The combining capacity of an element is called valency. The valence electrons determine the combining capacity of an atom. The number of bonds that an atom can form as part of a compound is expressed by the valency of the element. For example- The valency of hydrogen is 1, oxygen is 2, carbon is 4, etc.

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Classify the following ions into monovalent, divalent and trivalent.
${Ni}^{2 +}, {Fe}^{3 +}, {Cu}^{2 +}, {Ba}^{2 +}, {Cs}^{+}, {Zn}^{2 +}, {Cd}^{2 +}, {Hg}^{2 +}, {Pb}^{2 +}, {Mn}^{2 +}, {Fe}^{2 +}, {Co}^{2 +}, {Sr}^{2 +}, {Cr}^{3 +}, {Li}^{+}, {Ca}^{2 +}, {Al}^{3 +}$

Important Questions on Atoms and Molecules

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An intrinsic semiconductor is converted into

n

-type extrinsic semiconductor by doping it with:-

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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?

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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Glass 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 _____.

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

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

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Silicon doped with gallium forms

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Valence electron in

{Cl}^{-}

ions 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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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 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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Which of the following oxides shows electrical properties like metals?

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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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The pair of valencies exhibited by tin

(Sn)

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Define valency.

Classify the following ions into monovalent, divalent and trivalent. Ni2+, Fe3+, Cu2+, Ba2+, Cs+, Zn2+, Cd2+, Hg2+, Pb2+, Mn2+, Fe2+, Co2+, Sr2+, Cr3+, Li+, Ca2+, Al3+

Important Questions on Atoms and Molecules

Learn and Prepare for any exam you want !

Classify the following ions into monovalent, divalent and trivalent.
${Ni}^{2 +}, {Fe}^{3 +}, {Cu}^{2 +}, {Ba}^{2 +}, {Cs}^{+}, {Zn}^{2 +}, {Cd}^{2 +}, {Hg}^{2 +}, {Pb}^{2 +}, {Mn}^{2 +}, {Fe}^{2 +}, {Co}^{2 +}, {Sr}^{2 +}, {Cr}^{3 +}, {Li}^{+}, {Ca}^{2 +}, {Al}^{3 +}$