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INORGANIC
Part 5 Period 3 survey, group trends page
sub–index: 5.1 Period 3 survey
of individual elements
: 11. sodium :
12. Magnesium
:
13. Aluminium :
14. Silicon : 15. Phosphorus :
16. Sulfur
:
17. Chlorine :
18. Argon * 5.2 Period 3 element trends
& explanations of physical properties * 5.3
Period 3 element trends in bonding, structure, oxidation
state, formulae & reactions
Advanced
Level Inorganic Chemistry Periodic Table Index *
Part 1
Periodic Table history
* Part 2
Electron configurations, spectroscopy,
hydrogen spectrum,
ionisation energies *
Part 3
Period 1 survey H to He *
Part 4
Period 2 survey Li to Ne * Part
5 Period 3 survey Na to Ar *
Part 6
Period 4 survey K to Kr and important trends
down a group *
Part 7
s–block Groups 1/2 Alkali Metals/Alkaline Earth Metals *
Part 8
p–block Groups 3/13 to 0/18 *
Part 9
Group 7/17 The Halogens *
Part 10
3d block elements & Transition Metal Series
*
Part 11
Group & Series data & periodicity plots * All
11 Parts have
their own sub–indexes near the top of the pages
Survey
of Period
3: Na across to Ar (8 elements, Z = 11 to 18)
5.1 Survey of the individual elements Na, Mg, Al, Si,
P, S, Cl, Ar
 Z = 11
Sodium Na in Group 1 Alkali Metals
-
The
structure of the element:
-
Physical
properties:
-
Group,
electron configuration (and oxidation states):
-
Reaction
of element with oxygen:
-
Reaction
of oxide with water:
-
Reaction of
oxide with acids:
-
Behaves as a
basic oxide dissolving to form the chloride, sulfate and nitrate
salt in the relevant dilute acid.
-
Na2O(s)
+ 2HCl(aq) ==> 2NaCl(aq) + H2O(l)
-
Na2O(s)
+ H2SO4(aq) ==> Na2SO4(aq)
+ H2O(l)
-
Na2O(s)
+ 2HNO3(aq) ==> 2NaNO3(aq) + H2O(l)
-
In all cases the
ionic equation is: Na2O(s) + 2H+(aq)
==> 2Na+(aq) + H2O(l)
-
Reaction of
oxide with strong bases/alkalis:
-
Reaction
of element with chlorine:
-
Reaction
of chloride with water:
-
Reaction
of element with water:
-
Other
comments:
-
Links to
other pages on site:
 Z = 12 Magnesium Mg in Group 2 Alkaline Earth
Metals
-
The
structure of the element:
-
Physical
properties:
-
Group,
electron configuration (and oxidation states):
-
Reaction
of element with oxygen:
-
Reaction
of oxide with water:
-
It is slightly
soluble in water, and is a basic oxide forming an
alkaline solution of magnesium hydroxide
-
Mg2+(OH–)2,
of about pH12.
-
Reaction of
oxide with acids:
-
Behaves as a
basic oxide dissolving to form the chloride, sulfate and nitrate
salt in the relevant dilute acid.
-
MgO(s) + 2HCl(aq) ==> MgCl2(aq) +
H2O(l)
-
MgO(s) + H2SO4(aq) ==>
MgSO4(aq) +
H2O(l)
-
MgO(s) + 2HNO3(aq) ==> Mg(NO3)2(aq) +
H2O(l)
-
In all cases the
ionic equation is: MgO(s) + 2H+(aq)
==> Mg2+(aq) + H2O(l)
-
Reaction of
oxide with strong bases/alkalis:
-
Reaction
of element with chlorine:
-
Reaction
of chloride with water:
-
The salt
dissolves in water forming a nearly neutral solution of about
pH6.
-
or more
correctly ...
-
The solution
is slightly acidic, because the hexa–aqa magnesium ion can
donate a proton to a water molecule forming the oxonium ion,
more simply H+(aq).
-
Reaction
of element with water:
-
Very slow
reaction with cold water to form hydrogen (bubbles form slowly
on the surface) and alkaline magnesium hydroxide.
-
Ignited
magnesium will continue to burn in steam to form the white
powder of magnesium oxide and hydrogen gas and you get the same
reaction if steam is passed over heated magnesium ribbon.
-
Other
comments:
-
Links to
other pages on site:
 Z = 13 Aluminium Al in Group 3/13
-
The
structure of the element:
-
Physical
properties:
-
Group,
electron configuration (and oxidation states):
-
Reaction
of element with oxygen:
-
Reaction
of oxide with water:
-
Reaction of
oxide with acids:
-
It behaves as a
basic oxide dissolving to form the chloride, sulfate and nitrate
salt in the relevant dilute acid.
-
Al2O3(s)
+ 6HCl(aq) ==> 2AlCl3(aq) + 3H2O(l)
-
Al2O3(s)
+ 3H2SO4(aq) ==> Al2(SO4)3(aq)
+ 3H2O(l)
-
Al2O3(s)
+ 6HNO3(aq) ==> 2Al(NO3)3(aq)
+ 3H2O(l)
-
ionic equation:
Al2O3(s)
+ 6H+(aq) ==> 2Al3+(aq)
+ 3H2O(l)
-
Reaction of
oxide with strong bases/alkalis:
-
The oxide also
behaves as an acidic oxide by dissolving in strong soluble bases
to form aluminate(III) salts.
-
e.g. Al2O3(s)
+ 2NaOH(aq) + 3H2O(l) ==>
2Na[Al(OH)4](aq)
-
forming sodium
aluminate(III) with sodium hydroxide.
-
ionic equation:
Al2O3(s)
+ 2OH–(aq) + 3H2O(l)
==>
2[Al(OH)4]–(aq)
-
Therefore aluminium
oxide is an amphoteric oxide, because of this dual acid–base
behaviour.
-
Reaction
of element with chlorine:
-
Reaction
of chloride with water:
-
With a little
water it rapidly, and exothermically hydrolyses to form
aluminium hydroxide and nasty fumes of hydrogen chloride gas.
-
However, if a
large excess of water is rapidly added, a weakly acidic
solution of aluminium chloride is formed, with the minimum of
nasty fumes!
-
The solution
is slightly acidic, because the hexa–aqa aluminium ion can
donate a proton to a water molecule forming the oxonium ion.
-
Reaction
of element with water:
-
Reactions of
the hexa–aqua aluminium ion:
-
It gives a
gelatinous white precipitate with sodium hydroxide or ammonia
solution which displays amphoteric behaviour by dissolving in
excess strong alkali (NaOH(aq), NOT NH3(aq))
and acids.
-
Al3+(aq)
+ 3OH–(aq) ==> Al(OH)3(s)
-
or
[Al(H2O)6]3+(aq)
+ 3OH–(aq) ==> [Al(OH)3(H2O)3]
+ 3H2O(l)
-
[Al(H2O)6]3+(aq)
+ 6OH–(aq) ==> [Al(OH)6]3–(aq)
+ 6H2O(l) (from original aqueous
ion)
-
With aqueous
sodium carbonate solution, the hydroxide ppt. is formed, and,
because of its acidic nature, bubbles of carbon dioxide gas are
evolved.
-
2[Al(H2O)6]3+(aq)
+ CO32–(aq) 
2[Al(H2O)5(OH)]2+(aq)
+ H2O(l) + CO2(g)
-
this
process of proton donation continues until the
gelatinous ppt. [Al(OH)3(H2O)3](s)
is formed, but will not dissolve in excess of the weak
base/alkali.
-
See
Appendix 1 in Transition
Metal Chemistry pages for more examples and
equations etc.
-
No Cr2(CO3)3
is formed because of the acid–base reaction above, due to
the acidity of the chromium(III) ion. Note the similarly
highly charged and small ions
Cr3+ and
Fe3+
behave in the same way.
-
Other
comments:
-
Links to
other pages on site:
 Z = 14
Silicon Si in Group 4/14
-
The
structure of the element:
-
Non–metal
existing as a giant covalent lattice, Sin,
where n is an extremely large number, held together by
tetrahedrally arranged Si–Si bonds.
-
Physical
properties:
-
Hard high
melting solid; mpt 1410oC; bpt 2355oC;
poor conductor of heat/electricity, but with other elements
added, conducts better, hence use in microchips.
-
Group,
electron configuration (and oxidation states):
-
Reaction
of element with oxygen:
-
Reaction
of oxide with water:
-
Reaction of
oxide with acids:
-
Reaction of
oxide with bases/alkalis:
-
It is a weakly
acidic oxide dissolving very slowly in hot concentrated sodium
hydroxide solution to form sodium silicate.
-
SiO2(s)
+ 2NaOH(aq) ==> Na2SiO3(aq)
+ H2O(l)
-
or simplified ionic equation:
SiO2(s) + 2OH–(aq) ==>
SiO32–(aq) + H2O(l)
-
Reaction
of element with chlorine:
-
Reaction
of chloride with water:
-
Reaction
of element with water:
-
Other
comments:
-
Links to
other pages on site:
 Z = 15 Phosphorus P
in Group 5/15
-
The
structure of the element:
-
Physical properties:
-
Group,
electron configuration (and oxidation states):
-
Gp5;
e.c. 2,8,5 or 1s22s22p63s23p3;
Variety of oxidation states from –3 to +5 e.g.
-
PH3
(–3), P4O6 (+3), P4O10,
PCl5 and H3PO4 (+5).
-
The maximum
oxidation state is +5.
-
Reaction of element with oxygen:
-
White phosphorus ignites
spontaneously in air, which is why it is kept under water!)
-
The reaction is vigorous,
very exothermic and the phosphorus burns with a bright flame.
-
With limited
air/oxygen, on heating the phosphorus, the covalent white solid
phosphorus(III) oxide is formed.
-
With excess
air/oxygen, on heating the phosphorus, the covalent white solid
phosphorus(V) oxide is formed.
-
Reaction of the oxides with water: Both oxides are acidic, typical non–metallic element
behaviour, and both phosphorus oxides dissolve in water to form acidic solutions.
-
Phosphorus(III) oxide forms (i) phosphonic acid and (II) a
little phosphoric(III) acid, which is an isomer.
-
Phosphorus(V) oxide forms phosphoric(V) acid, no complications
here!
-
Reaction of element with chlorine:
-
With limited
chlorine, on heating the phosphorus, the covalent liquid
phosphorus(III) chloride is formed.
-
With excess
chlorine, on heating the phosphorus, the ionic*
solid phosphorus(III) chloride is formed.
-
Reaction of
oxide with acids:
-
Reaction of
phosphorus oxides with strong bases/alkalis:
-
Both oxides
dissolve in alkalis to form a whole series of phosphate(III) and
phosphate(V) salts.
-
So, with strong
bases like sodium hydroxide, the simplified equations are:
-
initially: P4O6(s)
+ 4NaOH(aq) +
2H2O(l) ==> 4NaH2PO3(aq)
-
forming the mono sodium
salt of phosphonic acid,
-
then, with excess sodium
hydroxide, you get the disodium salt of phosphonic acid
-
NaH2PO3(aq)
+ NaOH(aq) ==> Na2HPO3(aq) + H2O(l)
-
and there is NO
trisodium salt because H3PO3 behaves as
dibasic/diprotic O=PH(OH)2
-
So, overall with excess
sodium hydroxide the reaction is ...
-
P4O6(s)
+ 8NaOH(aq) ==> 4Na2HPO3(aq) +
2H2O(l)
-
P4O10(s)
+ 12NaOH(aq) ==> 4Na3PO4(aq) +
6H2O(l) sodium phosphate(V) formed from
phosphorus(V) oxide
-
If the empirical
formulae P2O3 and P2O5
are used, just halve all the balancing numbers.
-
Other than using
excess sodium hydroxide solution, other salts can be formed.
-
e.g. P4O10(s)
+ 4NaOH(aq) + 2H2O(l) ==> 4NaH2PO4(aq)
sodium dihydrogen phosphate(V)
-
or P4O10(s)
+ 8NaOH(aq) ==> 4Na2HPO4(aq) +
2H2O(l) disodium hydrogen phosphate(V)
-
Reaction of the chlorides with water:
-
Phosphorus(III) chloride hydrolyses rapidly and exothermically
to form phosphoric(III) acid or phosphonic acid (see reaction of
oxides with water).
-
Phosphorus(V) chloride initially hydrolyses to form phosphoryl
chloride (phosphorus oxychloride)
and hydrochloric acid.
-
PCl5(s)
+ H2O(l) ==> POCl3(aq) +
2HCl(aq)
-
Then on
boiling the aqueous solution, phosphoric(V) acid is formed
and more hydrochloric acid.
-
POCl3(aq)
+ 3H2O(l) ==> H3PO4(aq)
+ 3HCl(aq)
-
overall the
hydrolysis reaction is: PCl5(s)
+ 4H2O(l) ==> H3PO4(aq)
+ 5HCl(aq)
-
Reaction of element with water:
-
Other
comments:
-
Links
to other pages on site:
 Z = 16
Sulfur S
in Group 6/16
-
The
structure of the element:
-
Three solid
allotropes. Two are crystalline lattices based on S8
molecules (rhombic and monoclinic sulfur). A 3rd form is an unstable dark brown–black polymeric
form called plastic sulfur, formed when boiling sulfur is
poured onto cold water, great fun, but of little use!
-
Physical
properties:
-
Group,
electron configuration (and oxidation states):
-
Gp6;
e.c. 2,6 or 1s22s22p63s23p4;
oxidation states range from –2 to +6 e.g.
-
Na2S (–2),
S2Cl2 (+1), SO2
(+4) and H2SO4, SF6, SO3
(all +6).
-
Reaction
of element with oxygen:
-
Sulfur burns in air
with a pale blue flame to form sulfur dioxide
(sulfur(IV) oxide), with a little sulfur trioxide.
-
Sulfur trioxide
(sulfur(VI) oxide) has to be made by the industrial Contact
Process.
-
Reaction
of the oxides with water:
Both dissolve to form acid solutions.
-
Sulfur
dioxide forms the weak 'fictitious' sulfurous acid.
-
Sulfur
trioxide reacts very violently and exothermically to form the
oily liquid, strong sulfuric acid.
-
Reaction of
oxide with acids:
-
Reaction of
oxide with bases/alkalis:
-
Sulfur dioxide
dissolves in strong bases to form sulfites/sulfate(IV)s
-
2NaOH(aq)
+ SO2(g) ==> Na2SO3(aq) + H2O(l)
formation of sodium sulfite/sulfate(IV)
-
ionic equation:
2OH–(aq) + SO2(g) ==> SO32–(aq)
+ H2O(l)
-
You would NOT
attempt to react sulfur trioxide with water, the reaction is very
violent and exothermic.
-
but theoretically:
2NaOH(aq) + SO3(g) ==> Na2SO4(aq)
+ H2O(l)
-
Reaction
of element with chlorine:
-
When chlorine
is passed over molten sulfur a variety of chlorides are formed.
-
The main
product is disulfur dichloride
-
2S(s)
+ Cl2(g) ==> S2Cl2(l)
(SiCl2,
SiCl4 also possible)
-
Reaction
of chloride with water:
-
Reaction
of element with water:
-
Other
comments:
-
Links to
other pages on site:
Z = 17 Chlorine Cl
in Group 7/17 The Halogens
-
The
structure of the element:
-
Physical
properties:
-
Group,
electron configuration (and oxidation states):
-
Gp7
Halogens;
e.c. 2,8,7 or 1s22s22p63s23p5;
(oxidation state ranges from –1 to +7) e.g.
-
HCl and NaCl (–1), NaClO and
Cl2O (+1), NaClO2 (+3), KClO3
(+5), Cl2O7
and HClO4 (+7).
-
Reaction
of element with oxygen:
-
Reaction
of the oxides with water:
-
Reaction of
oxide with acids:
-
Reaction of
oxide with bases/alkalis:
-
chlorine(I) oxide
forms sodium chlorate(I) with sodium hydroxide,
-
and chlorine(VII)
oxide will dissolve to form sodium chlorate(VII)
-
Reaction
of element with water:
-
Other
comments:
-
Links to
other pages on site:
Z = 18 Argon Ar
in Group 0/18 The Noble Gases
-
The
structure of the element:
-
Physical
properties:
-
Group,
electron configuration (and oxidation states):
-
Reaction
with anything:
-
Other
comments:
-
Links to
other pages on site:
Some trend comments on the
reactions of Period 3 elements (from left to right across
period 3)
-
In terms of the reactions with
oxygen - you start very reactive metals (Na, Mg), then moderately
reactive metal (Al), a relatively unreactive non-metal (Si), a very
reactive non-metal (P), moderately reactive non-metal (S) and
neither chlorine nor argon react directly with oxygen.
-
Its not the greatest of
trends, but the individuality of each reaction, or lack of
reaction, is important.
-
However, the reaction of the
elements with water AND more crucially, the reaction of the oxides
with water clearly produce a trend from left to right of basic
(alkaline) to acidic character - see pH values in
section 5.3.
-
These points are discussed in
more detail in section 5.3.
See also
4.1 Period 2 Survey of the
individual elements, 4.2 Period
2 element trends and explanations of physical properties * 4.3 Period 2 element trends in bonding,
structure, oxidation state, formulae & reactions,
6.1 Survey of
Period 4 elements, 6.2 Period 4 element trends in physical properties, 6.3
Period 4 element trends in bonding, formulae
and oxidation state and 6.4
Important element trends down a Group
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[Mg(H2O)5OH]+(aq)
+ H3O+(aq) 
H+(aq) + HSO3–(aq) 
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