Alkali metals - PeriodicTableGroups-9H - home

gapingthingsΠολεοδομικά Έργα

15 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

67 εμφανίσεις

Alkali meta
l
s























2/ Explanation of the uses of the elements



H

-

Hydrogen

has applications in
physics

and engineering.
Hydrogen

is used as a
shielding gas for
welding
, isolating the site of the weld from atmospheric gases such
as
oxygen

and nitrogen. It is used for cooling rotors in electrical pow
er generators
because of its high thermal conductivity. Liquid
hydrogen

is colder than 14
Kelvin
,
and is used for research in cryogenics and superconductivity.



L

-

Lithium stearate is mixed with o
ils to make all
-
purpose and high
-
temperature
lubricants. Sometimes, lithium
-
based compounds such as lithium carbonate (Li
2
CO
3
)
are used as drugs to treat manic
-
depressive disorders.



Na

-

Sodium metal is used in the preparation of tetraethyl lead, PbEt
4
, an

important
anti
-
knock reagent in leaded petrol (gasoline)
-

fortunately being phased out in many
countries because of lead pollution problems. Sodium vapour is used in lamps for
street lighting.



K

-

The superoxide KO
2

is used in breathing apparatus where moisture in the breath
and carbon dioxide reacts with it to release oxygen [2KO
2

+ H
2
O + 2CO
2

→ 2KHCO
3

+ O
2

]. The alloy of potassium with sodium (NaK) is used as a heat
-
transfer medium
in nuclear reactors. The alloy i
s liquid at ambient temperature and is a good reducing
agent in the chemistry laboratory.



Rb
-

Rubidium is easily ionized, and so has possible use in "ion engines" for space
vehicles. Rubidium used as a "getter" in vacuum tubes and can be used for making
s
pecial glasses.



Cs
-

Caesium
is
used as a catalyst in the hydrogenation of a few organic compounds

and can be used in atomic clocks. Caesium is used in photoelectric cells and vacuum
tubes.



Fr
-

Francium has no uses.





3/ Explanation of any trends in
behaviour within the group

All alkali metals reacts to water and the reaction becomes further vigorous the lower down
the column in the periodic table directly straight to the heaviest alkali metals. Their chemical
reactions with water are as follows:

Alk
ali metal + water → Alkali metal hydroxide + hydrogen gas

4/
The structures/compounds the elements form


Lithium hydride

Lithium nitride

Lithium carbonate

Lithium fluoride

Sodium iodide



Sodium chloride

Sodium hydride

Sodium fluoride

Sodium iodide





Potassium chloride

Potassium hydride

Potassium fluoride

Potassium iodide



Rubidium chloride

Rubidium hydride

Rubidium fluoride

Rubidium iodide



Caesium chloride

Caesium hydride

Caesium fluoride

Caesium iodide









Lily &

Jasmine