P-BLOCK.pdf

chemistry 10th grader helper for cbse students

1. P-BLOCK
-renuha

3. GROUP 15 - picogens
Nitrogen[N](non-metal) , phosphorus[P](non-metal) , arsenic[As] (metalloid) , antimony[Sb](metalloid) ,bismuth(metal)
Nina pina asli sabke bismuth
Electronic config : ns2np3
S is completely filled while p is half filled making them extra stable
Covalent and ionic radii : increases down the group {as the pull of the valence electron towards the nucleus is lesser and
there is more shielding}
N to p the increase in radii is large but As to bismuth the increase is slightly less due to completely filled d and f orbitals.
Ionisation enthalpy [min energy needed to remove valence electron]: decreases down the group {as the pull of electrons
towards the nucleus decreases as size becomes bigger and therefore less force is needed.}
Electronegativity[tendency to gain ] : decreases down the group [it is more ready to give as its electron is loosely bound]
Metallic character : increases down the group
Bp: increases down the group [ph3 has lower bp than nh3 as ph3 doesn’t have hydrogen bonding in liquid state]
NH3 molecules are held together by strong intermolecular hydrogen bonds whereas PH3 molecules are held together by weak van der
Waals bonds. Thus, NH3 has a higher boiling point than PH3.
Mp: increases till arsenic and decreases till bismuth

5. Physical properties
Nitrogen:
Diatomic gas,non metal ,small size , high ionisation enthalpy ,high electroneg , no d orbitals ,can form
pi-pi multiple bonding with itself and others ,doesn’t show allotropy, catenation tendency is weak[The N – N
single bond is highly weak and unstable due to high magnitude of inter-electronic repulsions of
non-bonding electrons which in turn is caused by the single bond’s small bond length. As a result the
catenation tendency becomes weaker due to the mentioned factors leading to instability.],Max oxidation
state is 4[only 4 orbitals are available for bonding] , usual state is 1,2,4
Nitrogen due to small size is able to show pπ-pπ lateral overlap forming N≡N, rest elements due to bigger size
are not able to show pπ-pπ lateral overlap.
All the other elements are solids and show allotropy.
Phosphorus shows +1 and +4
The three important oxidation states of phosphorus are –3, +3 and +5
-3 and +5 decrease down the group while +3 increases down the group [due to inert pair effect]
Nitrogen forms a triple bond and the others form a single bond .
N-n < p-p [due to high repulsion because of small bond length of n]
Nitrogen forms N2, but phosphorus is converted into P4 from P, the reason is pπ – pπ bonding
is weak

6. ●Stability of hydrides decreases from n to b
●Reducing character of the hydrides increase from n to b
●Ammonia mild reducing agent
●Bih3 strongest reducing (Since the stability of hydrides decreases on moving
from NH3 to BiH3, the reducing character of the hydrides increases on moving
from NH3 to BiH3)
●Acidity : tendency to gain e
●Basicity decreases from n to b for hydrides
●For oxides acidity decreases down the grp
●Nitrogen does not form pentahalides as it doesn't have a d orbital , Only forms trihalide
●All the other trihalides are stable except nitrogens
●Pentahalides are more covalent than trihalides[ due larger polarization of bond in
pentahalide state as compared to trihalide state.]
● Among the 15th group elements, as we move from nitrogen to bismuth, the
pentavalency becomes less pronounced and trivalency becomes more
pronounced due to inert pair effect
●All the elements react with metals

7. Dinitrogen or n2: at room temp , it is inert
-commercial prep : liquifaction and fractional distillation of air
Dinitrogen is a gas while all others are solids

9. Ammonia

Preparations:
●Decay of nitrogenous matter / urea
●Decomposition of ammonia salts when treated with caustic soda to give ammonia
●Haber’s process [large scale]:Exothermic reaction

[iron oxide(catalyst {doesn’t get used up}) K2O and Al2O3(promoter)]
Temp:700K
pressure :200 x10^5 Pa
K2O and Al2O3 make sure the equilibrium is attained faster.
combine according to Le Chatelier’s principle.
Produces nitrogenous fertilizers

11. Ammonia properties
●Colourless
●Sp3
●Pungent odour (ammoniacal smell)
●Trigonal pyramidal with nitrogen atom at apex
●Ammonia has 3 bonds pairs and 1 lone pair
●Highly soluble in water [aqueous group is weakly basic due to formation of oh]

●Formation of salts due to presence of acid and the weak base precipitates the hydroxides


●Acts as a lewis base : loses electrons due to presence of lone pairs
●Solid and liquid state they have hydrogen bonds
●Have high melting and boiling points

12. Nitric acid
What catalyst is used for oxidation of ammonia to produce nitric acid?
Platinum-Rhodium gauze
●Preparation :
○From sodium or potassium nitrate



●Ostwald’s process [large scale prep]:
○Catalytic oxidation of nh3 by atmospheric oxygen

13. Properties
●Colourless
●Planar molecule
●In aq sol , behaves as strong acid
●Conc nitric acid is a strong oxidising agent
●Reaction of copper with dil and conc hno3

●Some metals don't dissolve in conc nitric acid due to the formation of a layer on the surface and
prevents further reaction



●Conc nitric acid also oxidises non metals
●Brown ring test: reduces nitrates to nitric oxide , this reacts with fe2+ to form brown colour
○Carried out by adding dilute ferrous sulphate sol to an aq sol containing nitrate ion and slowly adding
conc sulphuric acid
dill Conc
2

14. GROUP 16

15. GROUP 16
-Oxygen family also called as chalcogens
-Contains : oxygen ,sulphur , selenium[Se],Tellurium[Te],Pollium [Po]
OH SAIF SILLY TERI POSE
-Oxygen and sulphur : non metals
-polonium : metal
-Tellurium and selenium: metalloid

16. ●OXYGEN -Most abundant of all the elements on earth , exists as a diatomic molecule , usually in -2 oxi state
-But when with fluorine it exists in +2 → OF2
Oxygen is the most reactive element of group 16.
-Shows limited tendency for catenation
●SULPHUR - always found in combined form as sulphates, exists as S8,(puckered ring structure )has high
tendency for catenation
●TELLURIUM AND SELENIUM are found as sulphates
●POLLIUM Is a radioactive element an is a decay product of thorium and uranium


W

17. Properties
Electronic configuration :ns2np4
Atomic and ionic radii : down the group increases
Oxygen atom is exceptionally small
Mp and bp: down the group increases
Oxygen has very less bp and mp due to small size and exists as a diatom
Ionisation enthalpy : decreases down the group
Group 15 has a higher enthalpy than 16 as 15 is extra stable due to half filled p orbital and fully filled s
Electronegativity : decreases down the group
Oxygen is the most electroneg in the group and 2nd most in the whole table whereas fluorine is 1st in the table
Metallic character : increases down the group
Oxidation states :-2 +2 +4 +6
-2 oxidation state decreases down the group (due to decrease in electroneg down the group)
+4 increases down the group
+6 decreases down the group
Down the group inert pair effect increases therefore causing +4 oxi to increase down and +6 to dec
as we move down the group, the reactivity decreases, i.e., O > S > Se > Te > Po.



The non-participation of the two s electrons in
bonding due to the high energy needed for
unpairing them.
correct order of thermal stability is
H2O>H2S>H2Se>H2Te. decreasing enthalpy for the dissociation
bond down the group. Hence, on heating H-E bond dissociates
easily.

18. Anomalous behaviour of oxygen:
1.small size
2.high electroneg
3.makes nice hydrogen bond
4.a gas due to weak van der waals force
5.diatomic molecule
6.forms double bond between 2 oxygen atoms ,forms pi-pu , the other elements are linked by single bonds
7.absence of d orbitals therefore .limits its covalency to 4



Why is H
2
O a liquid and H
2
S a gas?

H
2
O has oxygen as the central atom. Oxygen has smaller size and higher
electronegativity as compared to sulphur. Therefore, there is extensive hydrogen
bonding in H
2
O, which is absent in H
2
S. Molecules of H
2
S are held together only by weak
van der Waals forces of attraction. Hence, H
2
O exists as a liquid while H
2
S as a gas.

19. Chemical properties
Reaction with hydrogen
-forms hydrides
-acidic character increases down the group of the hydrides as their bond dissociation energy decreases
down. [ can be broken easily , the lower elements]
-Stability down the group of hydrides decreases
-reducing character of hydrides increases down
Reaction with oxygen
-forms oxides
-acidic in nature
-Reducing nature decreases down the group
Down the group oxidizing nature increases

20. Chemical properties
With halogens
-hexahalides [ex4]:
Hexafluorides are the only stable halides
Octahedral structure
Sf6 : hexafluoride
-tetrahalide:
Sf4 is a gas
Sef4 is a liq
Tef4 is a solid
Trigonal bipyramidal
Seesaw geometry
-dihalides :


Group 16 elements have ns2np4 electron
configuration. they would be expected to have a
maximum oxidation state of +6 but the heavy
elements show a lower oxidation state, i.e., +4, due
to inert pair effect due to which s-electrons remain
paired and do not participate in bond formation.
This happens because the s-orbitals held close to the
nucleus, therefore the electrons present in s-orbitals
held strongly by nucleus because of large
electrostatic force.
Since the energy required to unpair these s-electrons
is high, hence the electrons remain paired.
Hence, the stability of +6 oxidation state decreases
and that of +4 oxidation state increases down the
group.

21. dioxygen
Preparation:

22. Oxygen properties
Colourless
Odourless
Oxygen is soluble enough in water to support aquatic life
Three stable isotopes 16o,17o,18o
Reacts with almost all metals and non metals

24. ozone

25. ozone
Pure ozone is a pale blue gas , dark liquid and violet black as solid due to the radiation It is absorbing
Has a characteristic smell
Harmless in low conc and can be explosive in high conc
Thermodynamic unstable with respect to oxygen
Powerful oxidising agent
Used as disinfectant
Ozone layer depletion:
Decrease in the amount of ozone in the atmosphere
Cause:
Use of chlorofluorocarbons
Nitrogen oxides from supersonic jet planes




Due to the ease with which it liberates
atoms of nascent oxygen, ozone acts as a
powerful oxidising agent.

Ozone is thermodynamically unstable
than oxygen and decomposes into
O2. The decomposition is exothermic
and results in the liberation of heat
(ΔH is – ve) and an increase in
entropy (ΔS is positive). This results in
large negative Gibbs energy change
(ΔG). Therefore high concentration of
ozone can be dangerously explosive.

26. sulphur ‘s allotropic forms
1.Alpha-sulphur or rhombic sulphur
-more stable at room temp
-but at 369K it gets converted to beta sulphur or monoclinic sulphur and that temp is called transition temp

27. GROUP 18

28. Group 18
-All of them are gases
-Chemically unreactive due to complete valence shell configuration.
-Noble gases
-Form very few compounds
-Helium[He] , neon[Ne] , argon[Ar] , krypton[Kr] , xenon[Xe] , radon[Rn]
Hey neena , arey karaya xerox ready
-Main commercial source is natural gas
-Occurs in atmosphere except radon , argon is the most abundant in atmosphere
Radon is the most soluble noble gas in water due to dipole induced dipole interactions
Helium can diffuse through rubber
Decay products of radium are radon and helium

29. properties
Electronic config: ns2np6 valence is 8

Outermost shell is fully filled

Have extra filled config
Exception: helium 2 valence electrons

Atomic radius : increases down the group

Bp and mp : have low mp cause they are monatomic [like he,ne etc](have weak dispersion forces)
Helium has the lowest bp of all elements

Very high ionisation enthalpy due to stable configuration.
Ionisation enthalpy down the group decreases due to increase in size

Electron gain enthalpy will be very high as they have stable config and no tendency to accept and is
in positive values

Metallic character[tendancy to donate ]: increases down the group[pull towards nucleus is less so
like easy to donate]

30. Physical properties
-colourless
-tasteless
-odourless
Sparingly soluble in water
Helium is the second most abundant gas in the universe
Xenon can react with highly electroneg elements like f and o

31. Xenon compounds
Xenon forms 3 fluorides : xef2 , xef4,xef6





Colourless crystalline solids
Sublime at 298 K
Powerful fluorinating agent
Readily hydrolysed even by traces of water

32. Xenon compounds
Xef2:

33. Xef4

34. Xef6;







Xeof4: square pyramidal
Xeo2f2: pyramidal

35. Xenon-oxygen compounds
2
Xe03 id highly explosive and a powerful oxidising agent.
Colour of XeO3 Colourless
Xeo3 is a solid

36. uses





Helium is non inflammable / incombustible and a light gas
Helium has the smallest size and fulfilled orbitals hence maximum ionization energy.
)Helium: meteorological observations:: Argon: metallurgical processes

37. GROUP 17

38. halogens
Halo: salt , gene:producer Therefore halogens are salt producers
-highly reactive
-non metals
At: 85 ,, Uus :117
Fir class boring? Inquired astha
Fluorine is fairly abundant ,present mainly as insouble fluorides
Cl, i , br are found in sea water
Asteline : radioactive element



At
Chlorine water on standing loses its colour and
forms:-
(1) HCl and HClO2
(2) HCl only
(3) HOCl and HOCl2
(4) HCl and HOCl
Hence option (4) is the answer.

39. trends
1.config : ns2np5
2.very hungry for electrons as it needs only one more to become stable ,thereore very reactive
3.atomic radii : increases down the group
Fluorine is exceptionally small
4.increases down the group
Halogens are soluble in water which follows the order
F
2
> C1
2
> Br
2
> I
2

5.mp and bp : incrrases down the group as the atomic size becomes bigger and the vander waals force increase
6.ionisation enthalpy : decreases down the group , very high IE as they are almost near stable ocngif
7. Electroneg : very electroneg , decreases down the group as the nucleus is very far from the valence shell and therefore it’s power isnt
enough to pull , fluorine is the most electroneg in the group and hte entire tbale
8.electron gain enthalpy : energy req to add an electron to an atom and energy is released : the change in enthalpy is negative : : very large
negative value , down the group it decreases as the tendancy to pull becomes less as the nucleus doesnt have that much power to pull no
due to many shells .
Exceptions : floruine’s gain enthalpy is lesser than chlorine as fluorine is tooo small and theres a lot of replusion between the electrons
inside.

40. All halogens are coloured
like: Fluorine: Dull yellow in color. Chlorine: Greenish yellow. Bromine: Reddish brown. Iodine:
Violet
Oxidation state : usually -1 ,but when it reacts with elements with higher electro neg then it becomes plus
Other oxi states are : +3 , +5 , +7
Very good oziding agents , oxiding power reduces down the group
Fluorine is the best oxidising agent
Only oxidises halies with higher atomic number

41. Anamalous properties of flourine
Small size
High electro negativity
Non availability of d orbitals in valence shell
Low f-f bond dissociation enthalpy , breaks easily
Highly reactive , exothermic usually
All halogens react with metals and non metals to form halides
Reactivity of halogens decreases down the group

42. Halogens with hydrogen and water
Affinity for hydrogen decreases downt eh group
Stability of hydrogen halides decreases down the group
HF > HCl > HBr > HI
Due to increase in size, bond length increase due to which bond dissociation energy decrease therefore stability decrease
○All act as Lewis acids as they accept electron.





Halogen with water

43. Reaction of iodine with water is non spontaneous therefore reactivity with water decreases down the group
Reaction with oxygen :: these are called oxygen flourides
Fluorine forms two oxides, OF
2
and O
2
F
2

-flourine with oxygen forms of2 which is thermally stable at 298 k




Clo2 is a good bleaching agent
Bromines are least stable oxides due to middle row anomaly , the bond between bromine and oxygen is easily
breakable
The iodine oxides, i:e., I
2
O
4
, I
2
O
5
,I
2
O
7
are insoluble solids and decompose on heating. I
2
O
5
is a very good oxidising agent
and is used in the estimation of carbon monoxide.
Bromines are Highly reactive oxidising agents

44. Reaction with metal
Forms metal halide
Down the group , the ionic character decreases

45. Reaction wiht halogens
Formation of interhalogen compounds
Type 1.


2.

46. Summary of interhalogens






Higher the ratio of x and x’ , more is the number of atoms per molecule increases

47. Interhalogen prep

48. Inter halo prop
Cobalent molecules
Diamagnetic \
Solids or liquids
Exception is CIF is a gas
Very useful flourinating agent
Used as a non aqueous sol

49. chlorine

50. Chlorine prep
1.Already mentioned [heating manganese dioxide with concentrate hcl]
2.Mno2 +4nacl+4h2so4 → mncl2+4nahso4 +2h2o +cl2
3.

51. Chlorine prop
Greenish yellow gas
Pungent odour
Can be liquified easily
Soluble in water
Reacts with non metals and metals to form chlorides →

52. Reaction of chlorine with alkali
Alkali can be cold and dilute alkali :



Nacl : sodium chloride
Naocl : sodium hypochlorite

53. Hocl : hypochlorus acid , very unstable , forms nascent oxygen [O] → very powerful bleaching agent
Hence bleaching action is due to oxidation

55. Hydrogen chloride
Aq form of hydrogen chloride is called hcl
Prepared by glauber in 1648 by heating common salt with conc h2so4

56. colour less
Pungent odour
Easily liquified
Freezes to a white crystalline solid
Extremely soluble in wate
Aqua regia :
Mixture of 3 parts of conc hcl and 1 part of conc hno3
Used for dissolving noble metals ,gold , platinum as they dont react easily with elements but aqua regia does
Real life uses of aqua regia : putting blackned gold in aqua regia , removes the top bad layer and becomes
clean but as we dissolve it everytime , a small amount of gold is lost

58. Oxcaacids