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MolE03 The
smallest particles of magnesium during combustion
Right and middle:
The sketch (Schuphan Knappe, Chemie Buch Verlag
Diesterweg 1988, S. 21) illustrates what happens with
the smallest particles of Mg and O during the combustion
of magnesium.
* Middle left:
The magnesium atome in the lattice
release single Mg atoms.
Mg(s) ----heating----> Mg(g).
(s=solidt, g=gaseous)
* Middle center:
The heat of the flame cracks each oxygen molecule into two
atoms:
O2(g)---heating--->
2 O(g).
* Middle right:
(Magnesium and oxygen atoms have to exchange electrons to form positive
and negative ions first; see explanation of right photo).
Now they can form a new
crystal
lattice MgO(s) releasing the huge quantities of heat and light
energy observed
* Right:
Magnesium atoms (12Mg) have 2 electrons
more
than atoms of the noble gas neon (10Ne),
oxygen atoms
(8O) have 2 electrons less
than atoms of the noble gas neon (10Ne).
An electron
transfer between Mg and O atoms takes place:
Mg donates
two electrons, O accepts these 2 electrons, both are transformed into ions
with a double charge:
Mg - 2e-
--->
Mg2+
O + 2e- ---> O2-
These ions resemble
the noble gas neon (10Ne) in their electron number but not in
reactivity.
Mg ions and
O ions attract each other forming the lattice mentioned above:
Mg2+
+ O2- ---release of heat
and light---> MgO(s)
back.......
go
on........................................................................................................last
modification: 25.10.2001