1
THE p-BLOCK ELEMENTS
GROUP 13 ELEMENTS: (ns² np¹)
Indroduction :
● Only boron forms [BF4]-¹ ion, while aluminium can form [AlF6]-³ ion due to availability of
empty 3d orbital.
● First members of all p-BLOCK elements forms pπ - pπ bond due to influences of
combined effect of size and unavailability of d - orbital , while heavier elements can
form dπ - dπ (or) dπ - pπ bonds .
● The co-ordination number of the heavier species elements also higher than for the first
elements due to the contribution of the d- orbital for the π bond .
● Boror family contains
a. Boron 5
b. Aluminium 13
c. Galium 31
d. Indium 49
e. Thallium 81
f. Nihonium 113
■ (mass no: 286 gmol-¹,
■ half life - 20second)
, P- block elements 2
● Abundance
Elements Percentage of abundance Rank
Oxygen 45.5% I
Silicon 27.7% II
Aluminium 8.3% III
Atomic radii:
● Atomic radii increases down the group.
● Exception: Atomic radii of gallium (135pm) is lesser than aluminium (143 pm ) due to poor
shielding effect of 3d orbital.
Ionization enthalpy :
● Decreases down the group
● Some discontinuity in the ionisation enthalpy values between Al and Ga and between In
and Tl are due to inability of d and f- orbital which has poor screening effect to
compensate the increase in the nuclear charge .
B > Tl > Ga > Al > In
Electronegativity:
● Down the group, electronegativity first decreases fron B to Al and then increases
marginally
B > Al ≤ Ga ≤ In ≤ Tl
Physical properties:
● Boron is non metallic , hard and black coloured solid and has high melting point due to
very strong crystalline lattice .
, P- block elements 3
● Other members are soft metal with low melting point and high electrical electrical
conductivity .
● Gallium with low melting point (303K ) can exist in liquid during summer and it's high
boiling point (2676K) makes it useful for measuring high temperature
● Density of elements increase down the group from boron to thallium.
Chemical properties :
● +1 oxidation as expected from the energy considerationa were more ionic than those in
+3 oxidation .
● BCl3. NH3 can be easily formed because of the electron deficienct (Lewis acid)
tendency of boron.
● AlCl3 achieves stability by forming a dimer.
●
● Trivalent state of the most of the compounds being covalent are hydrolysed in water
● Hydrolysis of trichlorides in water form tetrahedral with sp³ hybridization [M(OH)4]-.
● Hydrolysis of Aluminium trichlorides in acidified aqueous solution form octahedral
[Al(OH)6]+³ ion. (Due to 3d orbital)
Reactivity towards air :
● Crystalline boron is unreactive .
, P- block elements 4
● Amorphous boron and aluminium metal on heating the air form their respective oxide and
at high temperature form their respective nitrides .
● Aluminium forms a thin oxide layer on the surface which protects the metal from
further attack..
Oxides Nature of oxide
B2O3 Acidic
AL2O3 Amphoteric
Ga2O3 Amphoteric
In2O3 Basic
Tl2O3 Basic
● Boron trioxide reacts with basic mettalic oxide like alkali metal oxide . But Boron does
not react with acid or alkali.
Reactivity towards acids and base :
● Aluminium dissolves in dilute HCl and liberates dihydrogen.
2Al(s) + 6HCl(aq) —» 2Al+³(aq) + 6Cl-¹(aq) + 3H2 (g)
● Concentrated nitric acid is rendered passive by forming a protective oxide layer on the
surface.
● Aluminium reacts with aqueous alkali and liberate dihydrogen.
2Al(s) + 2NaOH (aq) + 6H20 (l) —» 2Na +[Al(OH)4]- (aq) + 3 H2 (g)
Reactivity towards halogens :
● These elements react with halogens to form trihalide except TlI3
, P- block elements 5
● White fume appear around the bottle of anhydrous aluminium chloride due to the partial
hydrolysis of anhydrous aluminium chloride with the atmospheric moisture to liberate
HCl gas . Moist HCl appears white in colour .
Important trend and Anomalous properties of Boron :
● Trichlorides, tribromides , Tri-iodides of All Elements are covalent in nature and are
easily hydrolysed in water .
● Species like octahedral [M(OH)6]+³ and Tetrahedral [M(OH)4]-, exist in aqueous medium
except in boron .
Group 14 Elements : The Carbon Family (ns²np²)
Indroduction :
● Carbon is the seventeenth most abundant element by mass and most versatile element in
the world .
● C¹⁴ has half life period of 5770 years.
● Tin occurs mainly as cassiterite .
● SnO2 and lead is obtained as Galena.
● Ultrapure form of germanium and silicon are used to make transistor and semiconductor.
● The carbon family including:
a. Carbon 6
b. Silicon 14
c. Germanium 32
d. Tin 50
THE p-BLOCK ELEMENTS
GROUP 13 ELEMENTS: (ns² np¹)
Indroduction :
● Only boron forms [BF4]-¹ ion, while aluminium can form [AlF6]-³ ion due to availability of
empty 3d orbital.
● First members of all p-BLOCK elements forms pπ - pπ bond due to influences of
combined effect of size and unavailability of d - orbital , while heavier elements can
form dπ - dπ (or) dπ - pπ bonds .
● The co-ordination number of the heavier species elements also higher than for the first
elements due to the contribution of the d- orbital for the π bond .
● Boror family contains
a. Boron 5
b. Aluminium 13
c. Galium 31
d. Indium 49
e. Thallium 81
f. Nihonium 113
■ (mass no: 286 gmol-¹,
■ half life - 20second)
, P- block elements 2
● Abundance
Elements Percentage of abundance Rank
Oxygen 45.5% I
Silicon 27.7% II
Aluminium 8.3% III
Atomic radii:
● Atomic radii increases down the group.
● Exception: Atomic radii of gallium (135pm) is lesser than aluminium (143 pm ) due to poor
shielding effect of 3d orbital.
Ionization enthalpy :
● Decreases down the group
● Some discontinuity in the ionisation enthalpy values between Al and Ga and between In
and Tl are due to inability of d and f- orbital which has poor screening effect to
compensate the increase in the nuclear charge .
B > Tl > Ga > Al > In
Electronegativity:
● Down the group, electronegativity first decreases fron B to Al and then increases
marginally
B > Al ≤ Ga ≤ In ≤ Tl
Physical properties:
● Boron is non metallic , hard and black coloured solid and has high melting point due to
very strong crystalline lattice .
, P- block elements 3
● Other members are soft metal with low melting point and high electrical electrical
conductivity .
● Gallium with low melting point (303K ) can exist in liquid during summer and it's high
boiling point (2676K) makes it useful for measuring high temperature
● Density of elements increase down the group from boron to thallium.
Chemical properties :
● +1 oxidation as expected from the energy considerationa were more ionic than those in
+3 oxidation .
● BCl3. NH3 can be easily formed because of the electron deficienct (Lewis acid)
tendency of boron.
● AlCl3 achieves stability by forming a dimer.
●
● Trivalent state of the most of the compounds being covalent are hydrolysed in water
● Hydrolysis of trichlorides in water form tetrahedral with sp³ hybridization [M(OH)4]-.
● Hydrolysis of Aluminium trichlorides in acidified aqueous solution form octahedral
[Al(OH)6]+³ ion. (Due to 3d orbital)
Reactivity towards air :
● Crystalline boron is unreactive .
, P- block elements 4
● Amorphous boron and aluminium metal on heating the air form their respective oxide and
at high temperature form their respective nitrides .
● Aluminium forms a thin oxide layer on the surface which protects the metal from
further attack..
Oxides Nature of oxide
B2O3 Acidic
AL2O3 Amphoteric
Ga2O3 Amphoteric
In2O3 Basic
Tl2O3 Basic
● Boron trioxide reacts with basic mettalic oxide like alkali metal oxide . But Boron does
not react with acid or alkali.
Reactivity towards acids and base :
● Aluminium dissolves in dilute HCl and liberates dihydrogen.
2Al(s) + 6HCl(aq) —» 2Al+³(aq) + 6Cl-¹(aq) + 3H2 (g)
● Concentrated nitric acid is rendered passive by forming a protective oxide layer on the
surface.
● Aluminium reacts with aqueous alkali and liberate dihydrogen.
2Al(s) + 2NaOH (aq) + 6H20 (l) —» 2Na +[Al(OH)4]- (aq) + 3 H2 (g)
Reactivity towards halogens :
● These elements react with halogens to form trihalide except TlI3
, P- block elements 5
● White fume appear around the bottle of anhydrous aluminium chloride due to the partial
hydrolysis of anhydrous aluminium chloride with the atmospheric moisture to liberate
HCl gas . Moist HCl appears white in colour .
Important trend and Anomalous properties of Boron :
● Trichlorides, tribromides , Tri-iodides of All Elements are covalent in nature and are
easily hydrolysed in water .
● Species like octahedral [M(OH)6]+³ and Tetrahedral [M(OH)4]-, exist in aqueous medium
except in boron .
Group 14 Elements : The Carbon Family (ns²np²)
Indroduction :
● Carbon is the seventeenth most abundant element by mass and most versatile element in
the world .
● C¹⁴ has half life period of 5770 years.
● Tin occurs mainly as cassiterite .
● SnO2 and lead is obtained as Galena.
● Ultrapure form of germanium and silicon are used to make transistor and semiconductor.
● The carbon family including:
a. Carbon 6
b. Silicon 14
c. Germanium 32
d. Tin 50
