UNIT- 7 P – BLOCK ELEMENTS

Properties at Glance

Properties Group. 15 Group. 16 Group. 17 Group. 18Elements N, P, As, Sb, Bi

(P nicogens)O, S, Se, Te, Po

(Chalogens)F, Cl, Br, I, At

(Halogens)He, Ne, Ar,

Kr, XeElectronic

configurationns2, np3 ns2, np4 ns2, np5 ns2, np6

Occurance Atmosphere has 78% N2 in earth

crust is present as NaNO3, KNO3, it is also in proteins

in plants and animals.

P – Ca9(PO4)6.CX2

(X = F2Cl2, OH)

eg(fluorapatite Ca9(PO4)6.CaF2)

It is present in bones and living

cells, Phosphoprotien is in milk and eggs.

As,Sb, Bi are found in Sulphide

minerals.

O – atmosphere - 21%

Earth crust – 46.6%S – exists as

sulphatesEg. CaSO4.2H2O,

MgSO4.7H2O, organic minerals like eggs, proteins, garlic,

hair, wool, contain sulphur.

Se, Te are found as metal selenides and

tellurides in sulphide ores.

Po – obtained by decay of Th and U

minerals.

F – as CaF2, Na3AlF6, 3Ca(PO4)2.CaF2

Small quantities are present in soil, river –

H2O, plants, bones and teeth.

Sea – H2O has Cl-, Br-, I- of Na+, K+,

Mg2+, Ca2+.

Certain marine life contain I2, various sea

weeds and chile saltpetre has has I2.

Sea weed – 5% I2Chile saltpeter - 0.2%

NaOI3

(iodate)

Ar – 1%He, Ne found in radioactive

minerals, pitchblende, monazite, cleveite.

He – main source

natural gas

Group-15N-70,P-110,

As,121 ,Sb-141 , Bi-148

As - Bi - a small increase is seen due to presence of completely

filled d/f orbitals.

It is much higher than gp.14. I.E increases down the gp due to

half-filled stable configurations.

It decreases down the group because metallic character decreases down

the group.

Less metallic than gp.14 and

metallic character increases down

the group.N, P - non-metals

As, Sb - metalloidsBi - metal.

N, Bi - no allotropes

P - red, white, black

As, Sb - yellow, gray

Group-16O-66, S-104, Se-117,

Te-137, Po-230

I.E1 < I.E2 of gp 15.

O has highest EN, (next to F).

gp.16 elements have high negative gain

enthalpy because of its small size.

S, O - non-metalSe, Te - metalloids

Po - metallic

O - O2, O3

Se - 8 allotropic forms, grey.Se conducts electricity

Te - 1 formPo - 2 forms.

Group-17F-64, Cl-99, Br-114,

I-133

I.E are very high. They have little

tendency to loose electrons.

X have maximum electron gain

enthalpy because they need only one

electron to complete the noble gas configuration.

X have very high ENF - most electro

negative compound.

All are non metals. Only I shows metallic

lusture.

Group-18He-120, Ne-160, Ar-190,Kr-200,Xe-220

Highest I.E in their respective period due to stable electronic configuration Electron gain enthalpy is positive because of noble gas configuration.

All are non-metals.

PropertiesAtomic radius

(Covalent radius in pm)

Ionization enthalpy

Electro negativity

(EN)

& electron gain enthalpy

Metallic character

Allotropy

Properties

Oxidation state

Hydrides

Oxides

Group-15

N(-3) Mg3N2

-2 NH2NH2

-1 NH2OHP(-3) Ca3P2

(-2) P2H4

all elements show +3 to +5

oxidation state.Down the gp +5

state stability decreases.

(Inert pair effect)

MH3

1. Stability decreases down

the gp.2. reducing character

decreases down the gp.

3. Basicity decreases down

th gp.

E2O3, E2O5

(more acidic)N2O3, P2O3 - acids

As, Sb oxides - amphoteric

Bi oxide - basic.

Group-15

Group-16

O - -2, -1, +2S, Se, Te, Po - +4,

+6, +2.

H2E (E- O, S, Se, Te)1. Acidic character

increases from H2O - H2Te

2. Stability decreases from H2O - H2Te.

3. except H2O all are good reducing agent,

H2Te - best.

EO2, EO3

SO2, O3 - gasesSeO2 - solid

Reducing property decreases from

SO3 - TeO2

(Oxidising agent)EO3 - SeO3, TeO3.

Group-17

F - 0nly -1Other X - -1, +1, +3,

+5, +7some X show +4 and

+6.

HXAcidic strength

HF < HCl < HBr < HI

Dissociation enthalpyHF > HCl > HBr >

HI

OF2, O2F2

Stable at 298KCl, Br, I form oxides

i range +1 to +7Stability of oxides-

I > Cl > BrCl2O, ClO2, Cl2O6,

Cl2O7 -highly reactive

oxidising agent and tend to explode.ClO2 - bleaching

agent

Br2O, BrO2, BrO3.

Group-18

----

----

XeO3

Properties

Halides

Reactivity towards metals

EX3, EX5

NX3 cannot be formed because of absence of d - orbital in case of N, Only NF3 is stable. All EX3

are covalent, except BiF3.

CaN2, Ca3P2

Na3As2, Zn3Sb2

o.s.(-3)

Group-16

EX6, EX4, EX2

(gases)SF6 - highly stableSF4(g), SeF4(lq),

TeF4(s)All elements except Se form dichlorides/

dibromides. Monohalides are

dimeric(S2F2, S2Cl2, S2Br2)

2Se2Cl2 - SeCl4 + 3Se(disproportionation

reaction)

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Group-17

XX2, XX3, XX5, XX7 - Inter halogen compounds

highly reactive.

Ionic characterMF > MCl > MBr >

MIIf M exhibits more oxidation, higher oxidation state

halides are covalent.

Group-18

XeF2, XeF4, XeF6, XeOF4,

XeO2F2

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Equations at a glance

(1) (NH4)2Cr2O7 → N2 + 4H2O + Cr2O3 (2) Ba(N3)2 → Ba + 3N2

(3) NH2CONH2 + 2H2O → (NH4)2CO3↔2NH3+H2O+CO2

(4) 2NH4Cl + Ca(OH)2 → 2NH3 + 2H2O + CaCl2(5) (NH4)2SO4 + 2NaOH → 2NH3 + 2H2O + Na2SO4

(6) 2FeCl3 + 3NH4OH → Fe2O3.XH2O + 3NH4Cl (7) ZnSO4 + 2NH4OH →Zn(OH)2 + (NH4)2SO4

(8) 4H3PO3 → 3H3PO4 + PH3

(9) 4AgNO3 + 2H2O + H3PO2 → 4Ag + 4HNO3 + H3PO4

(10) 2Se2Cl2 → SeCl4 + 3Se (11) 2Ag2O → 4Ag + O2

(12) 2HgO → 2Hg + O2

(13) 2H2O2 → 2H2O + O2

(14) 2ZnS + 3O2 → 2ZnO + 2SO2

(15) Al2O3 + 6HCl +9H2O → 2[Al(H2O)6]3+ + 6Cl¯ (16) Al2O3 + 6NaOH + 3H2O → 2Na3[Al(OH)6] (17) 2I¯ + H2O + O3 → 2OH¯ + I2 +O2

(18) NO +O3 → NO2 + O2

(19) 4FeS2 + 11O2 → 2Fe2O3 + 8SO2

(20) 2NaOH +SO2 → Na2SO3 + H2O (21) Na2SO3 + H2O + SO2 → 2NaHSO3

(22) SO2 + Cl2 → SO2Cl2 (23) 2Fe2+ +SO2 +2H2O → 2Fe + SO4 +4H (24) 5SO2 + 2MnO4-- + 2H2O → 5SO42- + 4H+ + 2Mn2+

(25) F2 + 2X¯ →2F¯ + X2 (X=Cl,Br,I) (26) 2F2 +2H2O→ 4H+ + 4F- +O2

(27) X2 + H2O → HX + HOX (28) 4I- + 4H+ + O2 → 2I2 + 2H2O (29) 4NaCl + MnO2 + 4H2SO4 → MnCl2 + 4NaHSO4 + 2H2O + Cl2 (30) 2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 8H2O + 5Cl2 (31) 4HCl + O2 → 2Cl2 + 2H2O (DEACON’S PROCESS) (32) 2Al + 3Cl2 → 2AlCl3

(33) C10H16 + 8Cl2 → 16HCl + 10C (34) 8NH3 +3Cl2 → 6NH4Cl +N2

(35) NH3 + 3Cl2 → NCl3 + 3HCl (36) 2NaOH + Cl2 → NaCl + NaOCl +H2O (37) 6NaOH + 3Cl2 → 5NaCl + NaClO3 + 3H2O (38) 2Ca(OH)2 + 2Cl2 → Ca(OCl)2 + CaCl2 + 2H2O (39) 2FeSO4 + H2SO4 + Cl2→ Fe2(SO4)3 + 2HCl (40) Na2SO3 + Cl2 + H2O → Na2SO4 + 2HCl (41) SO2 + 2H2O + Cl2 → H2SO4 + 2HCl

(42) I2 + 6H2O + 5Cl2 → 2HIO3 + 10HCl (43) Cl2 + H2O → 2HCl +O (44) Cl2 + F2 → 2ClF (45) I2 + Cl2 → 2ICl (46) XX’ + H2O → HX’+HOX (47) Xe + F2 → XeF2

(48) XeF4 + O2F2 → XeF6 + O2 (49) 2XeF2 + 2H2O → 2Xe + 4 HF +O2

(50) XeF2 + PF5 → [XeF]+ [PF6]¯ (51) XeF4 + SbF5 → [XeF3]+ [SbF6]¯ (52) XeF6 + MF+ → M [XeF7]¯ (M-Na, K,Rb or Cs) (53) 6XeF4 + 12H2O → 4Xe + 2XeO3 + 24HF + 3O2

(54) XeF6 + 3H2O → XeO3 + 6HF (55) Xe F6 +H2O → XeOF4 + 2HF (56) XeF6 + 2H2O → XeO2F4 + 4HF

Structures Of Compounds

1) NH3

2) White Phosphorus

3) Red Phosphorus

4) PCl3

5) PCl5

6)O3

7) S6

8) S8

9) SO2

10) HOClO

11) HOCl

12) HOClO2

13) HOClO3

14) BrF3

15) XeF2

16) XeF4

17) XeFO4

18) XeF6

19) XeO3

20) H4P2O7

21) H3PO3

22) H3PO2

23) H2SO3

24) H2SO4

25) H2S2O8

26) H2S2O7

27) N2O

28) NO

29) N2O4

30) NO2

31)N2O5

32) ICl4

33) IBr2 - 34)

BrO-3

Some important gases

S.no Gas Laboratory Preparation Properties Uses

1. N2 NH4Cl + NaNO2 → N2 + 2H2O+ NaCl Colourless, odourless, tasteless, non – toxic ,inert gas ∆6Li + N2→2Li3N

In manufacture of NH3, to provide inert atmosphere in industries.

2. O2 ∆2KClO3 →2KCl + 3O2 MnO2

Colourless, odourless, low solubility in water reacts with almost all metal & non-metal.

Used in respiration & combustion oxygen cylinders are used in hospitals.

3. O3 Electric discharge 3O2→2O3

Pale blue lq., dark blue lq., violet solid, strong oxidizing- agentNO + O3→ NO2 + O2

As germicide, disinfectant & for sterilizing H2O.

4. SO2 S + O2→SO2

2- SO3 +2H+→H2O + SO2

4FeS2 + 11O2→2Fe2O3 + 8SO2

Colourless , pungent smelling gas, highly soluble in H2O

in refining sugar in bleaching wool

5. Cl2 MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O Greenish yellow gas, suffocating odour reacts with metal & non-metal to form chlorides

For bleaching wood pulp in manufacture of dyes

SOME IMPORTANT ACIDS

Prep.:- Ostwald process

NaNO3 + H2SO4 → NaHSO4 + HNO3

Pt/Rh4NH3 + 5O2 → 4NO + 6H2O condition : 500 K/9 bar

2NO2 + O2↔2NO2

3NO2 + H2O → 2HNO3 +NO

3Cu + 8HNO3(dil.) → 3Cu(NO3)2 + 2NO + 4H2O

Cu + 4HNO3(conc.) → Cu(NO3)2 + 2NO2 + 2H2O

I2 + 10HNO3 → 2HIO3 + 10NO2 + 4H2O

USE:- (HNO3) In manufacture of NH4NO3 for fertilizer, etching of metals.

H2SO4

Contact process

S + O2 → SO2

V2O5

SO2+ O2 → SO3

SO3 + H2SO4 →H2S2O7

H2S2O7 + H2O → 2H2SO4

Colourless dense lq, low volatility, strong affinity for H2O, strong oxidizing agent.Cu + 2H2SO4(conc.) → CuSO4 + SO2 + 2H2O

C + 2H2SO4 → CO2 + 2SO2 + 2H2O

(H2SO4)

In paint, dye, medicine, fertilizer etc. industries.

HCl

NaCl + H2SO4 →NaSO4 + HCl

Colourless, pungent smelling gas easily liquefied.

NH3 + HCl → NH4ClNa2CO3 + 2HCl → 2NaCl + H2O + CO2

3 : 1HCl HNO3

↑Is called aqua regia.

(HCl)

In manufacture of Cl2, NH4Cl, glucose.

COMPARISION OF PHOSPHINE WITH AMMONIA

S.No

Property Ammonia Phosphine

Resemblances

(i) Formula NH3 PH3

(ii) Colour & state

Colourless gas. Colourless gas.

(iii) Combustion Combustible in the presence of oxygen.

Combustible in the presence of oxygen.

(iv) Reaction with chlorine

Reacts with chlorine to form NCl3.NH3+3Cl2àNCl3+3HCl

Reacts with chlorine to form PCl3.PH3+3Cl2àPCl3+3HCl

(v) Reaction with halogen acids

Forms ammonium halides.NH3+HXàNH4XNH3+HClàNH4Cl

Forms phosphonium halides.PH3+HXàPH4XPH3+HClàPH4Cl

(vi) Reaction with Lewis acids

Forms addition compounds with Lewis acids(e.g.,BCl3).NH3+BCl3=H3NàBCl3

Forms addition compounds with Lewis acids(e.g.,BCl3)PH3+BCl3=H3PàBCl3.

Differences(i) Odour Characteristics ammonical

smell.Unpleasant smell of rotten fish.

(ii) Poisonous nature

Nonpoisonous. Poisonous.

(iii) Solubility Highly soluble in water. Sparingly soluble in water.(iv) Basic nature Basic in nature; its aqueous

solution turns red litmus blue.Very weakly basic; no action with litmus.

(v) Reaction with CuSO4

Gives blue solution of the complex compound[Cu(NH3)4]SO4.CuSO4+4NH3à[Cu(NH3)4]SO4

Gives a black precipitate of silver phosphide.3CuSO4+2PH3àCu3P2+3H2SO4

(vi) Hydrogen Bond

Hydrogen bonds are present in ammonia because of which it is an associated molecule in the liquid state.

Hydrogen bonds are not present in phosphine.

(vii) Reducing character

No reducing property. Phosphine is a reducing agent.It reduces AgNO3 into Ag.

Comparison of properties of White and Red phosphorous

Property White phosphorous Red Phosphorous

(i) State Translucent Brittle substance(ii) Colour White, gets yellowish on exposure to light Red(iii) Odour Garlic like odour Odourless

(iv) Hardness Wax like soft and can be cut by knife Hard(v) Poisonous nature Poisonous Non-poisonous(vi) Solubility Soluble in CS2 Insoluble in CS2

(vii) Ignition temperature About 303 K; burns spontaneously 543 K, burns only when heated

(viii) Stability Unstable, gradually changes into red phosphorous Stable(ix) Phosphorescence Shows Phosphorescence No Phosphorescence(x) Action of air Burns in air producing forms of P4O10 Does not burn in air(xi) Reactivity Very reactive Less reactive(xii) Action of chlorine Burns readily in Cl2 forming PCl3 and PCl5. Combines with Cl2

only on heating.(xiii) Action of hot NaOH Phosphine is evolved No action(xiv) Action of CuSO4 Copper is precipitated No action.

Difference Between Rhombic And Monoclinic Sulphur

Rhombic Sulphur Monoclinic sulphur1. It is common form of sulphur

andIs stable below 368.6 K

1. It is stable between 368.6 K to 393 K

2. It is amber coloured crystalline solid.

2. It is dull yellow needle shaped solid.

3. It melts at 385.8 K. 3. It melts at 392.9K.

4. It is insoluble in water but soluble in CS2

4. It is soluble in CS2.

5. Its density is 2.07 gm./cm3 5. Its density is 1.95gm./cm3

Comparision Of PCl3 & PCl5

PCl3

PCl5

PREPARATION P4 + 6Cl2 à 4PCl3

P4 + 8SOCl2 à 4PCl3 + 4SO2 + 2S2Cl2

PREPARATION P4 + 10Cl2 à 4PCl5

P4 + 10SO2Cl2 à 4PCl5 + 10SO2

PROPERTIES It is colourless oily liquid and hydrolysis in

presence of moisture PCl3 + 3H2O à H3PO3 + 3HCl It react with Organic compounds containing

OH group. 3CH3COOH + PCl3 à 3H3COCl + H3PO3

3C2H5OH + PCl3 à 3C2H5Cl + H3PO3

It has a pyramidal shape in which

PROPERTIES PCl5 is a yellowish white powder and

in moist air, it hydrolysis to POCl3 and finally gets converted to phosphoric acid. PCl5 + H2O à POCl3 + 2HCl POCl3 + 3H2O à H3PO4 + 3HCl

It reacts with organic compounds containing -OH group converting them to Chloro derivatives

CH3COOH + PCl5 à CH3COCl + POCl3 +HCl C2H5OH + PCl5 à C2H5Cl + POCl3 +HCl

phosphorus is sp3 hybridised It has a Trigonal-bi-pyramidal shape in which phousphorus is in sp3d