- Alkali metals have low ionization energies and readily lose their outer electron to form cations with a +1 oxidation state. They are soft, reactive metals that form ionic compounds. - Sodium is the second alkali metal and is found abundantly in nature as the mineral sodium chloride. It is extracted commercially via the Downs process, which involves electrolysis of molten sodium chloride at lower temperatures using calcium chloride. This allows pure sodium to be produced at the cathode and chlorine gas to be collected at the anode.

1. Alkali metals

2. Periodic discussion and general characteristics of
alkali metals:
Electronic configurations
All the alkali metals have one electron in their outermost 's' orbitals
preceded by the noble gas configuration. Thus, the general
configuration of alkali metals may be written as [Noble gas] ns1 where
'n' represents the valence shell. The electronic configurations of alkali
metals are:
The electronic configurations of alkali metals are as follows:

3. Element Symbol Atomic No.
Electronic
configuration
Lithium Li 3 [He]2s1
Sodium Na 11 [Ne]3s1
Potassium K 19 [Ar]4s1
Rubidium Rb 37 [Kr]5s1
Cesium Cs 55 [Xe]6s1
Francium Fr 87 [Rn]7s1

4. GENERAL CHARACTERISTICS OF ALKALI METALS:
Atomic and ionic radii:
Being the first elements of each period, alkali metals have the largest
atomic and ionic radii in their respective periods. As we move within a
period, the atomic radius and ionic radius tend to decrease due to
increase in the effective nuclear charge. On moving down the group,
there is increase in the number of shells and, therefore, atomic and
ionic radii increase.

5. Ionization energies
Alkali metals have the lowest ionization energy in each period. Within
the group, as we go down, the ionization energies of alkali metals
decrease due to their atomic size being the largest in their respective
periods. In large atoms the valence electrons are loosely held by the
nucleus and are easily lost, leading them to have low ionization
energies and acquiring stable noble gas configurations. On moving
down the group, the atomic size increases and the number of inner
shells also increases, increasing the magnitude of screening effect and
consequently, the ionization energy decreases down the group.

6. Melting and boiling points
All alkali metals are soft and have low melting and boiling points. As
alkali metals have only one valence electron per metal atom, the
energy binding the atoms in the crystal lattice of the metal is low.
Consequently, the metallic bonds in these metals are not very strong
and their melting and boiling points decrease on moving down the
group.

7. Electropositive or metallic character:
The electropositive character of an element is expressed in terms of the
tendency of its atom to release electrons
All the alkali metals are strongly electropositive or metallic in character,
since they have low ionization energies and their atoms readily lose the
valence electron. As the ionization energies decrease down the family,
the electron releasing tendency or electropositive character is expected
to increase down the family.

8. Oxidation states:
All alkali metals have only one electron in their valence shell. They
exhibit an oxidation state of +1 in their compounds and can lose the
single valence electron readily to acquire the stable configuration of a
noble gas. Thus, they form monovalent ions, M+(e.g., Li+, Na+, K+, Rb+,
Cs+). Thus, alkali metals are univalent and form ionic compounds.

9. Characteristic flame coloration:
As the alkali metals have very low ionization energies, the energy from
the flame of a Bunsen burner is sufficient to excite the electrons of
alkali metals to higher energy levels. The excited state being unstable,
these electrons return to their original energy levels, emitting extra
energy, which gives characteristic flame colorations. The different
colours of the alkali metals can be explained on the basis of amount of
energy absorbed for excitation of the valence electron.

10. Element Li Na K Rb Cs
Flame colour crimson red yellow pale violet violet bluish

11. Soft metals:
All the alkali metals are soft and can be cut with the help of knife.
Softness of alkali metals is due to weak metallic bonding in them
because of the larger atomic size of the atom. On moving down the
group, metallic bonding weakens and hence softness increases.

12. Nature of the compounds:
The compounds of the alkali metals are ionic in nature. Alkali metals
form cations readily by losing the valence electrons (due to the low
ionization energies and large atomic sizes). They go on to form ionic
bonds with the non-metals of the 'p' block.

13. Reducing agents:
Due to low ionization energies alkali metals have larger tendency to
loose their outermost electron and hence behave as strong reducing
agent.

14. Extraction of alkali metals:
Difficulties encountered during the extraction of
alkali metals:
1. Alkali metal are strong reducing agents and hence cannot be
extracted by reduction of their oxides or chlorides.
2. Alkali metals being highly electropositive cannot be displaced from
the aq. Solution of their salts by other metals.
3. These elements cannot be extracted by the electrolysis of aqueous
solution because the metals liberated at once react with water.

15. Why alkali metals cannot be obtained by carbon
reduction method?
Due to the following reasons
1. Alkali metals are very strong reducing agent and hence their oxides
and halides cannot be reduced by other elements or compound
chemically.
2. Alkali metals have grater affinity with oxygen or halogen atom
combined with metals than that of carbon. Hence halides of alkali
metals cannot be easily roasted to obtain their oxides.
3. High range of temperature is required for the reduction of halide or
oxides of alkali metals with carbon and at high temperature carbon
combines with alkali metals to give carbide of the metals instead of
free metals.

16. Sodium

17. Occurrence:
Sodium is the second member of alkali metals. Among the alkali
metals, it occurs most abundantly in nature. It is not found in free state
because of highly reactive nature.

18. Minerals of Sodium:
1. Albite (soda feldspar) -NaAlSi3O8
2. Borax - Na2B2O7.10H2O
3. Glauber's salt- Na2SO4.10H2O
4. Sodium chloride, (common salt) found as rock salt, in sea water and
in lakes.
5. Sodium nitrate- (NaNO3) as chile saltpetre.
Out of these minerals only NaCl has been used economically to extract
metal and hence NaCl is the ore of sodium.

19. Extraction of sodium: Sodium is extracted by the
electrolysis of fused NaCl by the process called
Down’s Process
Difficulties encountered for the extraction of sodium: Although sodium
chloride is very cheap and is abundantly available yet the development of
Down’s process for the extraction of sodium from fused sodium chloride was
delayed because of the following reasons:
1. NaCl melts at 800oc and it is difficult to attain and maintain this high
temperature.
2. Na melts at 883oc and hence at the temperature of electrolysis, the
metal liberated will vaporise.
3. Molten Na forms a metallic fog with fused NaCl and it can short circuit
the cell.
4. The products of electrolysis, sodium and chlorine are highly reactive and
can corrode the material of the cell at this high temperature.

20. Down’s cell:
In 1924, J.C Down overcome all these difficulties. He observed that the
addition of calcium chloride lowers the melting point of sodium
chloride to 600oc.
At this temperature, Na and Cl2 don’t corrode the cell, sodium doesn’t
form metallic fog with NaCl and much less energy is required to keep
the sodium chloride in molten state for electrolysis.

22. The down’s cell is the iron vessel lined inside with fire bricks. The graphite
anode is at the centre of the cell, which rises from the bottom and cylindrical
iron cathode surround the anode. Again, anode is covered by a dome shaped
vessel which provides the outlet for the escape of chlorine gas.
The cathode and anode are separated by an iron gauze which keeps the
products of electrolysis separated. When electricity is passed, the following
reaction occurs
At cathode: Na+ + e- → Na
At anode: Cl- → Cl + e-
Cl + Cl → Cl2

23. The sodium metal liberated at cathode rises up through the molten
sodium chloride and is collected in the receiver. The chlorine gas
liberated at anode escapes out. With progress of the reaction the
concentration of sodium chloride decreases, and fresh sodium chloride
is added.
Note: During the electrolysis calcium is not discharged at cathode
because calcium needs higher potential for reduction.

24. Advantages of Down’s cell:
1. Sodium metal obtained is of high purity(99.5%).
2. The starting material i.e. sodium chloride is very cheap.
3. Chlorine is obtained as valuable by product.

25. Properties of sodium:
Physical properties:
1. Sodium is a soft, silvery white metal.
2. It is lighter water, its density being 0.97 gm/cc.
3. It is malleable and ductile.
4. It imparts golden yellow flame when introduced into Bunsen flame.
5. Like other metals, it is a good conductor of heat and electricity.
When alkali metals are strongly heated in Bunsen flame, the electron
present in their outermost shells get excited and the excited electrons when
returns back to the original position, emits electromagnetic radiation which
gives rise to characteristics colour to flame.

26. Chemical properties:
1. Action of air and moisture: Sodium metal when exposed to air
tarnishes due to the formation of sodium oxide.
4Na + O2 → 2Na2O
Sodium oxide then absorbs moisture to give sodium hydroxide which
further absorbs CO2 to give finally sodium carbonate.
Na2O + H2O → 2NaOH
2NaOH + CO2 → Na2CO3 + H2O
Na is reactive metals, it reacts with O2, H2O and CO2 of air. Hence it is
always stored in kerosene oil.

27. ii. Action of water: Sodium reacts violently with water giving NaOH
and hydrogen.
2Na + H2O → 2NaOH + H2 (EXOTHERMIC REACTION)
The sodium being lighter floats over the water and runs around.
iii. With hydrogen: Sodium combines with hydrogen at 365oc to give
sodium hydroxide
2Na + H2 → 2NaH

28. iv. Action with CO2: Sodium burns in the atmosphere of CO2 giving Na2CO3 and carbon is set free.
4Na + 3CO2 → 2Na2CO3 + C
v. Action with SiO2: it reduces silica to silicon
4Na + SiO2 → Si + 2Na2O
vi. Action with ammonia: When ammonia is passed through molten sodium, it yields sodamide evolving
hydrogen gas.
2Na + 2NH3 → 2NaNH2 + H2
(sodamide)
Sodium dissolves in liquid ammonia to form blue solution.
Na + (x+y)NH3 → Na+(NH3)x + e-(NH3)y
(ammoniated electrons)(blue)
The blue colour of the solution is due to ammoniated electrons, which absorb energy corresponding to red
region of visible light, for their excitation to higher energy levels. The excited electrons when returns back to
the original position, emits electromagnetic radiation which gives rise to characteristics blue colour.