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Why do some elements form diatomic or triatomic molecules?

Important Questions on Atoms and Molecules

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Glass is

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An intrinsic semiconductor is converted into

n

-type extrinsic semiconductor by doping it with:-

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In the following circuit diagram, the current through the battery is

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Match the following

List - I List-II
A) Metallic solid I) Carbon tetrachloride
B) Covalent solid II) Calcium fluoride
C) Molecular solid III) Copper
D) Ionic solid IV) Silicon carbide
V) Glass

The correct answer is

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The radius of

K^{+}

133 pm

and that of

{Cl}^{-}

181 pm

. The volume of the unit cell of

KCl

expressed in

10^{- 22} {cm}^{3}

is:

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Which among the following is NOT a polar molecular solid ?

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Among the following, which have highest melting point?

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Which of the following is not a conductor of electricity?

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The barrier potential of a p-n junction depends on:

(a)

type of semi-conductor material

(b)

amount of doping

(c)

temperature
Which one of the following is correct?

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The contribution to the total current in a semiconductor, due to electrons and holes are

0.75

and

0.25

respectively. The drift velocity of electrons is

\frac{3}{2}

times that of holes at this temperature. Then the ratio between electron concentration and hole concentration is

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A compound formed by elements

X

and

Y

crystallises in the cubic structure, where

X

atoms are at the corners of a cube and

Y

atoms are at the centre of the body. The formula of the compounds is

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In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion

(C a^{2 +})

and fluoride ion

(F^{-})

are

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Which of the following oxides shows electrical properties like metals?

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Silicon doped with gallium forms

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The density of an electron-hole pair in pure germanium is

3 \times 10^{16} m^{- 3}

at room temperature. On doping with aluminium, the hole density increases to

4.5 \times 10^{22} m^{- 3}

. Now the electron density (in

m^{- 3}

) in doped germanium will be

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______ solids are formed by the three-dimensional arrangements of cations and anions bound by strong Coulombic (electrostatic) forces

.

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A hard substance melts at high temperature and is an insulator in both solid and in molten state.
This solid is most likely to be a / an :

HARD

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The cubic unit cell structure of a compound containing cation $M$ and anion $X$ is shown below. When compared to the anion, the cation has smaller ionic radius. Choose the correct statement(s).

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A unit cell of calcium fluoride has four calcium ions. The number of fluoride ions in the unit cell is

HARD

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Consider an ionic solid

MX

, with

NaCl

structure. Construct a new structure

(Z)

, whose unit cell is constructed from the unit cell of

MX

, following the sequential instructions given below. Neglect the charge balance.

(i)

Remove all the anions

(X)

, except the central one.

(ii)

Replace all the face centered cations

(M)

, by anions

(X)

(iii)

Remove all the corner cations

(M)

(iv)

Replace the central anion

(X)

, with cation

(M)

.

The value of

(\frac{n u m b e r o f a n i o n s}{n u m b e r o f c a t i o n s})

Z

is _____.

Why do some elements form diatomic or triatomic molecules?

Important Questions on Atoms and Molecules

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