Electronic configuration, Physical and chemical properties of alkaline earth metals including their pharmaceutical applications.

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

2. --·---~-----~· . -- . . .
.. • 4fl _.,,,._.... .. ;·-···~•o:.'r.'i--~
----- +~.----)~ ;,,' ~. J •• :~ ..
. I
i
.
..._._.:;; , -----~.._..,.,_
5. Colour and magnetic properties of Mu ions: Since the outer shell electronic configurations of 112+ ions arc
similar to those of inert gases (s2 or s)p'' configuration). these ions have 110 unpaired electrons and consequently arc
diamagnetic· and colourless.
~4. 1lo:li1ic volume, atomic and ionic radii: Because of the addition of an extra shell of electrons to each clement from
Be to Ra.~he atomic volume increases from Be to Ra. With the increase of atomic volume the atomic and ionic radii also
increase from' Be to Ra. The smaller values of atomic radii result in. that the alkaline earth metals are harder, have hiuh
densities and hi her nielti 1 • oints than the alk Ji metals. '
Elements 1 Be M Ca Sr B
1*1& 1571.*''"
BaElements Be M .Ca / Sr-
Elements Be C'a Sr l3a f<C(
Dcnsit (gm/c.c.) 1.8 1.55' ~ .!2, Ga ·9' ~ 6 · O
/ hr s ~(";a;;;;~ • _71;~~i1q - ·
V Melting andjboillng points: Melting and boiling points of these elements don't show any..regular trend. However.
Tn t!!fY(nfY/;"J the melting and boiling points of thes~ metal~ are higher than those of alkali metals. This is because the alkaline earth metals
have two valence electrons and are much stron I bonded in the solid state than the alkali metals.
Elements Atomic n Electronic confi urntion -- Valcticc shcll clcctronic conflgurn1io1
Be 4 Is 2!! 2s
Mg 12 ls2 2s2 2p6 Js2 3s2
Ca 20 I s2 2s2 Zp6 3s2 3p6 4s2 4s2
Sr 38 ls2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s2 5s2
.._· Ba 56 ls2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d111 5s2 Sp6 6s2 6s2
Ra 88 ls2 2s2 2 6
3s2 3 6
3d10 4s2 4 6
4d111 4f1~ 5s2 5 6
Sd111 6s2 6 6
7s2 7s2
~
These configurations show that the ultimate shell of these elements has two s-electrons (s2 electrons) while the
0) penultimate shell contains eight (s)p'' electrons). When the two s-electrons of the valence shell are lost, alkaline earth metals
~ are converted into M2' ions which have inert gas configuration. Since the additional electron enters into the ns orbital. lh<;.sc
~ elements are called s-block elements. · ·
j
Physical properties of Alkaline Earth Metals •
Some of the ph~~ical properties of alkaline earth metals are given below: . . l
Physical state: TI1e elements of this group have a grayish white(~~) luster(~~) when freshly cul and art·
nalleable and ductile.
1
'/? B<i--7> CQ ,,f;- 69 ;;:___~ S,'ze ~
Questi~n: Why a_lk.lline earth m~.tals are denser(~~~) than alkali metals'!/ ~.~ s.", e-; ="::». ~ <1""~C
~Density:Density of these elements do not show an>' regular trend (~). Irregular vartation of [l;ie-dens1ty is due -
to the difference in crystal structure of these elements. ~,1>c-h1paring W-l@ dea:1iti r tin" rl•~witl~~aikali metals. ~ 1-ha.
~ee1~ that these elements are de¢;er rhan thobMkali metals in>the;~ame period. This is due to the fact that. the elements of
group HA are !fou~dmore tightly due to their greater nuclearcharge and smaller size. Density decreases s.lightly (~
~) upto Ca. after which it increases.
Alkaline Earth Metals
~rorf:1 (M"1~1 .w1 21 '"f5T<rr4, v~i .'-! qr(j, (?
•
0
• 1t
Introduction: Group J1A or the long [orm of the periodic table consists or six clements which are: 8<•1:11lli11111 (/JeJ:
Mfl~11esi11111(M~). Calcium (Ca), Stro11ti11111 (Sr), Barium (Ba), arid Radium (Ra). (c<r<ITT lf~ <J>lill ~R <fll1"rl ~)
The oxides of the three metals Ca. Sr and Ba were known much earlie1~111n the metals themselves and were called
alkaline earths. since they were alkaline in character !lnd_~l~!!ITegJ~'-~~~-s'!I)) [n n_11Jlirc as earths [lil11e (C'aO),strontia (SrO) J.
Later (<>iiM'5Tc~). when C'a. Sr mid Ba were discovered. they were named alkaline eai1h-meiaTs-:--- -- · · ·- ·- ·- - · · .
"){LonieConfiguration: *
The electronic configurations 11f the atoms of alkaline earth metals arc given in till· lollowing table:
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3. ,1
~ . 3. Formation of hydroxides: .The hydroxides of alkaline earth metals are obtained by the reaction of the melals or
; their oxides witli water. ·
( '•
-c '/ c-e~i(~(, 16
(b) Peroxides: The peroxides Of these metals can be obtained on heating the normal oxides with 02 al high temperature.
2Ba0 + 02 4 2Ba02
Be and Mg don· t give any colour lo the name. This is because the atoms arc smaller and hence their electrons arc more. . 11' I
strongly attracted by the nucleus, Hence these electrons are not excited to 'the higher energy levels by the energy of the flame.
10. Distortion I J>olllrising power of M~' cations: In this group the ionic radius increases from Be to Ba. Whereas
(~ ~~ ~'IT ~ <A1) the ionic charge remains the same. Therefore. polarizing power of M2' cations decreases from
Re2' to Ra2•• In general, smaller ionspnlarise the ions 1;nore effectively than the bigger ones. Therefore. Be2' has a tendency __,,,,~
to form covalent compounds. · / :'• · · -. . . . · ··~v,. · . .
11. Conductlvitjt: Since two valence el~ctrohs are tree to rti~v~;throughout the metal structure. the alkaline earth metals •
are good conductors .of heat and electricity. .I ~·. !
.J)l?l)ecomposition temperature of their carbonatesr All(the carbonates decompose (~ ~'8ll1) on heating at
appropriate temperature. evolvingJ!S~<>tfu ~~) C02• ..
. . M~.:~ ~ C02 + MO;,..
The stability of the-carbonates of these metals increases 011 hioving down the group. This is illustrated (~ ~ <rn~rn
~) by the values of the decomposition temperatures of lilese tlath-~R~te.~ as given below: · . . _
Com ounds :;.,... Decom '69 tlen tern eratures °C)
Sr - Crimson Ra;-;,Red
y9. Flam~ colouration: In the name taste their electrons absorb energy and are excited to higher energy levels. When
reverting (-l:1i!ill<li<i wm) to lower levels, they give out extra energy which appears(~ ~'3ll1) as visible light(~ '5!Wil)
characteristic colours as shown helow: , ! , ...
Ca · Brick red Ba - A
•
i·
L
'
t
l
Chemical properties of alkaline earth metals
<V ~·. Reducing properties: Ox,id~tion ~o~entials: 1!k.aline eart,h met.als have two elect1.'ons in their valenc:·shell. Due to
(bib/large size they are comparatively easily oxidised to M ions. Thus. they are strong reducing agent. On moving down. the
/ -'oxidation potentials increase due lo increase in eleclropositive characlei·. since the strength as a reducing agent increases
.s'-downwj)-rd;:Jrom Be lo Ba. -i rioit~ OJI
~ ¥Aornrntion of oxides re~ d ,) -e: 02- ~ .
; ' (n) Normal oxides: The alkaline earth metals<[;mn. the horH1al dxides of MO type which are obtained y heating'thc
;}' ~ metal in 02 or by their carbonates at high temperature.
_i;.) ~ ~ tJ.
. ~ ~ jJ Ca + 02 ----=---7 Cao
' 9 <' CaCO.i -~ Cao + C02 t ,..
~
1
~ BeO is amphoteric (~'!~) and the oxides of the other metals are basic (~) in character. Their basic character
s ~ ~ increases on moving down the group.
~ l T
~ !~
Question: Why alkali metals are more electropositive than alkaline earth metals? ~ ~
7.. Electrnposhlve character: Although the ionisation energies of these clements are higher than those or alkali
metals. yet (>!l~ <>fl.Ri) it is more easy to make M2' ion of these metals than the alkali metals. These metals. therefore. 'how
strong electropositive character which increases Irom Be to Ba. Sitice these metals have higher ionisation energies than the
alkali metals. these are not strongly electropositive as the alkali metals.
8. e ativities: The values of electrone rativit of these elements arc low r111d decrease from Be to Ba.
ra 11 from Be 1(1 a. owever, both these values or a ares 1g 11 y igner t ant ose o a.
Elements Be Mg ' Ca Sr Ba Ra'
Ionisation energies I I, 900 I g.30 737 I Y·hn 690 I fi·lO 550 I 5•.Yo 502 / 5·20 509
(KJ/mole) (~'Ii') I 12 t757 I 1450 I 1145 I 1065 I 965 I 980
6.
d..
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4. - .···- .. -- - .rJ.... --- .~-...~ -~·- ..
. Example of reaction with nitrogen 6Na+ N ~ 2Na,N
Example of reaction with oxygen
Example of reaction with hydrogen 2Li +H ~ 2LiH Ca + H ~· Call
Example of reaction with halogen
10. Formation of~omplexes: The tendency of M2• ions to fo;111,the complexes decreases with the increases.of the size
of fvt2• ions. lhus sl' ion. on account of its small size, forms fuari~ st~ble, complexes 'such as [BeF.1]'. [BeF4]-, while the
Ba~· fo1111s very few complexes. . . ' ·
Similarities between alkali tind alkdline earth metals . . ,,
The alkali and alkaline earth metals hav~~qulle (~~IC~) { g6od;deal of resemblance (~) in their properties. The
reason for this. is the same outermost energy level invblved for the tai~nc~ electrons. Some similarities between alkali and
alkaline earth metals are given below:
L'.t(fp{_ikc alkali metals.~ are electropositive and have great chemica] a~ti~ity. L- n ~ ,... 1
. -1 · . ,
2. Thcydonotoccurinthcfreestateinthenature. 6h,VJf' .. r,,u,jJ1f...J· .t: t<J<Uj'x-1JfTf~
3. Both are extracted by electrolytic methods from their stable salts such as chlorides. 6 ·
4. Both nrt soft. silvery white in untarnished conditions arid very light. o 1) 1 11-:J' // C@ -i-f:t} D ?
5. React with water to give metal hydroxides and hydrogen gas. Na -1 r1q 0 ~· ('· O " ' 1- .J
6. The hydroxides give strong bases with water. , M
7. They h~ve strong reducing property and formed ionic compounds. ·
8. The react with h dro en, oxv en, halo en. nitre en. acid and formed same com ounds, O'} OX fi
Ionic radii A0
0. 3l 0.65 0. 92 1.1'3..,
Ba··-;-··
ii76.45
1 .3-5- ..
Alkaline earth metal ions Be t a Sr
9. Hydration of hikJ~e earth metals: The cations of alkalind earth metals are extensively ('ilrl~) hydrated to
form the hydrated ions and this Jrocds a-large amount of energy is released which is known as energy of hydration. .
M + x1't20/~ ;tM(Il20)xl + Energy ofhydration
IIydrated cation < / • ·
The values of heats of h dration of M1' ions decrease .with the Increase of ionic radii of M2+ ions.
Ca + 21110 ~ Ca(Oll)i + Oi ·
Cao +H20 ~ Ch(Ollh
.The hc~ts of formation of hydroxides increase from Be(OH)i to Ba(Ol!)2•
I •• ··~~ .
4. F~tt;,~ ar1·alides: the halides of these metals earl be obtained by heating the metals with halogens at ·
appropriate temperature~- by heating the metal carbonates with dilute halogen acid~
Ca + C.12 ~ CaCl2
Ci,,-~t/lf -:J Ctt_Cri.-r~-'1' ·
5. Reaction with acids: Alkaline earth metals react with acids vigorously (~<1<'1!)llA) to form their corresponding
('l~~icf) salts and 112 gas. . JI.... ~ ';
I Ca + 211CI ~ CaCl2 + mr 1..-b. h-"
~ f.t)q 501. CA £c'>v -r,...-L 'i'
6. Formation of h'y:a''rietes: All the clements of alkaline earth metals form the hydrides of MH2 type. BeH2 cannot ht•
prepared by the direct combination or Be and I~. it is prepared by reducing BeCl2 by LiH or LiAIH4•
JJeCl2 + 2LiH c-ihc•· BeHi -+ 2LiCI
Mg, Ca, Sr and Ba form their hydrides when heated wlth H2.
-.. M fM=Mg, Ca, Sr, Bal + H2 ~ MHi
~rmation of carbides: When the elements from Mg to Ba or their oxides are heated with carbon. then-carbides
are obtained. Cat+ 2L · ;
CnO +JC ~ CnC2 + CO ·t
On treatment of carbides of these elements with l~), they liberate (~ ~) acetylene.
CaCz + lH20 ~ Ca(OHh + CH:di
8. Formation of nitrides: All. the clements bum in nitrogen to form nitrides,
, ; 3Ca + N2 ~ Ca-'N2
On treatment or nitrides of these elements with H20. they liberate Ntht ~ : :I . . .
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5. o6 OY. Pharmaceutical uses of Alkaline earth metals
O IA (a) MgO, .
• It is used as antacid .
•:. It is also used in Mg- deficiency(~).
0(j.b)
Mg(Qllh .·
•, In a high dose, it is used as a laxative.
•i Usually used as a non-systemic antacid.i
~ Prnphylactically (cm~ ~l:!<!i) used in strl'ss (~~)induce (~~<>fll1i'l <l>m) ulcer.
. s1m1 antics o e and M2 with ot er a a me eart meta s ··--·
Subject Bervlliumja ••~ ·~·•i.:.I), ·- ~e MJI V..fl'l'f.i.lm~trontium and Barium c~-
Hardsnetais. Be is the hardest - Soft metals, Ba is the softestI. Hardness
2. Melting and boiling points Higflerth'ifo Ca, Sr and Ba. Melting and Lower than Be.and Mg. Melting and
T 11gfpV •!Ph .. li1 h ~ w 1~1'9-. ··' '•' . 'i'.ib
b01 1 oints o , e 111·e.. 2 .est r rz , ·' boiling points of Ba are lowest , ·
3. Colouration to the flame Donot show any colour. ·FiJ· They give characteristic colour to the
-~-l flame Co- Gmtt T(9d iza-~
4. Reaction with hydrogen~1 Do not react '' React with hydrogen to form
/-CJO~ ,.
'
; l hydrides Qi.-rHn - a...u')..
5. Rl'action with drv aili I Do not react React with dry air to form oxides ~· i''
6. Rl'action witf! water(._/ Do not react at ordinary teri1perature bi;i ;..,~ Rea.ct with watefto form hvdr~
7. Solubility of hydroxides in water Insoluble Soluble
R. Nature of hvdroxides fbelo1011/l'~(o!,4, Amphoteric or weakly basic Strongly alkaline 61?-e(2J T'f' ~
9. Precipitation ofcarbonates Tltei1 e11rbo11ates-are not precipitated ~ Thrir carbonat€s are precipitated ffi..
i·n j Ju pn~Mmre of t#I ,, tl'f· tJ JIt,O }I ,,reseAee oF Nll:rGl,f:l)m~Gll - - . "~~»--1' ...... ,.,,.
I 0. Solubility of sulphates in water Soluble ll; ..
'
Insoluble
11. Solubility of sulphidl's in water Soluble and are not hydrolysed. Soluble and arc hydroly~ed
'
in Ite 0 OWlnJ.! ta e: 11.:··
Subiect i Alkaline earth metals. .-. Alkali metals
I.Hardness f 5o++na.JY} More harder ,.J'·,Q.aj0Q-J167. Less harder M.er"'· · .~M:Jr.
2. Heaviness More heavier "": .... Less heavier
3. Meltinz points f@)o1LM.7 More than alkali metals Lower than.alkaline earth metals
4. Basic character Ll.-;s basic More basic
5. Size Smaller than alkali metals Larger than alkaline earth metals
6. Pollrtsinz capacity Greater than alkali metals Lower than alkaline earth metals
1.-0xides and hvdroxides More covalent in character Less covalent in character
8. Reaction with 'atefat9 ~l" .refvf!'> Ca, Sr, Ba react less Vigorously All metals react moreviaorouslv
9.$otubility in water
~
Carbonates, sulphonates and phosphates All metals are soluble ··-
. /[)e-rvtrf f~ afi insoluble 0 r~ . ·pc)
• U/YXJI._.
-
IO...Reducing nronertv Lower than alkali metals Higher than alkaline earth metals
,p~~P·. -p(')~~-i" 'hJ (4( '(J,;.} . ~
imilarities of Be and Mg with other alkaline earth metals · >'· ;1~ DB~Al ~~ @hJJxffC'd
I. Both Be. Mg and Ca, Sr. Sa h~ve two electrons in their oufennost shells. ~ . oG-t-h "~ 1..J
2. The valency ?fboth elements' is two... @ 'Bodh pa.nhci'po.fQ~ r'n. polwu'oa...fo:rrL
-: 3. Both react with halogens to form halides.: . . . . _ . Q 6 howD. e.tuf.,..,.· cc.1,,l c.oii.d..ud-tv•'~~·
k -1..Xn' ~h_Jli( + Glz ) 2tl€1t; Mg+ Cl1 ·".7 MgCli; Ca"+-:.c!i ~ CaCl2 . · U
/ 4. Both combine directly wit.h nitrogen to funtfnit.ilfl~~; '<1'J)~~l!li::1-:/ '' ·c 9 's'· i, _ ;., ~..,,,,.
! . •.·.·. '·'' , r-, ..!::'.':) rww•.. uuc.nC.
e.e... ff"l- ~- N't {• Hii~ 3M~ +, "'l ',. ~bN2; ~.ca + Ni ~ C!l,1N2 ' -
S. Both react with dilute acids toforrn hydrogen. ·. · ·· ,., ' ., · •· . 'Prn>fleiJ(j
I -+ LiElz-~ Mg + HlCI ~ MgCl2 + lt2: Ca + UICI -4 CaC'2 + H2 @ Ve~pot?r1·.J-r'01>-
e,.e.. + '2.loc.A... • r::rrrop-e.<.J--v. •
f B h lk I' h .....J
1
i« J:.h.Q =>! ~ ::fov'cJ·!J l)ueA ar. - w~r ~ f>flh,Je~Jeol :Jr, ~ ·~ j- ~13~
(fn1 /.)LUQc{V ajJP)/ aor'ti,q ,11 dho ~e,J-,. ¥1 /::e,''llfl c}J,t'~.®.Ji•on_1•.J. l} j ( ,
. / . i U . 0. _ , WOl.V-(7 fl~JI ,r.:Jo :l;/u_bltlcc:) ruvJ.
.::r~c ,..JJerJI') . To ruiJ.u.cQ ::t"'-t>e .::1o~c. t.~f!I> Afj2.G1309, o ,,/) ~ Q.QI dJt:/-.-' , -.1- M"1 s ..i....
- ~Pf. ' , ..i()')C.I c ~1:71Q • 'uz 130.t.? V•[._ 0
.
711:..P. oj.~lc~'f (Je !!p:rt#-i'l'U. Nwi1C} )tllJrd.-M-M·cAlixo 9J- ho.o ~ .Jhf la-r,w. /ivl?. Pr<()~~ · So, "1.J.)S130J'2 t-hiC> ~aulQ a.braaitlo ::
;PMPlof(t,11'·"'1 'j)c11ChtLe ,'n :flu_ Mo"M.th CJ4tr;). woM 0><'Col1.Q.h, 1'.J- LoJid-J.., dJ.u ~oJ, Ti wr'/I rud.uce .J~ ~·c ellecJ b
. _JW-~-e··11 o rw;!_ 9. The electroposltlve nature C;>:!Jlinuously increases from Be to Ra in the seconc! group. as in the first group from Li
! L.-fi. to Cs. : ) .r .-.1) c: ) ....@;j ' I
l . - 2 ~; { 2:z:i{ ~J-1.J ;.b<nr i() r-"1@1 1Sry0 ~°62 ccr' j I te <f"O 0 V~ ~ - 'K....etdvu ch(
1 m · · · · · . €'1··. 1(7jj; · · 1,~··'-..... 1 • r
o:?Contrasts I Dissi'fuilarities I Differences between alkruinc eartlf'and alkallse metals b 1" ~ 9 ~o
The points of the contrast between alkaline earth arid alkali metals arisemainly due to the presence of two valence
electrons in the case of alkali he earth metals and one valence electron in the case of alkali metals. The differences are given
. I f II ·'· bl
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6. ' l
.- ! _ ......--.---------·
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 (C"lriJn]fU)
abundantly ("f~"f~) in nature. ·· ·
These configurations show that all the halogens have seven electrons (ns2np5) in llteir outermost shell. Since the
additional electn~n in these clements enters the p-orhital of the outermost shell, these are called p-block elements or the long
form of the pcriPdic table. · ;'
Elements Atoinic number Electronic confi uration Valence shell electronicconfiguration
F 9 Is 2s2p- 2s· 2p·
Cl 17 I s2 2s2 2p6 3s2 3p5 3s1 3p~
Br 35 I s2 2s2 2p6 3s2 3p6 3d10 4s2 4p~ . . 4s1 4p~
I 53 ls2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5S2 5p5 5s1 Sp~
At 85 ls2 2s2 2 6
3s2 3 "3d'° 4s2 4 6
4d'° 4f1~ 5s2 5 6s1 6 5
·~·
Y:llsed lo prepare soap suspending nnd emulsifying :tg~1tt.
<D Magnesium tri silicate
• It is used as an ni~tacid to neutralize excess amount of HCI into stomach.
/11 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 inproducing of chocolate. · '
~ 7 - 8. 5% Mg(OHh in water is called milk of magnesia. It is used as laxative.
---(tj' MgSO~ '.is used as laxative.' ·
(f) MgC0.1 ,
• It is used as an a~itacid and mild laxative (9frn'$'11~<l'iCTI1!1~.
• . 11 is also used ns food additive ("?!!!!~)iii tooth aiid fare powder,
(g) CaCl2 · U!Jf· . . . . . .. ., . ~ ~l'9.~:ic ,~ tO~ I. v c1,c'lf1 x
...,,,.--s~ 10% s~1lut1oi~ of .encl~ 1s used m tetnnl disease .. (_ ~b!vo(j oj G.£2i 1 n blood,; . · .
/'".' It 1s used for mamtammg the proper heartbeat. t.v. h_,,,, 'H'h!Ut '-- _ t : + '. 2 -·~- . 1. .I) ,.,.,.,__ .b. _1
. . ' . 7" I ·-uv.>-W' CO·,,,..,oc t Ot> 0 J~07' I '-"'-"U-bU'GI I
(h) Calcium . . · . .. . I ,,
· ~ is the principle cation of the bohe hian'ow.(Fof h'eatment the osteoporosis (f'ii <l'WI $. ~ m l0'3m)
and rickets ('P111 ~ ~ W ~ -a ~ W zj'3m) calcium phos ·hate is used.
7~
~ . /iJ h /I)
/' Us~ntid0tf{f<l:3! ~ Ul1'11 ~lf<ll ~~-i t>f M~giieslbin. . · · ce co .C'.'
(i) csso, f/fJ{.:}.,~ ~ ..fM.,ac/lve /'7'1.....!Jl1~c/.J~ ...,.,, ~ ~ ~ ~"o.Jna ,'()
/-It is used as diluent {i!l~~'lll?t<ll) in tablet. ,, ~ • 7...J 1.~ tJMd ::fa ~~;.., tMctpf>• cVr!d.. ct
___-- ( lscd as plaster clust in plaster of broken bone. CCt! 5CJti ; 2 tf12_ o ~ ::fo 1'<r1:Lttit'e =» TM ;a}tb:/.
~adi11111 snits are used in cancer therapy. · / ·
ik-(ncryllium is used as transparent in X - ray. ~ . ·, .
/ · ~ - ~ m :;i +o-a1t1.c-~ ".W! '? - .Ll'91':;!- rTV cqvp ['{
Question: How Mg(OH)2 acts as suspending and emulsifying agent?
Solution: Mg(Ol-l), combines with other ingredients oLa solution to form complex. This complex remains suspend
(~)in suspensionand together in emulsion, These way Mg{Ofth acts as suspending arid emulsifying agent. ·
~~ fou _ch~_,·. - ,·j r'f> ~nQJ~ablQ r-tji~D!l_· c!rn~~''g_-' QJ<1l : b~:aLoHr~~ ,·'Nln_t .~ ha.1°e.TL~
~ ei.Ja , / e 1"= ,~ ; ~ o ph"""".'~~call~ '.(;"''"", (1'<n~t3'. J) .s Jcm · d lu •t/ ~ U~9" ,.b "" P":l
304 -tg ~ c/.JJv.brJ-·6 ·1lalogens '-f ff.>,~fun~t!~~.mi·~.e.~ 1J_ ~?-~aJ-r(Q p'(.10
to ~ Questllm~hat are halogens and wl~y a.re they so c~lled! bwl~ &so,. 1 I> ~·0~9-{~.}. '~ .~o ~>..J.hciJ.,..,i ,J
lntroductlon: Group VIIA of the periodic table consists of five clements which.are Fluorine (I·). Chlorine ((I), Bromine _.J
(B~). lodi1.1c (_I)' and Astatine (At).,.ifhe elen.~~s F. Cl. 81: ai1(~ I iil·e collectively di led Halogens. (('stn!ine i.la1; Eli.!ieFlwr~d iu 'YY'tD rrJ.. p
l~fl unff..1s an unstable element ol"ra ioacuve Oi1gi . . . . Dg<1HI "-......_ · . --{"'hC'J...n
The term hal~ge_n is derived from the Greek lrnl.os (=salt) and ge~es (=. born) meaning sal produc.ers because most. o'.~
these elements exist 111 seawater. notably(~~) 111 the form of their sodium compounds. Thus ~1e~;e eleme11ti; are ·.:alv
Haloge!h . "' N Cf. c..l ·' ,
~onic confi ufation: The electronic confi zuration of the atoms of halo ens are riven below:
Qg_ '. @)1 :J; 1'~ er ~r'rn~1 p /.Q_ c..aJ1·r:rn oJ-> ::.,'tu bano ThAJ~"m-e
!
Md.
Imran
Nur
Manik
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