect
- Metal deficiency defect
- Vacancy defect
- A compound resembling cement
- An alloy of Fe and Cr
- Interstitial compound of iron and carbon
- An ore of iron
Those elements impart colour to the flame on heating in it, the atoms of which require the low energy of the ionization (i.e., absorb energy in group visible region of the spectrum). The elements of which of the following groups will impart colour to the flame?
(a) 2 (b) 13 (c) 1 (d) 17
An excess of potassium ions makes KCL crystals appear violet or lilac colour since ................
(a) some of the anionic sites are occupied by an unpaired electron
(b) some of the anionic sites are occupied by a pair of electrons
(c) there are vacancies at some anionic sites
(d) F-centres are created which impart colors to the crystals
Why does table salt, NaCl sometimes appear yellow in colour?