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Master

CardChemistry

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The s-Block Elements

Prepared By : Prakhar Tandon

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Chapter s%mmary

& Characteristic properties of the s-block

elements

& 'ariation in properties of the s-block

elements

& 'ariation in properties of the s-block

compo%nds

& (ses of compo%nds of the s-block elements

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Characteristic properties of s-

 block elements& Metallic character 

& Lo) electrone!ati*ity

& Basic o+ides, hydro+ides

& #onic bond )ith fi+ed o+idation states

& Characteristic flame colo%rs& eak tendency to from comple+

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Metallic character 

& .i!h tendency to

lose e- to form

 positi*e ions

& Metallic character

increases do)n both

!ro%ps

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Electrone!ati*ity

& Lo) n%clear

attraction for

o%ter electrons

& .i!hly

electropositi*e

& "mall

electrone!ati*ity

/ro%p # /ro%p ##

Li 012 Be 013

 Na 214 M! 015

K 216 Ca 012

Rb 216 "r 012

Cs 217 Ba 214

r 217 Ra 214

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Basic o+ides, hydro+ides

8+ide .ydro+ides

Li58 Li8.

 Na58,

 Na585

 Na8.

K 585, K85 K8.

Rb585,

Rb85

Rb8.

Cs585,

Cs85

Cs8.

8+ide .ydro+ides

Be8 Be98.5

M!8 M!98.5

Ca8 Ca98.5

"r8 "r98.5

Ba8, Ba585 Ba98.5

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8+ides, Pero+ide, "%pero+ide

Reaction )ith )ater:

8+ide: 85-

 ; .58→ 58.-

Pero+ide: 855- ; 5.58→ .585 ; 58.

-

"%pero+ide: 585- ; 5.58→ 58.

- ; .585 ; 85

  11 11 5-:8:8:

  11 11

Pero+ide ion

  1 1 -

:8:18:

  11 11

"%per o+ide

Li does not form

 pero+ide or s%per o+ide

Li585 → Li58 ; < 85

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.ydro+ides

/ro%p #

hydro+ides Li Na K Rb Cs

$ll are sol%ble, base stren!thincrease1

/ro%p ##

hydro+ide Be M! Ca "r Ba

"ol%bility increase, from

$mphoteric to basic, base stren!th

increase

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Predominantly ionic )ith fi+ed

o+idation state/ro%p #: Most electropositi*e metals1

  Lo) first #1E1 and e+tremely hi!h second #1E1

  orm predominantly ionic compo%nds )ith  non-metals by losin! one electron1

  i+ed o+idation state of ;01

/ro%p ##: Electropositi*e metals1  Lo) first and second #1E1 b%t *ery hi!h third

  #1E11 .a*e a fi+ed o+idation state of ;51

  Be and M! compo%nds possess some de!ree

  of co*alent character1

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Characteristic flame colo%rs

 Na; Cl- 9!→ Na 9! ; Cl 9!

 Na9!→  Na= 9!

>Ne?@s0 >Ne?@p0

 Na=9! →  Na9! ; hυ 9364nm, yello)

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lame test

.Cl9aA sample

Li deep red

 Na yello)

K lilac

Rb bl%ish redCs bl%e

Ca brick red

"r blood red

Ba apple !reen

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eak tendency to form comple+

s-block metal ions ha*e

no lo) ener!y *acant

orbital a*ailable for

 bondin! )ith lone pairs

of s%rro%ndin! li!ands,

they rarely form

comple+es1

Comple+ formation is a common feat%re of d-block 

element1 e1!1 Co9N.@@;

Co

:N.@

:N.@

 :N.@

:N.@

.@ N:

.@ N:

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'ariation in properties of

elements& $tomic radii

& #oniation enthalpies

& .ydration enthalpies

& Meltin! points

& Reactions )ith o+y!en, )ater, hydro!enand chlorine

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$tomic radii 9nm

Li 21035 Be 21005

 Na 2106 M! 2102

K 215@0 Ca 21047

Rb 215DD "r 21503

Cs 2155 Ba 21507

r 21572 Ra 21552

Li

r 

Be

Ra

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#oniation Enthapy

/ro%p # 0st #1E1 5nd #1E1

Li 304 7@22

 Na D4D D32

K D06 @272

Rb D25 5@72

Cs @7 5D52

/ro%p # 0st #1E1 5nd #1E1 @rd #1E1

Be 422 072 0D622M! 7@ 0D32 77D2

Ca 342 0032 D4D2

"r 3D6 022 D052

Ba 325 4 @@42

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#oniation Enthalpy

Li  Na

K Rb

Cs

0st #1E1

@22

D22

322

22

322

0222

0322

5222

Be

CaBa

Be;

Ca;

Ba;

0st #E

5nd #E

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#oniation Enthalpy/ro%p #

01 .a*e !enerally lo) 0st #1E1 as it is )ell shielded

from the n%cle%s by inner shells1

51 Remo*al of a 5nd electron is m%ch more diffic%lt

 beca%se it in*ol*es the remo*al of inner shell

electron1

@1 #1E1 decreases as the !ro%p is descended1

  $s atomic radi%s increases, the o%ter e is f%rther

a)ay from the )ell-shielded n%cle%s1

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#oniation Enthalpy

/ro%p ##

01 .a*e lo) 0st and 5nd #E1

51 Remo*al of the @rd electron is m%ch more diffic%lt

  as it in*ol*es the loss of an inner shell electron1

@1 #E decrease as the !ro%p is descended1

D1 #E of the !ro%p ## is !enerally hi!her than !ro%p #1

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.ydration Enthalpy

/eneral trends:

01 8n !oin! do)n both !ro%ps, hydration enthalpy

  decreases1  9$s the ions !et lar!er, the char!e density of the

  ions decreases, the electrostatic attraction bet)een

  ions and )ater molec%les !ets smaller1

51 /ro%p 5 ions ha*e hydration enthalpies hi!her   than !ro%p 01

  9 /ro%p 5 cations are do%bly char!ed and ha*e

  smaller sies

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'ariation in Meltin! Points

"tren!th of metallic bond depends on:

01 #onic radi%s51 N%mber of e- contrib%ted to the electron sea per atom

@1 Crystal lattice str%ct%re

 Note: The e+ceptionally hi!h m1p1 of calci%m

is d%e to contrib%tion of d-orbital participation

of metallic bondin!1

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Reactions )ith o+y!en

"-block elements are stron! red%cin! a!ents1

Their red%cin! po)er increases do)n both !ro%ps1

9$s the atomic sie increases, it becomes easier to

remo*e the o%termost electron

"-block elements reacts readily )ith o+y!en1

E+cept Be and M!, they ha*e to be stored %nder liA%id paraffin to pre*ent contact )ith the atmosphere1

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Reaction )ith hydro!en

$ll the s-block elements e+cept Be react directly )ith

hydro!en1

  5Na9s ; .59!→ 5Na.9s

  Ca9s ; .59!→ Ca.59s

The reacti*ity increases do)n the !ro%p1

8nly Be.5 and M!.5 are co*alent, others are ionic1

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Reaction )ith chlorine

$ll the s-block metals react directly )ith chlorine

to prod%ce chloride1

$ll !ro%p # chlorides are ionic1

BeCl5 is essentially co*alent, )ith comparati*ely lo)

m1p1

The lo)er members in !ro%p ## form essentially ionic

chlorides, )ith M! ha*in! intermediate properties1

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'ariation in properties of the

compo%nds& Reactions of o+ides and hydro+ides

& Reactions of chlorides

& Reactions of hydrides

& Relati*e thermal stability of carbonates and

hydro+ides

& Relati*e sol%bility of s%lphate9'# and

hydro+de

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Reactions of o+ides and

hydro+ides01 $ll !ro%p # o+ides reacts )ith )ater to form

  hydro+ides

  8+ide: 85- ; .58→ 58.-

  Pero+ide: 855- ; 5.58→ .585 ; 58.

-

  "%pero+ide: 585- ; 5.

58→ 58.- ; .585 ; 85

51 $ll !ro%p # o+ideshydro+ides are basic and the basicity increases do)n the !ro%p1

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Reactions of o+ides and

hydro+ides

@1 /ro%p ## o+ideshydro+ides are !enerally less basic

  than /ro%p #1 Berylli%m o+idehydro+ide are

amphoteric1

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Reactions of chlorides

01 $ll !ro%p # chlorides are ionic and readily

sol%ble in )ater1 No hydrolysis occ%rs1

51 /ro%p ## chlorides sho) some de!ree of co*alent  character1

Berylli%m chloride is co*alent and hydrolysis to

  form Be98.59s and .Cl9aA1

  Ma!nesi%m chloride is intermediate, it dissol*es andhydrolysis sli!htly1

  8ther !ro%p ## chlorides F%st dissol*e )itho%t

hydrolysis1

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(ses of s-block compo%nds

& "odi%m carbonate

 H Man%fact%re of !lass

 H ater softenin!

 H Paper ind%stry

& "odi%m hydrocarbonate

 H Bakin! po)der 

 H "oft drink 

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(ses of s-block compo%nds

& "odi%m hydro+ide H  Man%fact%re of soaps, dyes, paper and dr%!s

 H  To make rayon and important chemicals

& Ma!nesi%m hydro+ide H  Milk of ma!nesia, an antacid

& Calci%m hydro+ide H  To ne%tralie acids in )aste )ater treatment

& "tronti%m compo%nd H  ire)orks, persistent intense red flame

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I%estions To PracticeJ

I101 hat are common physical and chemical properties of alkalimetals

I151 Name the alkali metals )hich form s%pero+ides )hen heated ine+ess air

I1@1 Name the metal )hich floats on )ater )itho%t any apparentreaction )ith it1

I1D1 Mention main constit%ents of Portland cement

I131 hy does Br sho)s similarities )ith $l

I11 /i*e t)o ores of M! 1

I171 .o) does !yps%m acts on cement

I161 hy is K85 parama!netic

I141 hat is fly ash

I1021hat is dead b%rnt plaster