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Group 13 Flashcards

1
Q

Name elements of Group 13

A

Boron - Aluminum - Gallium - Indium - Thallium - Nihonium

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2
Q

Discuss occurrence of Boron

A
  1. Borax
  2. Orthoboric acid
  3. Kernite
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3
Q

Give formula of borax

A

Na2B4O7.10H2O

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4
Q

Give formula of orthoboric acid

A

H3BO3

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5
Q

Give formula of kernite

A

Na2B4O7.4H2O

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6
Q

Where is borax found in India

A

Sambhar Lake in Rajasthan and Puga Valley in Ladakh

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7
Q

Does boron have isotopes? Discuss

A

Yes, two - B(10) and B(11)

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8
Q

Which isotope of Boron is more abundant

A

B(11) - 81%

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9
Q

Discuss abundancy of Aluminum

A

Most abundant metal

Third most abundant element on the Earth’s crust after oxygen and silicon

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10
Q

Discuss occurrence of Aluminum

A
  1. In Bauxite
  2. In Cryolite
  3. In mica
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11
Q

Give formula of Bauxite

A

Al2O3.2H2O

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12
Q

Give formula of Cryolite

A

Na3AlF6

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13
Q

Where is aluminum found in India

A

As Mica in Madhya Pradesh, Karnataka, Odisha and Jammu

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14
Q

What is the atomic number and mass of Nihonium

A

Nh has atomic number - 113 and atomic mass - 286 g/mol

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15
Q

Is Nh natural? Give its half life

A

Nh is synthetically prepared and radioactive

Its more stable isotope has a half life of 20 seconds

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16
Q

Electronic configuration of group 13

A

ns2np1

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17
Q

Discuss atomic size trend

A

Atomic size increases on going down the group due to increase in number of shells

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18
Q

Discuss exception wrt atomic size

A

Ga has smaller size than Al because Ga has 10 d electrons which provide very small shielding effect for outer electrons and hence attracts the electrons closer to the nucleus

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19
Q

Discuss ionization enthalpy size trend

A

It decreases down the group as with increase in number of shells, the screening effect increases which makes it more and more easier to remove an electron

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20
Q

Discuss exception wrt ionization enthalpy

A

Ga > Al and Tl > In due to presence of d and f electrons

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21
Q

Discuss electronegativity size trend

A

It decreases from B to Al and then increases marginally

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22
Q

Discuss density size trend

A

Density increases down the group

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23
Q

Discuss physical properties of Boron

A
  1. Boron is non metallic
  2. It is hard and black colored
  3. It has many allotropic forms
  4. It has unusually high MP because of strong crystalline lattice
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24
Q

Discuss physical properties of all other elements

A
  1. They are soft metals
  2. They have low MP
  3. High electrical conductivity
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25
Q

Discuss exception in Gallium’s MP and BP

A

It is extremely low MP to the point where it melts in summer. It also has an incredibly high BP which makes it useful for measuring high temperatures

26
Q

Oxidation State in Boron

A

Because of its small size, the sum of first 2 IEs is high and hence +3 ionic bonds are not formed. Instead, covalent bonds are formed.

27
Q

Oxidation States observed in other elements

A

They show +1 and +3 oxidation states

28
Q

Which OS is more stable and why

A

As we go down the group, due to poor shielding, the increased nuclear charge increases considerably and holds ns electrons tightly. This makes +1 OS more stable as we go down the group

29
Q

Comparison of OS states

A
  1. +1 is predominant in Ga, In, Tl
  2. +3 is very oxidizing
  3. Compounds formed with +1 state are much more ionic than +3 compounds
30
Q

Discuss stability of +3 metals

A

They have only 6 electrons in their outermost orbital making them electron deficient
They accept a pair of electrons, behaving as Lewis acids
Tendency to behave as LA increases with size
Al3+ compounds achieve stability by forming dimers

31
Q

Discuss hydrolysis of +3 compounds

A
  1. Most of them get hydrolyzed to [M(OH)4]- which is tetrahedral and the hybridization of M is sp3
  2. Aluminum gets hydrolyzed to [Al(H2O)6]3+ which is octahedral and the hybridization of Al is sp3d2
32
Q

Discuss reactivity in air

A

Boron is unreactive in crystalline form
Aluminum forms a very thin oxide layer which prevents further attack on the metal
All form oxides and nitrides

33
Q

Oxides formation

A

M + O2 = M2O3

34
Q

Nitrides formation

A

M + N2 = MN

35
Q

Nature of oxides formed

A

Boron trioxide is acidic and reacts with metallic oxides to give metal borates
Aluminum and Gallium oxides are amphoteric
Indium and Thallium oxides are predominantly basic

36
Q

Reactivity of boron with acids/alkalis

A

Boron does not react with either even at moderate temperatures

37
Q

Reactivity of aluminum with acids/alkalis

A

Aluminum reacts with dil. HCl to release H2 gas
However with conc HNO3, it becomes passive due to formation of passive oxide layer
Aluminum also reacts with NaOH to release H2 gas

38
Q

Reactivity with halogens

A

M + X2 = MX3

39
Q

What anomalies can be seen in Boron

A
  1. Unlike other metal trihalides, BX3 is insoluble in water
  2. Other hydrolyzed compounds are also soluble in water except Boron
  3. BF3 (Lewis acid) reacts with NH3 (Lewis base) to complete its octet
  4. Other elements dimerize to attain stability but boron does not as its covalency cannot go beyond 4 due to absence of d orbitals
40
Q

Correct formula of Borax

A

Na2 [B4O5{OH}4] 8H2O

41
Q

Borax + water

A

Borax dissolves in water to give alkaline solution

Borax + water = NaOH + H3BO3 (weak acid)

42
Q

Borax + heat

A

Initially, borax loses water and swells up (Na2B4O7)
On further heating, it forms a transparent liquid which solidifies into a glass like material (B2O3 - boric anhydride/borax bead)

43
Q

Explain the borax bead test

A

Metaborates of many transition elements give different colored borax beads
eg: CoO on heating with a loop of platinum wire gives Co(BO2)2 which is a blue borax bead

44
Q

Structure of Borax

A

White crystalline solid

45
Q

Structure of H3BO3

A

White crystalline solid with soapy touch

Layer structure where planar BO3 units are joined by hydrogen bonds

46
Q

Solubility of H3BO3

A

Sparingly soluble in water but solubility increases with heat

47
Q

How is orthoboric acid prepared

A

By acidifying an aqueous solution of borax

By hydrolysis of any boron compounds

48
Q

Discuss acidity of orthoboric acid

A

Weak monobasic acid

Acts as a Lewis acid by accepting electrons from a hydroxyl ion

49
Q

Heating orthoboric acid

A

H3BO3 + heat = H2BO3 (metaboric acid)

H2BO3 + heat = B2O3

50
Q

How is diborane prepared

A 
BF3 + LiAlH4 = B2H6 + LiF + AlF3
In a laboratory, 
NaBH4 + I2 = NaI + B2H6 + H2
Industrially,
BF3 + NaH = B2H6 + NaF
51
Q

Physical properties of diborane

A

Colorless, highly toxic gas

Catches fire spontaneously in air ( most higher boranes are spontaneously flammable)

52
Q

Hydrolysis of diboranes

A

B2H6 + H2O = B(OH)3 + H2

53
Q

Diborane + Lewis Acid

A

Adducts are formed with the Lewis acid

eg: B2H6 + CO = BH3.CO

54
Q

What is borazine

A

Inorganic benzene

B3N3H6

55
Q

How is borazine formed?

A

B2H6 + NH3 = [BH2(NH3)2]+ [BH4]-

[BH2(NH3)2]+ [BH4]- + heat = B3N3H6 + H2

56
Q

Structure of B2H6

A

Four terminal hydrogens + two boron atoms are all in one plane connected by single bonds
The remaining two hydrogens are bridge atoms above and below this plane with B-H-B bonds

57
Q

Hydridoborates

A

Boron forms a series of hydridoborates, the most important one being [BH4]-
Lithium and sodium tetraborates are formed using this ion

58
Q

What does -ve electrode potential mean

A

High tendency to perform reaction, makes stable product

59
Q

What does +ve electrode potential mean

A

Low tendency to perform, very unstable

60
Q

White fumes appear around the bottle of anhydrous aluminum chloride. Give reason

A

Anhydrous AlCl3 is partially hydrolyzed with atmospheric moisture to liberate HCl gas. Moist HCl appears white in color

61
Q

Why is Boric acid considered weak

A

Because it cannot liberate H+ ions on its own. It receives OH- ions from water, completes its octet and then releases H+ ion

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