1. The document discusses several physical and chemical properties of alkali metals including their electronic configurations, atomic and ionic radii, ionization energies, oxidation states, and reactions with oxygen and water. 2. Alkali metals have low ionization energies due to their single outer electron being weakly bound. Their reactivity increases down the group as it becomes easier to remove this electron. 3. They react rapidly with oxygen and air to form oxides, with the smaller alkali metals like lithium forming monoxides and the larger ones forming superoxides. They are stored in oil to prevent reaction with air.

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

2. '
! liT1G'l't "f1
I
______ ,__
_ ......_,,__,__ ,,_~··-
...•.,
--·---,..-·--·---.--:
BoilitP (lint "C) 1330 l!)?;b ~ 98'0 760 (iB.~--~ 670 ------
6. Heats of atomization: /lkali metals have low heats of atomization which indicates that there arc weak interatomic
bonds in alkali metals.
Ionic radii A") 0.60 0.95 1.33 -:48 1.6 '
1
' ' 2~ J.. Oens;!Y' Th< densi I;" o 1:alkaI; "'''"'~ are q~;,, Iow due lo th'. I,..g.e '"''.";' '"'""'": U, Na and K '"~ I;gluer Iha"
..V> water. Ihe densities mcrcasc with the increase 111 atonuc number from l.i to Cs. K ts however. lighter than Na which 1s,due lo
@' an unusual inc:1icase in atoniic size of K. :>n_?-sNJ,t 0 e- <('Q>CIL ®{-.:i ClJ'210l<r~..-;-::i ~1 0-< ~t e"'J '2f1Gq -Tl' •
l .€9 Elements i Li Na K Rb Cs
.~ {?::6' Densit ( 1/c.c): ~ O·:J2 0.9711 0.8'$ 1.525 . 1.903
5. Me1td1g 1111d boiling points: The melting and boiling points of alkali metals are very low because of the presence
of weak interaiomic bonds in the solid state of the alkali metals. These bonds are due lei their atomic radii and mainly due lo
their 'electronic configuration. As the size of the metal atoms increases. the repulsion of the non-bonding electron also
increases. Jhis increases in the repulsion of ~e non-b<mding electron decreases the melting and boiling points of alkali
inetals · n V 111 · · m Li t() Cs. ---- -
El<'ments Li Na K Rb /
18.5 . tt66 97.8 ~ 6Q. 3 38.9
Atomic radii t A" 1.5 i:;:W l.· 9 G
Atomic volume (c.c.) 12.97 23.6)(
. '
These eonfigurati~~ show that the outermost shell' of thes~ elements have one s electron (s1 electron) while the
penultimate (~"1C'H~ ~~fi1) shell contain eight electrons (ns~np11) except Lithium. When this valence shell electron is
lost. the alkali metals are converted into M' ions which have inert gas configuration. Since the additional electron enter' us
orbital these arcs-block clements. ·
It is due to the similarity in the electronic configuration of the alkali metals. tliey: have similar physical.and chemical
properties ' . ~
Physical prope~ties of al~~li metal~ . : .- , . · (~ ~ ;J(l,;:i .,rle> '.
- Some of the physical properties of alkali metals are d1scusseJb,tlow: . • ?1'~ <fl1( ,
~ ~Physical state: With the exception of Li. the alkali metals are extremely soft and readily fused. They are highly
malleable(~~·~~ ~'llJ) arid ductile (tfN'l rr'l1 ~ ~ <!17frl). When freshly cut. they have a bright ~ (~i)
which is quickly tarnished(~ '!!:'3m) as~ootf'as rhetal comes in contact with atmosphere. ~e....--
~.ntomic number and'Atomic wei ht: When·~~ fucecd Gf;'ot"ti~a~~~number and atomic f wei 1ht will increase.
Ekments U Na K Rb Cs f-rl
Atomic number 3 ·II 19-; 37 55 '61
Elements Atoinlc no Valcm:c shell electronic wnfigtfri11t1·1n
Li 3 2s
Na 11 Js'
K 19 4s1
Rh 37 5s1
Cs 55 6s1
Fr 87
6
7s1 7s1
q, K"" Introduction: The elements Lithium (Li), Sodium (Na), Potassium (K), Ru idium (Rb), aesium (Cs) and Francium
~I). (Fr) constitute group 1 A of the periodic table. These elements are known as alkali etas. sine they form strongly alkaline
oxides and hydroxides. In the periodic table they occupy (~tc'I ~1) a position just after the members of zero group. __
Electronic configuration
The electronic confi ruration ofthe atoms of alkali metals are riven In the followin 1 table:
•
Alkali Metals
0 c c.{)Ji·~ · =ns«.en
/ 72 71al-vl (_f.
x~
Atomicweight 6.94 ~ 2'!2•99 /~0·01 132.9 r@:IJocicfr'...;Q_22
. Jo p :l-o looi~oYI'; 1'.e'
J. Atomic volume, atomic and ionic radii: As we move from Li to Cs, an extra shell of electrons is added lo each
clement. The addition of an ex Ira shell increases the atomic voluri1~. Therefore, we find that, there is an increase of nionuc
and ionic radii as we mo from l.i to Cs. - ---t
Elements ,i NaMd.
Imran
Nur
Manik
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3. ,I,- --- -·--·,-·-~--~~Hi U:-"'?4-it. YN4Wt4!W MQI _ u•~--.....,._...,.,..,....,.~·•··
~-·
Thus we seca that the alkali metals can lose only one electron and hence show only+ I oxidation state. It is evident(~)
from the configuration of M' catili'ns given above that these cations have no unpaired electrons and hence arc diamauncric
and colourless. ;All the compounds of alkali metals are colourless with the exception pf those in which the anions arc
coloured. as tor example: permanganates and dichromates.
/ 14. Distortion I Polarising power of alkali metal cations: When alkali metal cations approach (~ ~-.smi near an
anion. the cation attracts the outermost electrons of the anion and repels (~01 <!Im) the nu1c'leus. Thus the distortion (~)or
polarization of t'hc anion takes place.This distortion results in the sharing of electrons between two oppositely charged _ions
and the bond between the cation and anion becomes partly covalent (~) in character. Jn general the smaller cations
polarise the anions more effectively than bigger ones. Therefore. the lithium salts are slightly covalent while other alkali
metal salts arc ionic.
its nearest noorcgas wmc 11s very sta e.
Atom (M) M• cation
Li 2.1 Li' -2orfHe] ... ~
Na - 2.8,1 !i Na - 2,8or [Ne]
K 2.8.8.1 K' -2.8.8 or fArl
,/1 I. Electrical conductivitv: The individual atoms in the crystal structure of the metals arc held together by the valence
~ct1:ons. In alkali metals. this binding is relatively weak, since the valance electrons arc loosely held. These loosely held
o ~ ' electrons arc. therefore, free to move throughout the metal structure with the result that the alkali metals -havc high
0 conductivity. . .
c/ 12. Coluration to the flame: We have seen that the outer electron of the atom of alkali metals is loosely held with the
'nucleus and hence it can he easily excited to the higher energy levels even by a small amount of heat energy. During the
O ~ excitation process the electron ahsorbs some energy and when tl;U~ excited electron comes back to its original position. it
D gives out absorbed energy in the form of light in visible region of the electromagnetic spectrum (<iofffel) and hence(.!!~ <lll?IT."f,
~) the colour isimparted (~ ~81Tl) by the atom to the flame. Since(~.~~) the a;riount of energy absorbed du.ring
the excitation process is different in different atoms, different colours are imparted hy the atoms to the flame.
Example: l.i Crimson red. N<1 · Golden yellow. K. Rb and Cs -- Violet
Question:
~ IJ. Oxidation states: We know that alkali ;netals can lose their ns electron quite easily to form the unipositivc ion
o,I ~ . M'.. The lose of second electron from M' cation to form ~cation is very difficult. since M+ cation has the configuration of
~ l bl 1 ·I . hi
Electronc ativitv 1.0 0. 9 0.8 0.8 0.7
Elements Li . Na K Rb Cs
~ ~) . .
?l 9. Elrctrnpositi'e_l Metalliccharacter: The clem~nts which have a stro'.1g ten~iency to lose their outermost rlectrPns lo
<)ty ftmn the c;it1'.111s arc said to he ~lcctropos1t1ve or metallic elements '. In case of alkali metals we have see1: that ns electron 111
°D these metals 1s weakly pound with the nucleus and hence can he easily removed from the atom to form M cation.
M ___., M' + e
Thus. these metals have a strong tendency to lose their nsl electron to form M' cation and hence show strong
electropoxitive or metallic character." Because of the successive (;n;m'1'5) increase in the distance or m..1 electron [rom the·
nucleus on proceeding from Li to Cs. the tendency of the atoms to lose ns1 electron goes on increasing from Li to Cs. lhus
the clcctropositive chnracter of alkali metals increases from l.i to Cs.
· "> /fO. Electronegatlvlty: Alkali metals have low values of clectronegativity, that is. they have little tendency touuract
lB~efectrons towards themselves. Their clcctropositive character increases from Li to Cs and their electronegative character
decreases in the same order. '
375.7Ionization ener tics 520.3 495.8 418.9 403
CsElements Li Na K Rb
0""'
.ft:' 7. Photo clectrlc effect I Effect or light: The ni electron in the atoms of alkali metals is so loosely held with the 1111ckl1-i
n-~/ that even the low energy photons can eject this Ms1 electron from the surfnce of these metals. This property ol' emitting thc~to
{{!;, / be used in photo electric cells which are sensitive"'to blue light. ,,,,,51 eh.~--rrcm
8. Ionization energies: We know that alkali metals have only one electron in theiroutermost shell, This ns electron is so
weakly held with the nucleus that it can be removed very easily. So ionization energies of alkali metals arc very low. As the
distance of ns1 electron from the nucleus increases 011 moving from Li to Cs. its removal becomes more and more easy as we
roceed from Li to Cs. Thus. the ionization ener ies of alkali metals o on decreasing as shown below:
LI Na K 0 li-:.:.:.:..:.::.:.:.:..::.::____ __....;.-+-~l~.7-4----------4-~l.~24---------+~,~.0-3-------+--+-'~.-9-8--------~0.-9-() =l1....-.~~---~~~-'-~~~-~~---1_.:.;~~~~~~-'-.;;..;..:.-'--~~~-"--l-->'1(1"
Md.
Imran
Nur
Manik
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4. . '
i, ; . .. ~·JIcni'dJJ>.. ' .
~. Formation of hydroxides: Hydroxides of alkali metals"c~n be prepared by treating the normal oxides or metals with
11.t_>. . Li1-0 -t-li!tlO ~ tli'oH
. Na20 + H20 ~ 2NaOH·T-fi'v
l 2Li + 21-120 ~ 2LfOH + H2 • r
Since the alkali metals are highly electropositive, there hydroxid~s are the strongest bases. Since the clectropo-iuvc
character of the metals increases from Li to Cs. the basic character of their hydroxides increases from LiOfl to CsOH.
hydroxides are stable towards heal and their thermal Stability increases from LiOH to CsOH. liM . -fV¬ fft.--'
·, . . j ,9)1~''j IY)__p}WUJI/ ()-n
rmation of hydrides I Reaction with H2: The alkali metals, on heating.fuct~h hydrogen lo give crystalline
e ydrides, Since the elcctropositive character of alkali metals increases from Li to Cs. thus reaction with hydrogen
decreases from Li to Cs.
f
lt
[
Question: Explain that. Super (~xides of alkali metals arc paramagnetic and coloured ;,
A11s11·<·r: Alkali metals react with oxygen or air rapidly and form different types of oxides such as monoxide. peroxide.
super oxide. Li when burnt in O! gives lithium monoxide. ,
K, Rb and Cs react 'with 01to form super oxide. ()
K + CJ2 --4 Kd2 . . -
The super oxide ion has a three electron bond as shown below: ~ •• .!.... 2!)
The presence of orit unpaired electron in it makes this ion paramagnetic andcoloured.
~
I
------~~ I
.Ouestion : Why alkali metals store in kerosene or paraffin oil?
/ .S. Formation of oxides (Reaction with 0 or air): Alkali metals react with 02 or air rapidly and thus get tarnished
(fop>~ ~-.i.lm) due to the formation of their oxide on the surface of the metals. For this reason alkali metals are stored in
kerosene or paraffin oil.
Li when burnt in 02 gives mainly lithium monoxide or normal oxide(Li-O)
. 4Li + 02 -~ 2Li20
Na when burnt in 02 gives sodium peroxide (Na202)
' 2Na + 02 ~ Na202 IAnswer <fl~ ~I
Other alkali metals react with ()i9 form super oxide of MO~ type.
M (M"=K, Rb, Cs)+ 02 ~ M02
Gm tA e1Q.; rnuv1D oss: 11-e~ "JWo..Q.:Ir · • -e 'ot:.>e11l!X <..1! ..., t NI-
. · pec,I~ .
. vfhc..nu. . .i:f. s ?f ~~ ' . / ef) . a, ..
;f0_Ueact~,·1t. ~he .first 10111zat1~n energies ~nd electrone~at~-t~~s of alkali r.11etals arc .the lowest ?fall the ~lements and
(9~ tl~e1r heats of aton~1zat1on arc rr_lat1vrly low. Th~se pro~~~ 1~1a.~e .the alkali mdal.s, lughly reactive ~sp~rntlly towards
highly electronegative elements CI and O with which they ~10111c con11)ouuds. The react 1 vily of these mernls increases wilh
the increase of their atomic number. 51'nee :!how te Q ~ d.o.e~ r'n. ;:/-ha r·f· .
Example: Li reacts slowlv 11,0: Na reacts vigorouslv <~): K, Rh a11d Cs.,,_reacls with Increasing violence
_ ' . 0 -..:.~')1.QtJ 11 Ct 'fl-!J Cl.iJ-eHlf ·- r::JJ)'ft.~)1)
(~li~~). ~:t;..(j (oXJ(J.t'r.n'"j~-ci-ctepj-vr),- -r1.IJJJ~ctrm.
~Reducii1~ property: A reducing agent is a substances which can loss electrons, Alkali metals have a strong tendency
to lose their ns'clectron, thus they act as strong reducing agent. ··
llw tendency of alkali metals t() act flS strong reducing agents is evident ('f""!E) from the fact that these metals can
liberate (~'Rt) II from H ,()and acids. t ~ rid-r® v<:!l-w&.1 -)zeno
2~1°+ 21fiU ~ 2M.,.OH + H~,_. -:.,; _ ,
2M0+ 21tc1----'> 21fb + m'1' ~ CooTttt(.,- H2 (<tfl -e- ~ofsL ~Cf... (:'.5--J ~u~
, voJ.a,,~ct> "Z~10~-t-i _ .,,0cV;liJ1L.ru·~
·. 9,~ . ..--::::: 3. Formation of ionic compounds: Alkali metals are highly electropositive. Thus they reactrwith rfrccti·onegntivc
~~ ~ornpoun such as halogen to form ioniccompounds. The formation of ionic compound increases on going from Li lo Cs.
"'" ~"2. t-Po-m-j(n aj JM.Vims' er 2 Na+ Cl2...~ 2 NaCl , ,,/ J.J ,,., ., cJ.;Lo.Jed et7Y'el rb ·
'V MtP e.x-l:em/b1"~__.) r '=i .
4. Hydration of alkali metals ion: Alkali metals ionhenct with water and form hydrated cation. The hydration
process of alkali metals ion is allrxothermic process. It is depend oil the size of alkali metals ion. Hydration property
increases with the decrease of the size of ion.
Nat+ 112(> ~ 1Na(H20)1'
r~..,....~-~ , ~- ._...,....-~--.. ~.--_~.,... ... _ -
'.J?'/{'J/.POMd pcvdi'CJ'f)o_.j,~ of• Q..(l ~ r'n j-~ 71..tta.Cd-ro?fl 1'nd.J'~I) 1°{1) 1'.nrneae;,ed JUJLe:f:r'}f'!)
Nr.nma.l €~(') cwnn'i. r;,how h.fLO_Cfr'.,,t'N. 'Ra_ac J,1'11°-t:J ,5 f.)nown vy ffi9_. 1'o"Du'reJ ~ ..,.Ji
·u ""~~
_50, whivn._ -d·J.& T•fl 11'n.CT/.P.o{eP/) )Woc/-r"r'f_5j diLcllSJ.Of..P/; !).l"d -nr e ve'l•f>a • ~'7
1
,_;)e,J
j._O
Md.
Imran
Nur
Manik
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5. ~·r./
'-· .-:·""'l¥"~~··..-••-"t':'.-:"::!!~~----·:'"'";~·,~ • '·c· --·····- __ , ._ ----· _L_
Pharmaceutical uses of alkali metals _.,,,
I. LiCI is used to control the air conditioning arrangement or humidity(~) of air in the whole room.
2. LillCO_, is used as removing agent in Gout(~) disease.
J. Na and k
(a) Na' Ion is the principle cati;n of extracellular fluid. Hyponatremia disease is caused by the lack of Na'
inextracel lular fluid. This disease damages our lmmutte (~) system and affects our body. .
(h) re: ion is the principle cation of intracellular fluid. The lack of K• in intracellular fluid causes
Hypnkalemia. To protect this disease KCI is given in the body: . · '
(c) Na and K are associated with nerve impulse (~9Mt) and con(ruction and relaxation mechanism or
the heart. '
(d) For adjusting tonicity Na and Kare used.
4. NaCl and KCi
(a) Hypertonic solution of NaCl is used to prevent the coronial edema (~ c<lir-1 1"141'(1"1 ~ ~ ~
!ti'! ~~disease of the eye. . . .. . . . . .·
(b) Isotonic solution of NaCl is used cis irrigation(~~~~~~ 'Rt) agent.
(c) 6% Solution of NaCl is used as prese~>ative ('!(fu a<n).
(d) NaCl altd KCI arc the major component of otal dehydtation saliue.
(e) KCI is used as Diuretics. ·
5. NaHCO_, is used:
(a) as antacid which neutralizes the acidity in the stomach.
(h) In the body as buffering agent. . -,
(c) as the major component of oral dehydration saline.
(d) in the preparation of effervescent(~) agent.
(e) in the treatment <;>fCH,OH poisoning.
(f) as barking powder.
6. NaCN is used as insecticide (Mi~""'l~'--'l....l"R!'""') or germicide (~<llfll"R! 9f'11'1f) in agriculture for pest control.
.7. Na-CMC (Sodium carboxy methyl cellulose) is used as suspending agent in the preparation of suspension.
8. Kl is used as:
(a) Hypothyroidism (VJl'a:ilC4JCl!Hl "1~'15SIC<t •<rt 'RI) to increase the secretion (~Cf) of thyroid gland.
(b) In goiter(~) disease as removing agent.
1·-1
t"
r-
lI
!..!
. Formation of halides: Action of halogens: Alkali metals combine directly with halogens to form halides. /s the
cctroposilive character increases from Li to Cs. the formation of alkali halides increases rn1111 Li lo Cs .
., . . 2Na +Ii --7 2Nal
~ ~~o•iof liquid ammonia: The al bli metab dissol >< in Iiquid amnion ia wit hout the evolution (~<"lfu) of hyd mge:•
· gas and make, a solution. These solutions arc good reducing agents. ·fl)cir reducing property is due to the presence '(lr lrcc
a111111011iated clectrens. Thus these solutions
a. reduce metal halides to free metals.
b. remo1>e hydrogen atoms from acetylenic hydrocarbons.
i CH1:=CH + e '-)CH1:=C + ~
c, rcnw~-c halogen atoms from organic molecules.
j C2H~CI + ze· --7 C211~- + ct· v.
. Formation of amnlgarns: Action of mercury: Alkali 1111:1als dissolve readily in niorcury and limn the umnlgams. lhis
. ·z·l'OCC ·;is V<'r)' exothermic.
· · ·.· Na+llg -7Na-llg /111=-,·e
. React" ,~·ith dilute acids: The alkali metals react violently with dilute acids and liberate hydrogen gas. cm jlJiWj r1-(l·~ ""ei d:
/ . 2Na + ZllCI --7 2NaCI + 112 I .
1
.» eactlon with Nitrogen: lhe alkali metals form nitrides when gently heated in presence of nitrogen.
/ · 6Nit + N2 --7 2Na,N
The nitrides are readil'y decomposed In presence of waler giving of Nil,.
Na.1N + 31120 -43NaOH +NH_, T
Md.
Imran
Nur
Manik
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