Electronic configuration, Physical and chemical properties of halogens including their pharmaceutical applications.

1. Written By
Department of Pharmacy
University of Rajshahi
Rajshahi-6205, Bangladesh

2. I
I;
.... .:--;:=-.::~:..~·.'":""·~·- - • ··-· ~-· .•• ' •.
....:. -·-·::.:::-r~.·:o-~::;;,.-::-=:·..,. '-'-~--~ __ .,:,:. __ p••· ;..,;_,,__.__..-, ••••.
-~ !-' ------·--·-------·
Physical properties of Halogens
Some physical properties are discussed below:
I. Occurrence: These elements do not occur in the free state. But in the combined stale they occur fairly (c11rt;flJfil1
abundantly (91~91W1t'I) in nature. v
These configurations show that all the halogens have seven electrons (ns1np~) in their outermost shell. Since the
additional electron in these clements enters the p-orbital of the outermost shell, these are called p-block clements of the long
form of the periodic table. · -
Elements Atomic number Electronic confi uration Valence shell electronic configuration
F 9 ls 2s 2p· 2s· 2p·
Cl 17 I s2 2s1 2p6 3s1 3p~ 3s2 3p~
Br 35 ls1 2s1 2p6 3s1 3p6 3d10 4s1 4p~ 4s! 4p~
I 53 ls1 2s1 2p6 3s2 3p6 3d10 4s1 4p6 Jd'0 S~1 Sp~ Ss~ Sp~
At SS ls2 2s2 2 6
3s2 3 6
3d10 4s1 4 6
4d10 4f1~ 5s1 S 6s! 6 s
y/ l lscd to prepare soap suspending mid rmulsifying ageut.
(!) Magncsinm tri silicate ..
• It is used as an iu~tacid to neutral ize excess amount of HCI into stomach.
/it is also used in anti- drug toxicity. . .
~Magnesium tri silicate (Hydrated) acts as suspending agent directly without help of any other compounds and
also acts as thickening agent in producing of chocolate.
_.(d17 - 8. S% Mg(OH)z in water is called milk of magnesia. It is used as laxative .
..-(rj MgSO~
1ls
used as laxative.' ·
rn MgC0.1 . , . ·
• It is used as an a~itacid and mild laxative (9ITT!~ ~ ~ l!l~.
• It is also used as food additive (~S~) Iii tooth itlid fnctl powder.
(g) CaCl2 -;.o/. . , . . .. .,, . ?. ~.~.ee.l~~c '~)r,od1 I• v Cht3'1f1 t
~5-:-10%s~1lut1or~ol.Cal1!1suscdm.tcta111dmnsc. ('D:jibi~Cjoj c.ai. 1n blood . · .
~ .. It 1s used lor maintatnmgthe proper heartbeat, l.0~ ,·HttefvJ4;i u~ocfi'o.i
0 ~b'Y' r/) <SM).c..uY.P.d,
(h) Calcium . . . . 1
,,
. .--.--Ii is tlte principle cation of the bohe hlarrow./Fof ti'eatment the osteoporosis (~ <rnQl $. ~ m lJNHO)
and rickets(~~~~-~ -s ~ m lli-sm) calcium P~?.~·i1ate is used. 7~ . ~<:>~ . w li.i'e-h / r,,
/' Use~ntidotf{f.1:3i ~ UTI'l'f ~~ ~~'1 t>f MA-gnesiuin. .
(i) csso, '1fo(.)-,~ P ~M. a.cflve /'n._!JJT~c/.len:.1- .. 'Y> ~ ':f t:t. ~~ 1'1>
.s-: It is used as diluent (~~~<t>hl<!i) in tablet. , ~ • T..J 1 '/) UMd ::fo (ff:;G> tMo.pp-1• cVrld.. l:l
. ~ Used as plaste•: clust 111 plaster of broken bone. (.· 6i. So~, 2 t/12_ CJ ~~ ::Jo •~-l~lt'e Jo.., 1M ~b1.
,kt'1Rad111m snits are used 111 cancer therapy. . / " P
(..k(Brrylli11111 is used as transparent in X - ray. ~ . ·. .
/ . ~ - (3fV)Ol::.J -ht>-~~()/~ ~i;>- .Lt3~ n-v ~/y;J{~
Question: How Mg(Olf)1 acts as suspending and emulsifying agent'?
Solution: Mg(OHh combines with other ingredlenls of'.a sojution to form complex. This complex remains suspend
(~) in suspension ~nd together in emulsion) These way Mg(Of.h~ acts as suspending arid emulsifying agent. '
~~ t= _chJ.vJ.e!rl-,; - ,·j 1'() ~nQJ~k r-ipG{)Q_ c:m,~mJ.~1'.g_.· ~ : ~'.:a,La8,~ ,·'YWJTX .°*1 t-uw'e. no
~·e.1:.Jo' ,·. e j-_a..v1'0 ! ~ 0 phc.oJtmc:C:*.~c~{Vl~~~a·"e'(!'C~JJe.. )Lt}/ A.·.s j-011' ::1 h.t'b'" ~~ori c~~<J4. '" "" pJlll;:
So -tp ~ c/.i.1.ubn+ .Gt ·11alogens 't m. phoo~c·euJr.~ o..clJ·v.e. oJ) .iJ ~) ~a.d-rl(Q p'(:IO.
to ~
4
Q11estio11rj)'..f1~tarehalogcnsandwl~ya.tctheysoca.lled'! b'wl_,'·6t_so,_.,·r;, ~1'0~@--t·c.~Ll--j.,·~-.-7.to)~(~.koLA ,J
Introduction: Group VllA of the periodic table consists of live elements which. are I· luori nc (I·). Chlori ne (Cl), Bron,111e ":)
(Br). Iodine (I)' and Astatine (At).,.+fhe elements F. Cl. Br and I ah:' collectively called Halllgcns.'.'st:itine v.rali ei!e~w~r~·d i1.1 mo(IJ.. P
I~ 11i1tJ...is ail unstable element ohaaionct1ve Ofigi~'O-r'J. 1'1';) 11-ot . . . ge,,i "----.. • • ~a..n
The term halogen is derived from the Greek halos (=salt) and genes(= born) meaning sal producers because nmst.~()'.~ ·
these elements exist in seawater. notably (~~l in the form of their sodium compounds. Thus M1e,;~ elemeRl!oi are r.:alv
HalPgeR, . _, N et'ci · ,
~onic confi uration: The electronic conf zuration of the atoms of halo ens are iiven below:
~- '.@1 '{ 1'f.l ct ~r'rn~11p/.Q.. ca.Jr·r:m oJ-' ::l. ht bon.() ·f'll.D.i~?<
I
r
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3. . 11. Metallic cCITT-~: With the decrease of inni":~tfon potentials frorit F to I. the tendency of these elements to ln~s an
.clectron to fom1/o1-cation increases. that is Fis not ahl€'t6 give F' cation while I forms 1tcation easily. Thus except I. 111hn
C:i hal0gens arc n01:show metallic character. We /'<'n.·,.,·,.:_'-th~. L • . , L ,A .L.. . . .
~~ : , ' . '%w.., ·-:::::;· rco-v-e dh.Q~ ~IJJ'-nc-:; ,oqv,aJ.CC-t.pJ cwi .e.xf..,,,.q e&ie:f.,.ori
cc:/-r.> j1'/! :.Irw;, ocfa....ft :: ;ti/Ac.1 Jltal/l n~.Ue()f. /;mt)~ " do be mt-.fcd)..i'r ::I h.t ~II) ~- ~v-e. cJ .kttJ..e,'flcy <ft;
TT>d-u ~tD1 J'l.. '
.. :.f- ..lov(')e_ ctn1 eL4c+Y""~.'fl--·, _So~. 1~ c}..t>n·J f}-f...ew , ~ 'fl.e:f:..Jali'c 'J,c{>dck,·, • TJ& c0~~= be!~ :::J·h.t.
~ ~":::;~,)~ ~ : •O 1~ ""' J;;,, o Jdt U 1~ '·''!¥'• · .O!i~•·; • ..;.Jij!J,<,~~CJ
BrCl
10.413
,~ ... , ., . "· ·... ' ;Pjf)::I~ fA.aKe. JRmc.Wne_j ::lo.a.c.cep-ie-f.o be" -v.e.r
@ TO. lonizatio~ potentials: The ionizati~n r~tcntials d.'° l~al_oge~:~,~~~ v~.rY high wlileh ihaieetesthet ~he ~ia1l?ge~s l~ave a .:
little tendency to loss an electron lo fo1111 X cation. These values pro~ressrvely decrease from F to I. as the atomic size of
these elements increases in the same order.
Heats of va orization Kcal/mole 1.60 · 4.4'0 ( . . 7.40 l0.40
Q.m.owrr;( cj AP!M rl!).qwJU..d ·e.cmv~n.J. cme. =o-.1.IL of ~I)'. efo.. ::thR. v~pOt,IJI t'f> ~d O vo..poWtth.a)-.'im"" .
«s< Heats of vaporizatien: The heals of .vapoii7.lHioti increase rroni F to I because as we proceed from r:- to I. the
· 1111ennolccular at1ract1on 111crease:i;. w ,·J-n d:-ha.- .nnui.a~ o -rr-.atY:> : . . _ · , ..
Elements 1' CL Br :1
Th_e_
(i) ~elting and boiling points: The melting and'boiling points of the halogens regularly increase from F lo I. ·~ l=.riom -fop
..tfldi@Rle!i tl~!M the attractive forces between molecules .l-'leealll@ pf'bgtessively ·mere prominenL(~. ~) !IS the meilt'elil€!'
. e::tltlz. r?'L-~T~ ot
mcreas 111 size ano mass. ,
Density ~""' C.· t.· 1.3 1.9 3.4 4.93
ia ouens are given e ow:
Elements Physical state '
Fluorine Gas
Chlorine Gil~
bromine Liquid
Iodine Solid~ .
'f5o..J tn« )(r;U,m/).er1 of g: & 012-e 171.cTIJi.Of>QI) i=: dop ::lo boo::f"m ;. b<J d-h.o_ e - ~ncl7Jlaoel> -moJJl. dham ,,{ lu l'>-1'2-e t>a ..d.et1&>1'±J ,;.,i. GJIP4!>t.l>
1,1 V: Densitv: As there is a chanl!e of stale from •as;to solid, hence densil i1icreases as we move from F to I.or:> -te boH°""
Elements F Cl Br I
'
~Physical state~ There is a change of physical state from gas lo' solid as we proceed from F 10 I. The physical stale or
I I b I '
increase rom to . Fnirm Jop .fc boffo-rn 'YlO· of ,,,.N..t.ll). '!''rcJlfUJ.tll'& ; o o .::Htz cLi·i.·l-M1a € l..""'1/!MI .Jiu n.a,,fonr..a
Elements F Cl Bt I
CQ.lalent radii (..( ) 0.72 I 1.14 L35
,'Jonie radii (A) 1.36 1.81 ~/1:1,~ 2.16.
@ ~·l' Ira; ~ml~ radii: With the increase of atomic riui11ber and atomic weight. covalent and ionic radii arc
ti F I ., ?tel (!)~
t>i.zu c.bv·""
~~l'rl
1'n~frLCJl'>e r?t 1
ha ogens. et"aur.i! 4'»> Jr,p fo bcrll- .-Jh.a. l}i7'1 o./ dh.q. cdam 1 '°nlOLtO/)['I) f>.o a)- w
Elements F Cl Br I
Atomic number 9 17 ; 35- 53
Atomic weight 19 3~.5 . ' 79.92 126.92
~tomic number and ;atoiniC weight: The atomic number and atomic weigh! increases on going lop 1(1 bottom of
I 8
Iodine - Dee violetChlorine - Greenish vellow
Bromine - Reddish vellow· Fluorine - Yellow
e,w.,,)
,. ··'I·)
t
,, JvtiV /olf2d u
' 13 brJ011.-b
F~1oru~M- -I> V!'olo.f -1..i(jhf (!-Ito!) fu(jh exid"a·l·rn
~ Ioir:Li~ (11
1 ! -·/') jellow 11 ,, low d
I .
I . Cr~ -b GLQU.m.£~ i~Jl-&0 .
I
ti:> iY' ~ P...Q_J..&...u~h-. bfr o urt> . .
. @<Odour: All tl~e halogen.s have very pungent (~) and unpleasant (~) odours. 1.r inhal~d cv~n. in. very small
quannnes, thd cause inflammation (~) of the mucous membrane of the throat and nose and seuous irntatron (~.
~9fli$1) of res~iratory duct. Large quantities may have fatal (~)effect. ': r
~Colou:r: All the halogens are coloured. Their colour is due to the fact that their molecules absorb light in the visible
region by meaps of ,w~i::h the oi~ i}eclrclt;are excited to higher energy levels. The amount of energy required for the
cxcitaliOrW~~a~~'~~owc~y (~'lff.T) from r to I as the size of the atom increases. Thus there is a progrc-sivc-
deepening (•l~l or colour orthehalogens from F to I.
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4. I
~-
F
Cl
11H is e
Molecules
~7 . ;:iaf>U.l';•'.1j fn.· .+.1).12. c4c iaa.M;ri1vrvl:c:f ·b O'Y.1d ·-M
~t~_s : r~Cl ~ rn'~ ~ t'd-tf) e- I~ R e.0
Br 5j ;, ·.,·· ,, , :: . · '. · '.
I ,:5i 11i' 1'.JI() od.tntFQ.J.U.v;h'-lf 0. }Ullpt.Jh';U;, d-o 4-h.Q. oJ-lwi e..o ~ Q .. •·
L...:-~~~~--~~~~~~~~~~~~~~~~-'-:....:....---,.~~.,..,.-~-.-~...,...=_J"-,-~-:----:-:--..,.....,..~~-.--~~....,--~....)
. • . . • , . <1> _, d"'-wr b O'fl.d ;fl.4-n-a.r 1-j.fh., d.u nu.OM ~·':'.j ::JM..
Question: Why the heat of dissociation of F~ is lo~er than tt)'f foo..-d ~'1
The lower value of heat of dissociation of F! molecule as compared to Cl2 molecule is due to the reasons naniely:
I. Due lo very small F -- F bond length in F! molecule, repulsion between the non-bonding electrons is yery large as
compared to other X - X bond lengths. this makes the F atqfus ii; i molecule repel (~ "<irm) each other and helps the
dissociation off, molecule into F atoms. · .
2. X- X bond in other halogen molecule is stronger lhl'lli F .: f bond in F2 molecule. This is due to the possibility 11f the
existence of multiple bonding in X - X bond involving d - .orbitals. . · . . · ·'
~ 18•. llea~ of_ hy~ration of X- i~ns: _Heat of hydration of~· ion (~H11) is the;a1nount of energy lib.erated in the process of
~onvertmg X 1~11on rnto hyd~ated X l•qt 1011. . Heo.1- o;j fj d;ui.:b O"rl ~!) CY'l'l d, ~ g, ze oJ-. ~ ,·ori •
-re;p ~ BcrH o rn =I> ""'1'>§>!{."1- X <al + aq ~ X (1q) + 11t[.; w 1 Jh. .±-he.. , In <:? Jl.JLO-OC 0 j t:l11'fa.. o-} ,'cm /-1 • oj • t+ d.Q OJtJW.t:ll~
r ~· +- J'"""' The value of ~H" becomes less negative as the size of ~he ~a~Hhatthe electrostatic interaction (f11~) of a large " ion
with water dipole becomes weaker than a smaller X- ion and he11ee the value of~Hh goes on decreasing.
@ 19. Ox,~d~tion - _ke.duction st8+te:. W~en a halogen at01i1 lii Its ground.stale c?.inbin~s with an cle~e!.1t_ o_f lesser
electronegat1v1ty than 1t, 1t show~~ ox1dat1on state. On the other hand when 11 combines with an element hilvrng gh·ater v~ ~
.. C.o'lld../fi"on~1i.0">el_cctronegativity:it :;ho1n; +L-*'3. ! 5 and 17 exidatioA stale. 'X~~3 ~ ?<-rs- ..) -x,-1"7-. Th.JI) t'I) ~ee~ oj ::J-~ 'moU.dok
r,J-o.J:Ji.. acc.c n d..i?j do .:1-~ h.u.NI, /'J 1t.u.1.ft- . . . . .
Question: Why F does not show any pos1t1ve ox1dat1on stale. while olher halogen molecules show?
. Since Fis the most electronegative element. it always shows -I oxidation state only. It does not show any positive
oxidation state. Cl, Br and I have vacant cl-orbitals ih their valence-shell and they can promote (~ <!Im) their s and p-
~ ~at of dissociation @f Xi molecules;.. Heat of dissociation (~H11) of X2 molecule is theamount of he~t required to
C/ dissociate X2 molecule in the gaseous staje into X gaseous atoms or to break X -- X bond in X2 molecule. · · J
t ~2 <~> + i1H" ~ 2~, . . '."' .- ..,.,,,. . , (>1.te-- 0 3..tN-- o:to-m 1-n c
.. &ond ener . Exce 11n for F2, Affd va e, decrease.from Cl2 tel 12../ f> .J.1u.. · · , ~..J_
lond tne to -: d-{) bott-oY» • l'l c
· Elements : .· Electron affinit
F E/7 •A.:&e. ahfloumd ~·Qf'!.QJt..j::J ~d Jo~ 3'.'7 T~ fl>-rj F .» ' ha.n od--Jv.r.~ ,J MM. TJ<DlJ ttt''le
Cl ..lloJ cd L . . . _,. 4-4-lu'o -Jhq_-e-,,, R. rCD.maJ'n ni>Ollll ~,.~ cumpa_cJ.--fo "'4.LA. .:/it..(i)I ,,_ _,
Br rruL1 ~"' rrm "° o. UrN 'Nlj«rrte C1A1.1'07!• Ao N;µ!Jbn j ~!"11
I
l1M) Q. ~ ~ q-o ed · e_....,, ,. r>-/toW!i> £,4. · • 8 eJ-h.en e- ~ ,·.J- r.Jv>k>F.> " "M--P.J"'·rm jonee ; J-h4iujo ~ a.
I J, 4 lf!.I) · ,
i
{ij 'J'(Sohibility: Th~ halogens are slightly soluble in wat~~ ~nd their solubility1• decrease from Cl lo I. F cannot be
dissolved in o/ater, sihce it decomposes H20 to liberating(~ <ilzj) 02 and some 0.1. The halogens dissolve much better than
H20 in many organic sol11e1-l~ lik@ CS1. ehlimifern~. ether eie. li'i ergeAie rolvents iodjne gives vigl~t eelgr, brQR'liR@ gi11cs
bffl11in c91or ~ncl ehlori.nf: gjvi's'~l~v, eolor. IA tl:ie grgal:iie seil ve11ishalogc11.1 Cltl!ll as ftee meleettlc 11~ iM ti1e gal< plme
•. ! . lo
~~ Diatoriiic nature: Halogens e'xis{ as covalent diatomic molecules (X2 molecules) in th~ gaseous, liquid and
~stalline states. These discrete (")11/<ll) Xt:..!nolecules are held together by weak van dar-Waals forces which explain the
volatile nature of these elements. The stability of di~tomic moleculestowards heat decreases from F~ lo I!. . . .
Ci)) •·' . f]t:> 1>1'ze 1'tn..c~ j11.b'm :}op Jo bofl~
~ 14. Electron affinlt : lectron affinit values decrease from Cl to 1.J
. . . .. .Sfv "'I) ,t/.,,N/ :lhf!J h'LVe r;u
M ., ~ . . 1
-~'(f.k.'1ll•/ _.i,, I •IY ,,-
V 11. Photoelectric effect: Electronic configuration ~f oYletmo~:t she!~ of halogen« i.s.. n>"~np~/lthcl lj./.;..4ere-iwe--.cwB-
.etectren:; in ot1lermrn;I :;hell. Sti it is impop·ihle to eject the electron from outermost shell and thus (hese metals are not show ·
any photoelectric effect. t-r-¬ //n- J wt>uld flu.;(- f.>chci()) ~· pho.do e~dm"c. eblftc::;l· . ·. • . -
' Jh£ ~dP/11~ '=fo ~am ~ofntrn i''I} -:1:/uM or.,(jen·muJJt: r.>J...!)j 1
·".'t'l'lrl d.W hef? O<
W ~ Elec.tronegativity: Halogens have'largc values of electr·o.negativity. T.hese vall1cs.· decrease as we pr.oceed from F to
'T(n the zrou .Al) -fPrrm "1op .J-oJpoflv-m w•.ffL .Jfui. r'ri..~1t.flaf:>lHrlM-·J:.oj am ~'{ .~- tYNuJ -d~ f'-r·;.e.. of .+Ju qj<nrW) r'-lt c1ta[;l).ya.,,.J -+
· a_lf-;uu f;
Elements F Cl Br I ·
Electrone ativit 4 3 2.8 2.5 J ,
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5. Qy.estion: Explain that. formation of hydracid wil I decrease ifom Fluorine to iodine.
J. Formation of hydracid: All the elements of halogens coh~bine With hydrogen and form hydrogen halides which are
called hydracids or halogen acid~-:J.:he affinity of these elements, to form hydracids decreases from F to I. Thus F2 combines
with H2 explosively(~~ m) aird.even in dark, Cl1 reacts with l-t1 in diffused (~ ~ Cl1'811l) sunlight, Br1 reacts
with H1 only dn heating above 500 PC whiien--reac.ts..wit!!J:!.r~;on heating a11d presenc~of Pt as a catalyst.
; ;· M -+- ~ --P *--/+( ~ , ·.. · ·.·· · . ~fwm.__ eh_~·!:> -R.M-e e~clrio
, F2 + 1-12 ~ 2HF; Cl2 + .H2 ~ 2HCI g)
· Br2 + 112 ~ 2HBr; t2 + H2 -~ 2Hlr .· ftJdJw8Cm AM ~d-""" poet'h.111'/-:;·
·. . ' .· . · 7Ju, SU.C<t.Jlj & joJ'lt:> ~ C!.&mPOr:JJYtd /':>,
~xidation reaction: Oxidations by the halogens are the important arid faiuiliar reaction. Fluorination is the most · . ,
vigorous and i~dination is the least vigorous. but this depends on the materials with which the halogen reacts. Halogens have
_!endency to atfraet electron. So t110'.J!Ccept elect ther com ounds _and oxidize those of c 1 (Htnds:-Generally the
_reactions are t~nned as halogination._I.b.Y.S.L..oxidizes..C:iffi,.!2J!roduce HF an · FfUorinlysis and Cl ox1 izes C. .z..!_o ·
CTJt and Sf~· i"'L _ . ·, ....
' ' ·r-· l. 0 -+3 -J_
~ C2H6 + 7F = 6HF. + 2CF4 -<? Q,I~ -t r i: ~ (;: F.l1 /'. _)
: CS2 + 3Cl2 = S2Cl2 + CCl4 ' VL ,__,....'J..:_ • -e ~ ._G,/ e - ~cr;c'LID ff'/' (51
: . . - o"':j d.i.'r.}i (lq 0-l!l-en:i
_/:F m' t' f 'd' · E . q!~ . . ....._) .-.J _,
V.. tor a 1011 o oxyaci s: xceptrng F2• all other halogens fonn oxyacrds. These are mainly of four types -- HXO.
HX02. HXO, and HX04. In the se1ies of oxyacids of the same halogen in different oxidation number the acidic characlcr <If
of such acids increases with the increase of the oxidation number of the halogen.
'~. 02 495 Ch 237.38 ")f..-
r H 431.89 Br 190
· I 148.50 j4t?-2~:;i.::,:><2-'5-(<TI'.
' P' · --r:~ e>f M.loee-nl) 11) ,..c>1~ ..}._ow 12o'l7lpooild ·=It> 0JN>1 dJ~wlQ Nz_ o t-
~~'NI" ·".., Since halei::eA~; htMolOI'> •11lt1<.!< of!dissoeiation energieSAthu~jJjs much easier for these molecules to dissociateseto X
1 O-t)0 ~ ~~<",)' atoms and reac! with ~ther substanc~s 1~1ore readily m;e0Al13are~otlier diatomic molecules like N2• 02 and H2. jProved~
i a,(' ,#' . (b) B.c~a1m· c~ ~ electron affinity ~of halogen atoms.,halogens hav~ a st~ong tenden.cy to ad<1tlectron to to1111
:, e..)~ ..'v x= ion. Th.JI) >< ,,yn rrJJ_~ ~a~,., 'e,"o1~ 6~ri·~ cunr11:::.;uz_'f-f!!!::J;...,~A I· 0/' V'lruo~ •• .,., ' ' '
,; f/2&c;6.'c:m w•'Jh..._µhereactivity o~ halogen atoms d~_crea:es as we proceed frohi_F to I. For ex m le .. luorine decomposes l:l...:!Q vigorously
· /jJo:Js;_.ri . r- even in dark. Chlorine and Bromine decomposes HiO in sunlight ti · o me does not decompose H20 at alL_ ...
~-- , _&.. /= r's JfuL -mod
~ 2F2 + 2H20 4I-iF1 + 02 ; Cl2 + i-120 HCIO. + HCI bt;ica.u.~ ,'-f ,-5 7fT.¥'17'-aJl
,. " . . . . , .. . . So e- Lm.o r.J~ bO"llcl..a-d Jo N
Br2 + H20 .. _,,.__.___ . -~ HbrO + HBr; . 12 + lt20 , No Reaction ,, +' .· . --tr. ,. · ' CU;t}La(; r"O'ty) Jvll I f:. /n DJ"IJ! J. fta.n
/. Formationof lonk~ompounds:,Halogens react with m,etals to fonn ionic compounds. All the metals react with
halogens at various conditions and with different rates.~ol11l i11elal~very vigorously and others slowly under heated
conditions. The rate of Ionuation-of-ionie-compouodsis decreas& bn going F to I as the size of aiom and anion is increase
j from F to I_,_._ ·
-t--i 2.l'Ja + Clz,.~ LNaCl
Chemical properties of Halogens 'l<ectc.-l-Ni!J cj Wojem ~!') O'n d-tu.(j)di's5oci
Some chemical prope11ies of halogens are summarized belowi. enoi 'j TlfU/uQw_d do ~omv enl ::f ks: d.tolom.r'c.. NJ...o
'1~ ! • . . --:nem o ccforru C. ~d (!]) ::/k e l1u_.-/-Yl'dna-Hr:,..; 1y 'JW..C(w
~~·;.hon: Proof that, halogens arc more reactive thanOxygen. Nitrogen and Hydrogen. be CUl.- cuuo'>'l.. ·
V.. Reactivity: All' the halouens are the most reactive elements. The main reasons for their extreme reactivity arc: :><,_
(a) Disso~iation ener ie; of halo en molecules and other diatomic molecules I ike N,.02 and H, are:
20. Oxidising property: A substance that has a tendency to accept on~ or more electrons is said to show oxidising
property. The halogens, due to high electro~ affinity values. have ~ great tendency to accept an electron and hence act as
strong oxidizing agent. The oxidizing property decreases from Fi to 12. !1.i ! • , ,
electrons to the vacant d-urbitals in case of excited states. which make it possible for these elements exhibit higher positive
oxidation states of 13 .+ 5. and 1 7.
Since F atom has no d~orhital in its valence shell. it cannot have any exciliod state and consequently(~~ '511'11~) cannot
exhibit any of the higher oxidation states.
Md.
Imran
Nur
Manik
Page 4 of 6

6. (a) KI is used as an expectorant.
(b) It is used in gaiter disease.
(c) It is a component of tincture iodine.
(d) It is used in larger doses for hypothyroidism.
(l') It also used as an anti fugal agent.
(v) LiCI: LiCl 'is used in air conditioning system. In air conditioning plant in form or 35 - 40% aqueous solution is used
for humidity control.
(vi) Cacti
(a) It is used lo prevent hypocalemia tetani disease.
(b) It is used for the heart contruction and relaxation mechanism,
(c) 5 - 10'% CaCI~ solution used as intravenous solution.
(d) It alsb used for preventing milk of magnesia poisoning,
KCI is used as diuretics thiazide which increases.the urine excreation.
KCI is one of the major component of ORS.· '
To prevent hypokalimia disease KCI is used.
It is used in paralysis, mysthemia gravis, menieres disease.
It acts as an antidote in digitarln intoxicatibn.1
- /.!
(iv) Kl
d3t>harmaceutical inlportance of halogen
~i) Chlorine: ct· i,on_is,,the principlefanion of extracellular-fluid. Due to deficiency of C!, hypochloremia disease is
created. For this salts ercr (~aCI. KCI) are used to prevent hypochloremia. ·.·.· · ·
(ii) NaCl
(a) NaCl is used to pr~.~en• hyponaremia disease. .
(b) 0.9% solution ofNaa1 is -used for tonicity adjustment pharmaceutical products such as eye drop, parenta
injection preparation etc. .. ; .
(c) Isotonic solution of NaCl is used fo inigdtion. .
(d) Hypertonic solution of NaCl is used to prevent 11ypoedema.
(e) 6% solution of NaCl used as preservative.
(0 NaCl is the principle component of ORS.
(iii) l<Cl
(a)
(b)
(c)
(d)
(e)
3F2 + S -4 SF6: Cl2 + 2S 4 S2Cl2
./}' ZCl2 + S ~ SCI~
J.6".' Reaction with 112s: Halogens react with H1S normally. In this reaction halogen oxidizes sulfur atoms and
precipitates it from H1S to solid sulfur and combine with H to form halogen hydrides.
· . Cl2 + H2S ~ iHCI + S j, . . . .
~~a_ d-t"on -e 0 "L-
~rfo~mation of binary halogen-oxygen compounds: Halogens do not combine directly with 01. I lowever, binary
halogen-oxygen compounds cak be prepared by indirect methods. Exampl'1frof such compounds are OF2• 01F2. Cl10. CI02
etc. F being more electro e rative than oxygen, OF1 and 02t2 are called fluorides ofoxygen and noJ oxides of fluorine.
~ ·-~~~-'-~~~~~~~ -~~~~~~
•
Q_ · -» 1-latJ.eml) cuvn.joJ-vm ben&t> ~ eacA od-ha11?
? hn J~ v ac_CUl:J 4 01th/Ja) exeep.J J J.uru~ ; o.fh.Qn ha_uj~o CCU1 be
(:_~ :Jo . :fhs: X -t-J-' ?Cf°g, 'X -t-i; _, 7( +;;; Dlcd€ • B v.f f:' d-o"fl' J Ko."~ va.c__cOJR<I
t Je>etj.,,'<:f okm.acl M x-1 /;YoJ c_tvnn'd- * boonckcl _,{;_!a_:;]Jv.O • (.:'"-at:>~ ft-1 oArd..t. ·
.K." Formation of intcrhalogcn compounds: Two different halogen atoms. due to the difference in their
electroncgativity values. combine with one another to fot·n1 a number of covalent compounds which arc called interhalogcn
compounds. These arc of~ypcs namely AB. AB,. AB~ and AB7 where A and B arc two different halogen atoms.
Cl + F ~ di<=, Clf,, df~.Cii"1 ./ . . .
Yf ormation of polyhalides: In some cases halogens combine with simple metallic halides that is KI, KBr, CsCI etc.
andfom1polyhalideslikeK'[h]'.K[Br,j·.cs·[clF4rett.
1
·. ~ ,..,'.f··-.i J- ·2_-f-Kl ~ 11'-L ~
~e~ction with phosphorus: Halogens react with phosphorus to givephosphorus halides. There are two types of
reaction held among phosphorus and halogens. In the presence of excess phosphorus the product will be phosphorus trihalide
and in the presence of excess halogens the product will be phosphorus pentahalide.
: 3X2 + 2P ~ 2PXJ [Excess Pl . '
!. SX2 + 2P ~ 2PX~ [Excess halogens] , _1 A .• . d. 1.~u."-" .1 . · . f-1> .L'!0!.
. r .. 4 di'ffeil~ Nt.J-d~ 01.'v-4 1$.fQF'l(;Jr:.• C()'Yn.pOIMQ.
~ction with sulfur: Halogens react with sulfur~ give S1X1• SX.1• SX6 etc. type compounds. Thus Cl1 react with
sulfur to fortn S2Cl2• SCl4 compounds and F2 react with sulfur (o form SF,, compound. But 11 is less reactive and it docs not
react with sulfur.
Md.
Imran
Nur
Manik
Page 5 of 6

7. f
''
/
/
Srfve J ~'<Lt (
~
W~ a.,tJ",'O'/l.P~J •'n Woft.'P-
Aj U: 15 ~[.Q_ 1'~ waL-n
;----~-~~~-4--=-~~~l--.;:;;_~
~.pla-?<.- 1;C) -a:__ L r1"-.o:;fr •C11"'1.- ~ ve ~'!:J. ~G,y :ff> farn>7
t---------.:J....;.._u----~--l~(!.!...{'.2,.,16'3- _:. (Fe. F. -~ Co""f> IJ..r1'0
/-kt-a NJJ~JJ.__ 10n~ ~ ~5J . s-r-b
i-----~.~~~~~'-~~~--1-- -
p0~ Nl_ill 1)oY>• }. fonmt:>_ Of.ijo'' ~r'~ oi; I hnn">•f) on p(Jr!.~·f'.l~ 1·.,
1------------------1~-- -! ~c;J_Cl/ll.~ _ __ _ po~ lQU~ -#Vnr>t.o.frim
5,JµJ,,'),,'{_j +_~.>tiwoltPI I n5o~(L (oJ.uhlo .
I
-L
r .
'!.
/
l
I
I
Md.
Imran
Nur
Manik
Page 6 of 6