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

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Solution

(a,d)

When KCI crystals are heated it leads the deposition of potassium ion on the surface of KCI. The $C I^{-}$ ions diffuse to the surface of crystal and loss electron by potassium atom to form $K^{+}$ ion released electron occupied anionic site which is known as F-centre and impart colour to the crystal.

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Q. The anionic sites occupied by unpaired electrons are called F-centers or colour centers. They impart ______

(X)

colour to the crystals on

N a C l .

Excess of lithium makes

L i C l

crystals ______

(Y)

and excess of potassium makes

K C l

crystals ______

(Z)

(X)

(Y)

and

(Z)

are:

Schottky defect is observed in crystals when .....................

(a) some cations move from their lattice site to interstitial sites

(b) equal number of cation and anions are missing from the lattice

(d) some impurity is present in the lattice

Q. An excess of potassium ions makes KCl crystals appear violet or Lilac in colour since

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?

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

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(a,d) When KCI crystals are heated it leads the deposition of potassium ion on the surface of KCI. The CI− ions diffuse to the surface of crystal and loss electron by potassium atom to form K+ ion released electron occupied anionic site which is known as F-centre and impart colour to the crystal.