periodic table
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NOTES
The Periodic Table
In 1869, Mendeleev proposed a periodic table where elements were arranged by atomic weights showing chemical periodicity in rows. Moseley is recognized to be the father of the modern periodic table where elements are arranged by atomic numbers.
Characteristics of elements in group 1
They form:
Chlorides with the general formula MCl (M represents any member of the group)
Example:
2 Na + Cl2 --> 2 NaCl
2 K + Cl2 --> 2 KCl
Oxides with the general formula M2O
Example:
4 Na + O2 --> 2 Na2O
4 K + O2 --> 2 K2O
Hydrides with the general formula MH
Example:
2 Na + H2 --> 2 NaH
2 K + H2 --> 2 KH
Peroxides with the general formula M2O2. Cs explodes in contact with O2 or air.
Example:
2 Na + O2 --> Na2O2
Bases with the general formula MOH
Example:
2 Na(s) + 2 H2O(l) --> 2 NaOH(aq) + H2(g) + heat
They are soft metals obtained by electrolysis of their fused salts.
Example:
2 NaCl(s) + electricity --> 2 Na(l) + Cl2(g) (Na(l) is then cooled to obtain solid Na)
They have relatively low melting, boiling points and density.
Characteristics of elements in group 2
They form:
Chlorides with the general formula MCl2 (M represents any member of the group)
Example:
2 Ca + Cl2 --> 2 CaCl2
Oxides with the general formula MO
Example:
2 Mg + O2 --> 2 MgO
Hydrides with the general formula MH2
Example:
Ba + H2 --> BaH2
Bases with the general formula M(OH)2
Example:
2 Be(s) + 2 H2O(l) --> 2 Be(OH)2(aq) + H2(g) + heat
They react with halogens to give a general formula of MX2 (X represent any members of group 17)
Example: 2 Mg + Br2 -->2 MgBr2
They have higher boiling, melting points, and density then group 1 elements
They are harder metals then group 1 elements.
The transition elements in group 3-12
Many transition elements and their aqueous solutions are brightly colored such as Cr, Cu, and Ni.
They have multiple oxidation states due to more then one unfilled orbital; the inner d and outer s orbital.
The inner-transition elements
The lanthanide series
The actinide series
The carbon family
Carbon has three allotropes: Diamond, graphite (graphite is a good conductor of electricity but diamond is not) and buckminsterfullerene
The nitrogen family
N2 makes up 78% of the atmosphere by volume.
N forms very unstable compounds that decompose explosively such as nitroglycerine and trinitrotoluene TNT.
N2(g) is produced by liquefying air at -200 oC which is warmed up to -196 oC (the boiling point of N2) and collected as a gas.
N is used in artificial fertilizers and explosives.
P occurs chiefly in compounds such as calcium phosphate Ca3(PO4)2 that are found in all living things.
Example:
Phosphate is present in teeth and bones.
The oxygen family
O has 2 allotropic forms O2 and O3 (ozone) a bent molecule.
O2 makes up about 21% of the atmosphere by weight.
Color of some gases
H2 colorless
N2 colorless
O2 colorless
F2 green
Cl2 yellow green
NO2 orange
Color of some liquids
Ag silvery gray
Br2 dark red
Color of some solids
Cu brownish
I2 steel gray
Zn dull gray
Ag silver gray
Color of some oxides
Oxide of Fe (rust) orange brown
Oxide of Cu (patina) green
Oxide of Ag (tarnish) gray silver
Oxide of Zn whitish
Color of some metal solutions
Cu in solution is blue
Pb in solution is yellow
Atmospheric gaseous composition
N2(g) 78%, O2(g) 21%, Ar(g) 0.9%, + other gases
Sublevel filling blocks
s block (groups 1 and 2)
p block (groups 13-17)
d block (groups 3-12)
f block (lanthanides and actinides series)
