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Chemistry > P Block Elements > Flashcards

P Block Elements Flashcards

appreciate the general trends in chemistry of p-block elements ; describe the trends in physical & chemical properties of group 13 & 14 elements ; explain anomalous behaviour of B & C ; describe allotropic forms of C ; know chemistry of done important compounds of B, C & Si ; list the important uses of group 13 & 14 elements & their compounds

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1
Q

Reason for variation in properties of heavier p-block elements

A

Influence of d & f elements in inner core

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2
Q

Boron is metallic or nonmetallic?

A

Non metallic

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3
Q

Colour of boron

A

Black

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4
Q

Texture of boron

A

Extremely hard & refractory solid

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5
Q

How does boron exist

A

In many allotropic forms

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6
Q

Melting point of boron

A

Unusually high

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7
Q

Reason of melting point of boron

A

Due to very strong crystalline lattice

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8
Q

Texture of group 13 elements

A

Except boron all are soft metals

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9
Q

Electrical conductivity of group 13 elements

A

Except boron high electrical conductivity

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10
Q

Melting point of group 13 elements

A

Except boron low melting point

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11
Q

Melting point and state of gallium

A

Unusually low melting point (303K)

Exist in liquid state during summer

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12
Q

Boiling point of gallium

A

High boiling point (2676 K)

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13
Q

Use of boiling point of gallium

A

Measuring high temperatures

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14
Q

Trend of density of group 13 elements

A

Density of elements increases down the group from boron to thallium

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15
Q

What type of compounds do boron form & why?

A

Covalent

Due to small size of boron the sum of its first ionization enthalpy is very high. This prevents it to form +3 ions and forces it to form only covalent compounds

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16
Q

Aluminium is electropositive or negative

A

Electropositive

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17
Q

How can Al 3+ ions be formed when it is not possible in case of boron

A

As we move from boron to aluminium the sum of first three ionisation enthalpies of aluminium considerably decreases & is thus able to form Al 3+ ions

18
Q

What is responsible for inert pair effect in group 13 elements

A

down the group due to poor shielding effect of intervening d and f orbitals the increased effective nuclear charge holdes ns electrons tightly

19
Q

Result of inert pair effect in group 13 elements

A

ns electrons are restricted for participation in bonding

This only p orbital electrons are involved in bonding

20
Q

Which oxidation States can be observed in gallium indium and thallium

A

+1 & +3

21
Q

Which oxidation states are stable for group 13 elements

A

The relative stability of +1 oxidation state progressively increases for heavier elements as :

Al < Ga < In < Th

In thallium +1 oxidation state is predominant whereas the +3 oxidation State is highly oxidising in character

22
Q

Which oxidation states are stable for group 13 elements

A

The relative stability of +1 oxidation state progressively increases for heavier elements as :

Al < Ga < In < Th

In thallium +1 oxidation state is predominant whereas the +3 oxidation State is highly oxidising in character

23
Q

What can be expected from energy considerations from the compounds of group 13 elements

A

Compounds in +1 oxidation state are more ionic than those in +3 oxidation state

24
Q

Electrical conductivity of boron

A

Low

25
Q

Colour of aluminium

A

Bright silvery white metal

26
Q

Tensile strength of aluminium

A

High

27
Q

Electrical and thermal conductivities of aluminium

A

High

28
Q

Electrical conductivity of aluminium as compared to copper

A

On way to weight basis, conductivity of aluminium is twice that of copper

29
Q

Which which elements do aluminium form alloys

A

Cu, Mn, Mg, Si & Zn

30
Q

Use of aluminium and its compounds for domestic purposes

A

Now reduced considerably because of their toxic nature

31
Q

Uses of aluminium and its alloys

A

By giving various shapes, used in packing, utensil making, construction, aeroplane & transportation industry

32
Q

How are boron fibres used

A

In making bullet proof vest and light composite material for aircraft

33
Q

Where are metal brides used and why and how

A

The boron 10 isotope has high ability to absorb neutrons

Thus metal borides are used in nuclear industry as protective shields and control rods

34
Q

Main application of borax and boric acid

A

Manufacturer of heat resistant glasses like Pyrex, glass wool & fiberglass

35
Q

Other uses of borax

A

As a flux for soldering metals, for heat, scratch and stain resistant glazed coating to earthenwares, as constituent of medicinal soaps

36
Q

How is boron used in medicine

A

An aqueous solution of orthoboric acid is generally used as a mild antiseptic

37
Q

What type of structure does graphite have

A

Layered

38
Q

Force between different layers of graphite

A

Van der Waals force

39
Q

Distance between two graphite layers

A

340 pm

40
Q

Graphite layers are composed of?

A

Planar hexagonal rings of carbon atoms

41
Q

C-c bond length graphite layer

A

141.5 pm

42
Q

Hybridization of each carbon atom in graphite layer

A

sp2

Chemistry (1 decks)

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