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
Reason for variation in properties of heavier p-block elements
Influence of d & f elements in inner core
Boron is metallic or nonmetallic?
Non metallic
Colour of boron
Black
Texture of boron
Extremely hard & refractory solid
How does boron exist
In many allotropic forms
Melting point of boron
Unusually high
Reason of melting point of boron
Due to very strong crystalline lattice
Texture of group 13 elements
Except boron all are soft metals
Electrical conductivity of group 13 elements
Except boron high electrical conductivity
Melting point of group 13 elements
Except boron low melting point
Melting point and state of gallium
Unusually low melting point (303K)
Exist in liquid state during summer
Boiling point of gallium
High boiling point (2676 K)
Use of boiling point of gallium
Measuring high temperatures
Trend of density of group 13 elements
Density of elements increases down the group from boron to thallium
What type of compounds do boron form & why?
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
Aluminium is electropositive or negative
Electropositive
How can Al 3+ ions be formed when it is not possible in case of boron
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
What is responsible for inert pair effect in group 13 elements
down the group due to poor shielding effect of intervening d and f orbitals the increased effective nuclear charge holdes ns electrons tightly
Result of inert pair effect in group 13 elements
ns electrons are restricted for participation in bonding
This only p orbital electrons are involved in bonding
Which oxidation States can be observed in gallium indium and thallium
+1 & +3
Which oxidation states are stable for group 13 elements
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
Which oxidation states are stable for group 13 elements
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
What can be expected from energy considerations from the compounds of group 13 elements
Compounds in +1 oxidation state are more ionic than those in +3 oxidation state
Electrical conductivity of boron
Low
Colour of aluminium
Bright silvery white metal
Tensile strength of aluminium
High
Electrical and thermal conductivities of aluminium
High
Electrical conductivity of aluminium as compared to copper
On way to weight basis, conductivity of aluminium is twice that of copper
Which which elements do aluminium form alloys
Cu, Mn, Mg, Si & Zn
Use of aluminium and its compounds for domestic purposes
Now reduced considerably because of their toxic nature
Uses of aluminium and its alloys
By giving various shapes, used in packing, utensil making, construction, aeroplane & transportation industry
How are boron fibres used
In making bullet proof vest and light composite material for aircraft
Where are metal brides used and why and how
The boron 10 isotope has high ability to absorb neutrons
Thus metal borides are used in nuclear industry as protective shields and control rods
Main application of borax and boric acid
Manufacturer of heat resistant glasses like Pyrex, glass wool & fiberglass
Other uses of borax
As a flux for soldering metals, for heat, scratch and stain resistant glazed coating to earthenwares, as constituent of medicinal soaps
How is boron used in medicine
An aqueous solution of orthoboric acid is generally used as a mild antiseptic
What type of structure does graphite have
Layered
Force between different layers of graphite
Van der Waals force
Distance between two graphite layers
340 pm
Graphite layers are composed of?
Planar hexagonal rings of carbon atoms
C-c bond length graphite layer
141.5 pm
Hybridization of each carbon atom in graphite layer
sp2
