Chemistry of alkali and alkaline earth metals and halogen compounds including their Pharmaceutical applications.

1. Alkali Metals: Group I
Md. Imran Nur Manik
Lecturer, NUB

2. Alkali Metals
Electron structure and reactivity
Physical properties
Summary activities
Reactions
Uses
Contents

3. H
Rn
Xe
Kr
Ar
Ne
Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? ? ? ? ? ? ?
Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At
Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I
Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br
Mg Al Si P S Cl
Be B C N O F
Cs
Rb
K
Na
Li
Fr
Group 1A – the alkali metals
Except hydrogen the elements of group 1A of the periodic
table form alkali solutions by reacting with water. These
elements are called alkali metals.1
He
Cs
Rb
K
Na
Li
Fr
Of these alkali metals, francium
(Fr) is a very rare, radioactive
and unstable element. This
makes it difficult to study.

4. Electron structure
All alkali metals have 1 electron in their outer shell.
lithium
2,1
sodium
2,8,1
potassium
2,8,8,1
 They can easily obtain the
stable configuration of an inert
gas by losing 1 electron
 They have similar physical and
chemical properties
 They all lose their outer shell
electron in reactions to form
positive ions with a +1 charge
This means that:

5. Electron structure and reactivity
The reactivity of alkali metals increases down the group.
What is the reason for this?
Cs
Rb
K
Na
Li
increaseinreactivity
 The size of each element’s atoms, and the
number of full electron shells, increases down
the group.
 This means that, down the group, the electron
in the outer shell gets further away from the
nucleus and is shielded by more electron shells.
 The further an electron is from the positive
attraction of the nucleus, the easier it can be
lost in reactions.
 This means that reactivity increases as the size
of the atom increases.

6. Physical properties
Alkali metals are different to typical (transition) metals, such
as iron and copper. Unlike typical metals, alkali metals:
 they are shiny – this is only seen when
they are freshly cut.
 they are good conductors of heat and
electricity;
 are soft and can be cut by a knife – softness increases
down the group;
 have a low density –lithium, sodium and potassium float
on water.
 have low melting and boiling points
However, alkali metals do share a few
properties with typical metals, because:

7. 1. Nature: all of them are metals
2. Colour: like white silver.
3. Physical state: except Li, they are extremely soft and
highly malleable and ductile.
4. Atomic volume, Atomic and ionic radii: increases
from Li to Cs. Due to the addition of an extra shell of
electrons to each element.
Elements
Li Na K Rb Cs Fr
Atomic
volume
(c.c.)
12.97 23.68 45.36 55.80 69.95
Atomic
radii (Aº)
1.5 1.86 2.27 2.43 2.62 2.7
Ionic
radii
(Aº)
0.6 0.96 1.33 1.48 1.69 -

8. 5. Ionization potential: Have low ionisation
potential. The ns1 electron is so weakly held with
the nucleus that it can be removed very easily.
decreases from Li to Cs.
6. Electronegativity: Alkali metals have a strong
tendency to lose their ns1 electron and hence
have electropositive character. Because of this
electropositive character, these metals have very
little electronegative character.
Elements Li Na K Rb Cs
Electronegativity 1.0 0.9 0.8 0.8 0.7

9. 7. Melting and boiling point
The melting and boiling point of alkali metals decreases down
the group.
Melting points are lower than for typical (transition) metals,
because of the presence of weak interatomic bonds in the
solid state of alkali metals.
lithium
potassium
sodium
rubidium
caesium
181
98
64
39
28

10. 8. Density
The alkali metals generally become more dense down the
group, due to the large atomic volumes; but the trend is not
perfect because potassium is less dense than sodium due
to an unusual increase in atomic size of K.
Water has a density of 1g/dm3. Lithium, sodium and
potassium are all less dense than water and so will float.
Element Density (g/dm3)
lithium
potassium
sodium
rubidium
caesium
0.53
0.97
0.86
1.53
1.87

11. 9. Electropositive character:
M → M+ + e-
increases from Li to Cs.
10. Reducing properties:
Reducing agent is a substance which can lose
electrons. Since the alkali metals have a strong tendency to
lose their outermost electrons, they act as good reducing
agents.
2M + 2HCl → 2MCl + H2
11. Colouration to the flame:
Li → Crimson red;
Na → Golden yellow;
K → Violet;
Rb → Lilac red;
Cs → Bright blue.
This property is used to detect their presence in salt by a
test known as flame test.
12. Conductivity: good conductors of heat and electricity.

12. Chemicalproperties
1. Reaction with H2:
Alkali metals combine directly with hydrogen on
gentle heating and form crystalline
colourless compound known as metal
hydrides. These ionic compounds are
composed of alkali metal positive ion (M+)
and negative hydride ion (H-).
2M + H2 = 2MH
2Na + H2 = 2NaH
These hydrides are easily decomposed by
water producing hydrogen.
MH + H2O = MOH + H2
NaH + H2O = NaOH +H2

13. 2. Reactions with oxygen
All alkali metals react with O2 or air
rapidly to form metal oxides. This
produces a layer of dull oxide on the
surface of the metal and get tarnished.
The speed with which alkali metals react
with air increases down the group:
Why are alkali metals stored in oil?
 lithium – tarnishes slowly;
 sodium – tarnishes quickly;
 potassium – tarnishes very quickly.
The oil prevents them from reacting with air and tarnishing.

14. 4Li(s) + O2(g)  2Li2O(s)
The reaction between an alkali metal and air is an example
of an oxidation reaction:
lithium + oxygen  lithium monoxide
2Na(s) + O2(g)  Na2O2 (s)
sodium + oxygen  sodium peroxide
Other alkali metals react with O2 to form super oxide.
M + O2 → MO2 (M = K, Rb, Cs)

15. 3. Reaction with water

16. All alkali metals react readily with water. The reaction
becomes more vigorous down the group, and creates a lot
of heat.
The reaction also produces a gas that can be ignited by a
lighted splint. What is this gas?
Li Li
O
H H
O
H H O H
-
O H
-
H H
Li +
Li +
This reaction creates alkaline hydroxide ions. This is why
the group 1 elements are called the alkali metals.
+ + +

17. 2Li(s) + 2H2O(l)  2LiOH(aq) + H2 (g)
Lithium is the least reactive of the alkali metals. When
added to water, it fizzes and moves around slowly across
the surface of the water.
lithium + water  lithium + hydrogen
hydroxide

18. 2Na(s) + 2H2O(l)  2NaOH(aq) + H2 (g)
When added to water, sodium fizzes
more than lithium, and moves
quickly across the surface of the
water. The sodium melts as it reacts,
and it becomes spherical and shiny,
like a ball bearing. The hydrogen
sometimes catches fire because of
the heat from the reaction.
sodium + water  sodium + hydrogen
hydroxide

19. When added to water,
potassium burns with a lilac
flame and the hydrogen
catches fire immediately. The
potassium moves across the
surface of the water very
quickly. Like sodium, it melts
with the heat of the reaction.
2K(s) + 2H2O(l)  2KOH(aq) + H2 (g)
potassium + water  potassium + hydrogen
hydroxide

20. All alkali metals react violently when heated with halogens
to form alkali halides. For example,
4. Reaction with halogens
2Li(s) + Cl2(g)  2LiCl(s)
lithium + chlorine  lithium chloride
2Na(s) + Cl2(g)  2NaCl(s)
sodium + chlorine  sodium chloride
5. Reaction with acid
The alkali metals react violently with dilute acid.
2M + 2HCl → 2MCl + H2

21. Usesof alkali metals
1. Li
Lithium carbonate is sometimes used to treat mental
illnesses such as depression.
LiHCO3 is used as a removing agents in gout.
2. Na & K
a) Na+ is the most abundant cation in extracellular
fluids.
b) It is the main contributor to osmotic pressure and
hydration; and plays a fundamental part in the
electrical activities of the body (e.g., nerve impulse
transmission and muscular contraction).
c) A decreased concentration of sodium in the blood
produces Hyponatremia. If serum sodium levels drop
rapidly, seizures may occur.
d) An increased level of sodium in the serum is called
Hypernatremia.

22. Na & K
K:
a) A mineral element that serves as both the principal
cation in intracellular fluid and an important
electrolyte in extracellular fluid.
b) An abnormally low concentration of potassium in the
blood is called Hypokalemia.
c) An excessive amount of potassium in the blood is
called hypokalemia.
d) Along with other electrolytes (e.g. magnesium,
calcium, chloride), sodium and potassium participates
in many functions, including cell membrane
homeostasis, nerve impulse conduction, and muscle
contraction.

23. 3.NaCl & KCl
a) Hypertonic solution of NaCl is used to prevent the
corneal edema.
b) Isotonic solution of NaCl is used as irrigation fluid.
c) 6% NaCl solution is used as preservative.
d) KCl is used as dirutics.
e) NaCl and KCl are the major components of ORS.
f) Oral potassium chloride is given in attacks accompanied
by hypokalemia.
g) Iodized salt. A salt containing 1 part sodium or potassium
iodide to 10,000 parts of sodium chloride. It is an
important source of iodine in the diet. Its use prevents
goiter due to iodine deficiency
h) Lactated R.’s solution: A crystalloid electrolyte sterile
solution of specified amounts of calcium chloride,
potassium chloride, sodium chloride, and sodium lactate in
water for injection. It is used intravenously to replace
electrolytes.

24. 4.NaHCO3
a) Sodium bicarbonate is given in metabolic acidosis.
b) It is used in the treatment of tubular acidoses as
well as Severe or progressive hyperkalemia.
c) In the pancreatic juice it neutralizes the acidity of
the chyme entering the duodenum from the stomach
and prevents irritation of the duodenal mucosa.
d) In the renal tubular acidosis sodium bicarbonate is
used as Alkali for effective treatments.
e) Sodium bicarbonate is used as uricosuric agent to
alkalinize urine and keep uric acid crystals in
solution.

25. 4.NaHCO3
NaHCO3 is also used
a) As an antacid.
b) As a buffering agent in the biological system.
c) As a component of ORS.
d) In the preparation of effervescent agents.
e) In the treatment of CH3OH poisoning.
f) As backing powder.

26. 5.Na-CMC
Na-CMC is used as suspending agent.
6.KI
It is used
a) In Lugol’s solution :A strong iodine solution used in iodine
therapy.
b) As resorbent to promotes the absorption of abnormal
matters, as exudates or blood clots
c) As a component of iodized salt.
d) Orally administered potassium iodide is used to protect
the thyroid from radioactive iodine.