Book
• Inorganic Chemistry – Catherine E. Housecroft
and Alan G. Sharpe
LESSON 1: ALKALI METALS
NAME OF ALKALI METALS
Li
Na
K
Rb
Cs
Fr
Overview
IONIZATION ENERGY
Body-centered cubic
Melting points and boiling points
1330
892
180
Li
Boiling
points
Nhieä
t ñoä
soâ
i
Melting
points
Nhieä
t ñoänoù
ng chaû
y
760
688
690
98
64
39
29
Na
K
Rb
Cs
Hardness
Cut Li
Cut Na
Cut K
Flame
Flame test
1. Overview
- Electronic configuration: [Noble gas]ns1
- Francium is a radioactive element with very low half-life.
- Ionization energies of metals: low
- Structures of metal lattices: body-centred cubic lattice
- Hardness: soft
- Melting and boiling points: low
- They produce a characteristic colour to the flame
reflective of their emission can be used for their
identification.
2. Reactivity
M 
 M + 1e
+
•They tend to lose the outer shell electron to
form cations with charge +1 (monovalent
ions).
•These metals are highly electropositive and
form compounds which are ionic in nature
Chemical reaction
Halide
Metallic hydrides
They are
always stored
under
kerosene
*With H2O:
M + H2O  MOH + ½ H2
Basic hydroxide
The reaction of the metal is exothermic
• With NH3:
M + NH3
MNH2 + ½ H2
(Alkali metal amides)
The amide is hydrolyzed to ammonia.
NaNH2 + H2O → NaOH + NH3
• With acid:
M + HCl
MCl + ½ H2
• With carbon:
2(Li, Na) + 2C
M2C2
2(K, Rb, Cs) + nC
MCn
Anomalous Behaviour of Lithium
• Reacts slowly with oxygen to form a normal oxide
• Lithium reacts very slowly with water.
• Lithium hydroxide is less basic and decomposes back into
oxide and water.
• Lithium carbonate is less stable due to covalent nature and
decomposes into oxide and carbon dioxide.
• It reacts with atmospheric nitrogen to form nitride.
• Lithium nitrate decomposes into nitrogen dioxide, oxygen and
oxide, while the other nitrates of alkali metals yield nitrites and
oxygen.
• Lithium salts are less soluble compared to other alkali metal
salts.
Diagonal
Relationships
The elements in
each encircled
pair have
several similar
properties.
Diagonal Relationship of Lithium with
Magnesium
• Lithium of alkali metal group resembles more with
the magnesium of alkaline earth metal group.
• Lithium and Magnesium are relatively harder metals with
higher melting points.
• Both slowly react with water to liberate hydrogen.
• Water hydrolyzes both nitrides to liberate ammonia.
• Both form normal oxides which are less soluble in water.
• Both form carbide which on hydrolysis yields acetylene.
• Bicarbonates of lithium and magnesium are stable only in
solution and not in solid form.
Extraction
• Molten Electrolytic process:
molten electrolysis
2MCl 
 2M + Cl2
• Sodium is manufactured by the Downs process in which molten
NaCl is electrolysed; CaCl2 is added to reduce the operating
temperature to about 870 K, since pure NaCl melts at 1073 K.
• K:
Na + KClmolten → NaCl + K(gas)
• Rb, Cs:
Ca + 2CsCl 
 CaCl2 + 2Cs
molten
Ca + 2RbCl 
 CaCl2 + 2Rb
molten
3. Occurrence
• Sodium and potassium are abundant in the Earth’s
biosphere (2.6% and 2.4% respectively) but do not
occur naturally in the elemental state:
- Rock salt (almost pure NaCl)
- Natural brines and seawater
- Sylvite (KCl), Sylvinite (KCl/NaCl) and carnallite
(KCl.MgCl2.6H2O).
- In contrast to Na and K, natural abundances of Li, Rb
and Cs are small (% abundance Rb > Li > Cs)
Some minerals of alkali metals
Sylvinite: KCl.NaCl
Orthoclas: KAlSi3O8
Albite: NaAlSi3O8
Carnallite: KCl.MgCl2.6H2O
Lepidolite: Li, Rb, Cs
4. COMPOUNDS OF ALKALI
METALS
• Oxides, peroxides , superoxides
• Hydroxides MOH
• Halides
• Salts of oxoacids: M2CO3 and MHCO3
Oxides
• Reaction with oxygen produces several ionic
oxides.
• In excess oxygen:
- Li forms oxide, Li2O.
– Na forms the peroxide, Na2O2.
– K, Rb and Cs form the superoxide MO2.
• Oxides: Thermal decomposition of the peroxides
or superoxides.
t0
2M 2O2 
 2M 2O + O2
2LiOH 
 Li 2O + H 2O
t0
• Li2O and Na2O: white crystals
• K2O: pale yellow
• Rb2O: yellow
• Cs2O: orange.
All the oxides are strong bases, the basicity increasing
from Li2O to Cs2O.
Peroxides and superoxides
• Sodium peroxide (Na2O2) is colourless (faint
yellow is due to the presence of small amounts of
NaO2).
• The alkali metal oxides, peroxides and superoxides
react with water.
Li2O + H2O → 2LiOH
Na2O2 + 2H2O → 2NaOH + H2O2
2KO2 + 2H2O → 2KOH + H2O2 + O2
Na 2 O2 + CO 
 Na 2 CO3
2Na 2 O2 + 2CO2 
 2Na 2 CO3 + O2
KO2 + 2CO2 
 2K 2 CO3 + 3O2
Air purification
Hydroxides
• Hydroxides of alkali metals are strong bases.
• Reactions with CO are of interest since they give
metal formates:
• Amphoteric metals, react with aqueous MOH:
• Hydroxides are produced by the electrolysis of an
aqueous solution of brine.
Structures
Each ion is
surrounded
by
eight
others
of
opposite
charge.
Each Na+ and
Cl ion is 6coordinate in
the
crystal
lattice
Salts of oxoacids
• The hydroxides are alkaline which react with carbon
dioxide to carbonates.
2NaOH + CO2 → Na2CO3 + H2O
• Alkali metal carbonates (except lithium carbonate)
are ionic, thermally stable, and water-soluble.
Properties
* Thermal decomposition
2NaHCO3 → Na2CO3 + CO2 + H2O
* With acid:
NaHCO3 + HCl → NaCl + CO2 + H2O
Na2CO3 + 2HCl →
2NaCl + CO2 + H2O
* With alkaline solution:
NaHCO3 + NaOH → Na2CO3 + H2O
What is soda?
NaHCO3 or Na2CO3
Sodium carbonate
Sodium bicarbonate
Na2CO3.10H2O
Na2CO3 (soda ash-washing soda)
Are
solutions
of soda
ash acidic
or basic?
Uses
• Washing soda is used for removing burnt-on
grease from kitchen utensils.
• It is prominently used in soap, glass and paper
industries.
• It also helps in the removal of the permanent
hardness of the water.
NaHCO3 (Baking soda)
• Reduces the acidity in the stomach
• Used in the process of washing as a
water softener
• Due to the formation of soapy foam, it
is used in fire extinguishers
• Removes the dirt off materials without
damaging the properties of the material
NaHCO3 (Baking soda)
2.What happens when you mix baking soda and lemon
juice?
When baking soda is mixed with lemon juice, bubbles are
formed. These bubbles are formed due to the evolution of
carbon dioxide gas.
3. Why do athletes take sodium bicarbonate?
During high-intensity workouts, our body releases lactic acid.
This acidity is directly related to pH levels in our bodies
!!!!Some
people
effects
vomiting, bloating,
causing
our experience
muscles tosideburn
andsuch
feelas fatigued.
Sodium
andbicarbonate
gas. It’s a good
idea
speak
a healthcare
professional
clears
thetoacid
out with
of muscle
cells, helping
restoreto
make
it’s right
an sure
optimal
pH. for you before trying it.
Ernest Gaston Joseph
Solvay
(16 April 1838–26 May
1922)
a Belgian chemist, indust
rialist and philanthropist.
Solvay process