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Chemistry Class 12 > d & f block > Flashcards

d & f block Flashcards

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1
Q

Why is ns^0-2 written in d orbital valence shell electronic config?

A

Since Pd has 0 e`s in S orbital

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2
Q

What are transition elements?

A

Those which have incompletely filled d-orbitals in ground and excited (oxidation) state

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3
Q

Why are Zn, Cd & Hg not transition metals?

A

They have completely filled d-orbitals even after losing e’s from s orbital

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4
Q

Zn & Hf occur together in nature. Why?

A

Due to same properties like atomic size

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5
Q

All groups have metal behavious except for

A

group 12

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6
Q

When no of unpaired e’s are more, bonding in metal

A

increases

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7
Q

Down the group, atomisation enthalpy

A

increases

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8
Q

what is enthalpy of atomization?

A

Energy needed to break the bond to atoms

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9
Q

Why does atomic size decrease and gradually increase again across the period?

A

Due to shielding effect, nucleus is not able ot hold all e’s

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10
Q

What is lanthanoid contraction?

A

gradual decrease in the atomic and ionic size of lanthanoids with an increase in atomic number

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11
Q

Why is lanthanoid contraction seen in 5d & 6s series & 4d and 5d series?

A

14 e’s offer poor shielding effect from the element Hf which causes decrease in atomic size

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12
Q

Why does density of 3d elements increase from Sc to Zn?

A

Atomic mass increases

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13
Q

Why is ionisation enthalpy for 3d series irregular?

A

Due to irregularity in atomic size, it is lower for Cr due to absence of change in config while Zn has change in 4s config. b

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14
Q

If reduction potential is high, its stabitlity is

A

less in aq solution

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15
Q

Why is Cu1+ less stable than Cu2+?

A

Cu1+ has greater reduction potential and Cu2+ is surrounded by many water molecules due to which hydration enthalpy increases so it is stable

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16
Q

What happens when Cu+ is present in aq. sol?

A

It undergoes oxidation & reduction at the same time called disproportionation rn.

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17
Q

Why does Cu have +ve potential?

A

2nd ionisation enthalpy is very high due to which sum of enthalpies is +ve

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18
Q

Why does Mn show a less tendency to get reduced?

A

After losing 2 e’s, it has stable half filled d orbital and -ve potential

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19
Q

If potential is +ve, it will show more tendency to

A

get reduced

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20
Q

Ni has -ve potential due to

A

high hydration enthalpy

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21
Q

why is there irregularity in potentials?

A

Due to irregularity in sublimation & ionisation enthalpies

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22
Q

The stability of divalent ions decrease. Why?

A

Since the potentials are becoming less -ve across the period.

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23
Q

Why is Mn2+ resistant to oxidation but Fe2+ is not?

A

Due to half filled orbitals in Mn2+

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24
Q

Why is reduction potential of Mn3+ high?

A

It is easy for Mn3+ to gain 1 e’ to be stable

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25
Q

Co3+ & Mn3+ are ________ agents

A

oxidising

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26
Q

Ti2+, Cr2+ & V2+ are __________ agents

A

reducing

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27
Q

Which elements doesn’t react with dilute acids at room temp?

A

Ti & V

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28
Q

Why Cu will not react with acid to liberate H2?

A

It has +ve potential

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29
Q

Which only shows +1 state?

A

Cu

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30
Q

Which shows max oxidation states?

A

Mn

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31
Q

Why transition elements show variable oxidation states?

A

(n-1)d and ns e’s are involved in bond formation, pairing of e’s takes place

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32
Q

Why does Mn show many oxidation states?

A

Due to 5 unpaired e’s in ‘d’ & 2 in ‘s’

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33
Q

Commonly seen oxidation state in group 15 elements

A

+3 & +5

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34
Q

Why does +3 stability increase down the group?

A

Due to inert pair effect where nucleus holds e’s in s orbitals which causes increase in nuclear charge & reluctance in bond formation of e’s

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35
Q

Which oxidation state is stable for p block?

A

lower

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36
Q

Which oxidation state is stable for d block?

A

higher

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37
Q

For Mo & W, which is stable?

A

+6

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38
Q

Why does K2Cr2O7 act as good oxidising agent?

A

Since it is stable when it gets reduced to +3 state

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39
Q

Why are MoO3 & WO3 not good oxidising agents?

A

They are already stable in +6 state so they don’t show a tendency to get reduced

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40
Q

Lowest state seen in 3d series

A

0 in the compound [Ni(CO)4]

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41
Q

Highest states are seen in

A

Oxide & flourides

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42
Q

Highest states are seen in oxide & flouride. Why?

A

Due to small sized electro -ve elements, so they are able to oxidise metal to higher state

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43
Q

Why is highest state of an element seen in oxide?

A

Due to ability of oxygen to form multiple bonds with the metal

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44
Q

Which magnetic moment is seen in transition elements?

A

spin

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45
Q

What decides spin MM & color?

A

unpaired e’s

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46
Q

Why are compds formed by Sc3+,Ag+ & Zn2+ colourless?

A

Since they don’t have unpaired e’s

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47
Q

Why are transition elements able to act as catalysts?

A

Since they can show different oxidation states

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48
Q

Why does Pt, Pd & Ni act as catalyst?

A

They have large surface area which provides area for the rn

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49
Q

Why are these elements able to form complexes?

A

Due to small size of ion, high charge of metal ion, availability of empty d orbitals

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50
Q

Interstitial compds?

A

Spaces in b/n atoms in metal lattice which are occupied by small atoms like C, N, H

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51
Q

interstitial compds are _________ compds

A

non-stoichiometric

52
Q

Properties of interstitial compds

A

High MP, hard compds, retain their metallic conductivity, chemically inert

53
Q

Alloys are

A

homogeneous substitutional solid soutions in which some of the metal atoms are replaced by other metals

54
Q

Brass is made of

A

Cu & Zn

55
Q

Bronze is made of

A

Cu & Tin

56
Q

K2Cr2O7 is obtained from

A

Chromite ore when treated with Na2CO3 & O2 & heated

57
Q

To convert chromate to dichromate,

A

acid is added

58
Q

To convert dichromate to chromate,

A

base is added

59
Q

color of (CrO4)2-

A

yellow

60
Q

Color of (Cr2O7)2-

A

orange

61
Q

Effect of H+ on CrO4?

A

It converts it to Cr2O7

62
Q

Why does CrO4 show color despite having unpaired e’s?

A

Due to charge transfer

63
Q

How is KMnO4 obtained?

A

K2MnO4 when kept for some time or when treated with acid give KMnO4

64
Q

Colour of (MnO4)2-

A

green

65
Q

Why does H undergo reduction instead of K+ in KMnO4 formation?

A

Since K+ has -ve potential since it is a metal

66
Q

One property of Kr2CrO7?

A

It is a good oxidising agent in all mediums

67
Q

Why is silver a transition element?

A

d orbitals are completely filled in d^10s^2

68
Q

Why is enthalpy of atomisation lowest for Zn in 3d series?

A

d orbitals are not involved in bonding, so metallic bond is weak and energy to break them to atoms is low

69
Q

how +2 state becomes more stable in 1st half of 3d series with increasing atomic number?

A

the 3d orbitals get gradually occupied and empty orbitals decrease so stability increases from Sc2+ to Mn2+

70
Q

characteristics of d block elements?

A
  1. (n-1)d^1-10 ns^1-2
    metallic lustre, high tensile strength, ductile, malleable
  2. decrease in radius with increasing at. no
  3. Increasing ionisation enthalpy from left to right
  4. Increase in sum of 1st & 2nd ionisation enthalpies
  5. They form complexes
  6. They show dia & para magnetism
  7. Form coloured ions
  8. Used as catalysts
71
Q

Transition elements have _______ electrical & thermal conductivity

A

high

72
Q

Transition elements have ____ volatility

A

low

73
Q

Transition elements have ______ MP

A

high

74
Q

In what way is E.C of these elements different from non-transition elements?

A

In non-transition elements, d orbitals are absent or completely filled

75
Q

Most common states by lanthanoids

A

2, 3 and 4

76
Q

Why transition metals have high enthalpies of atomisation?

A

Due to large no of unpaired e’s. These atoms have strong interatomic interaction & stronger bonding

77
Q

Why do these elements form coloured compds?

A

Due to partial absorption of visible light. The e’ absorbs the radiation of a particular freq & jumps to next orbital

78
Q

How states differ in transition and non transition metals?

A

In non transition metals ,variation is selective ie they differ by 2 and states of transition elements differ by 1

79
Q

Effect of increase in pH on K2Cr2O7

A

It changes to K2Cr2O4(orange to yellow)

80
Q

Examples of disproportionation rns?

A
  1. 3MnO4 + 4H –> 2MnO4 + MnO2 + 2H2O
  2. 3CrO4 + 8H –> 2crO4 + Cr3+ + 4H2O
81
Q

Example for lowest oxide is basic, highest oxide is acidic/amphoteric

A

MnO(Mn2+) ; Mn2O7(Mn7+)

82
Q

Alloy which contains lanthanoid metals

A

mischmetal which has S, C, Ca & Al

83
Q

Use of mischmetal

A

Produce bullets, shell & lighter flint

84
Q

Elements of 1st series posess diff properties than those of heavier elements?

A

Due to larger atomic radii of heavier elements, high ionization and atomisation enthalpy, higher MP & BP

85
Q

Ce exhibit

A

+4

86
Q

Pr exhibit

A

+4

87
Q

Tb exhibit

A

+4

88
Q

Nd exhibit

A

+2

89
Q

Sm & Eu exhibit

A

+2

90
Q

Electronic COnfig for lanthanoids

A

[Xe]4f^1-14 5d^0-1 6s^2

91
Q

Electronic Config for actinoids

A

[Rn]5f^1-14 6d^0-1 7s^2

92
Q

Most stable state for lanthanoid

A

+3. Some show 2 & 4

93
Q

Most stable state for actinoids

A

Besides three, 4,5,6, & 7 are seen

94
Q

Reactivity of lanthanoids

A

Less reactive metals

95
Q

Reactivity of actinoids

A

More reactive

96
Q

Which doesn’t form oxocations?

A

Lanthanoids

97
Q

Which forms complexed easily?

A

Actinoids

98
Q

________ compds are less basic

A

lanthanoid

99
Q

Which CuX2 will not be formed?

A

CuI2

100
Q

As size of ion increases, its covalent nature

A

decreases

101
Q

Why are Yb2+ & Eu2+ good reducing agents?

A

it will try to go to its stable +3 state and get oxidised

102
Q

Why are Ce +4 & Tb 4+ good oxidising agents?

A

They show tendency to get reduced to +3 state to be stable

103
Q

The only radioactive element in lanthanoids

A

Promethium(Pm)

104
Q

Which has highest MP in lanthanoids?

A

Samarium(Sm) 1623K

105
Q

Lanthanoids are good _______ agents

A

reducing

106
Q

Lanthanoids have __ potential values

A

-ve

107
Q

Most stable state in Lanthanoids

A

+3

108
Q

Why is +2 state also shown by lanthanoids?

A

Stable half or filled orbitals

109
Q

Atomic size _____ with increase in atomic no. due to poor shielding effect

A

decrease

110
Q

Basic strength of hydroxides of lanthanoids

A

Decreases from Ce to Lu

111
Q

Why does covalent nature increase when size of ion decrease?

A

When size is less, +ve ion will have greater polarising power to capture the e’ cloud of the anion due to which OH cannot be given easily(Fajan’s rules). So basicity decreases.

112
Q

Does lanthanides show color & paramagnetism?

A

Yes

113
Q

lanthanoids have spin &

A

orbital magnetic moment

114
Q

Lanthanoid + H2O gives

A

LnOH3 + H2(displaces H)

115
Q

uses of Lanthanoids

A
  1. Oxides are used as catalysts in cracking of petroleum
  2. Oxide used to make Crook’s lens for protection from UV rays
  3. Making Mischmetal
116
Q

Pyrophoric alloy

A

Mischmetal + magnesium

117
Q

Why is pyrophoric alloy used for making bullets?

A

It catches fire easily

118
Q

Actinoid contraction

A

Poor shielding effect of 5f e’s

119
Q

Why lanthanoids have greater ionisation energy than actinoids?

A

4f is near to nucleus than 5f so it can pull the e’s more than those of 5f

120
Q

Why does actinides show more oxidation states?

A

Less diff in energy b/n 5f 6d 7s

121
Q

Mn2O7 is acidic where MnO is basic

A

Mn has +7 in Mn2O7 which is more acidic

122
Q

Acidic nature increase on _____ in oxidation states

A

Increasing

123
Q

d block elements exhibit more oxidatoin states than f block

A

Less energy diff b/n d & s orbitals in d block

124
Q

Zr & Hf have similar atomic radii

A

Lanthanoid contraction

125
Q

Titration of FeSO4 with KMnO4 uses dil H2SO4 & not dil HCl. Why?

A

Chlorine produces greenish yellow gas which interrupts pale pink colour needed.

126
Q

Co2+ is easily oxidised in presence of strong ligands

A

Co 2+ will easily lose 1 e’ to be stable

127
Q

Transition elements have high enthalpy of atomisation. Why?

A

Due to strong metallic bonding due to unpaired e’s

Chemistry Class 12 (10 decks)

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