Elements in periodic table
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With so many elements already found and the
possibility of more being discovered, chemists
needed a way to organize them. Many systems were
tried in order to make some sort of pattern in their
properties to match the table. The modern periodic
table, based on atomic number and electron
configuration, was created primarily by a Russian
chemist, Dmitri Ivanovich Mendeleev, and a German
physicist, Julius Lothar Meyer, both working
independently. They both created similar periodic
tables only a few months apart in 1869. Mendeleev
created the first periodic table based on atomic
weight. He observed that many elements had similar
properties, and that they occur periodically, hence
the name, periodic table. The modern periodic table
elements are ordered by atomic number (= number
of protons in the nucleus), not weight. For
example, the elements lithium, sodium, potassium,
rubidium, and cesium have similar chemical
properties. The elements that immediate follow
them, beryllium, magnesium, calcium, strontium, and
barium, also have similar chemical properties.
Elements in Mendeleev's table were arranged in
rows called periods. The columns were called
groups. Elements of each group had similar
properties.
Nonmetals
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Nonmetals:
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the elements that lack the properties of metals; most
often encountered as compounds or mixtures of
compounds;
some occur in their elemental forms and are very
important: e.g. Nitrogen (N2), oxygen (O2), carbon.
Properties:
 almost completely opposite of metals:
poor
conductors of heat and electricity (except for
graphite -- attributed to molecular structure).
 Many are solids at STP, while many others are
gases.
 All of the group 0 (18) elements (the noble
gases--mostly inert) are gases consisting of single
atoms.
 all other gaseous elements, hydrogen, oxygen,
nitrogen, fluorine, and chlorine, are diatomic
molecules--H2, O2, N2, F2, and Cl2.
 Bromine and iodine are also diatomic, but bromine is
a liquid and iodine is a solid at room temperature.
 nonmetals also lack the malleability and ductility of
the metals -- brittle
 wide range of reactivity:
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Flourine is extremely reactive, reacting readily with
almost all other elements.
Helium is inert and does not react with anything.
Metalloids
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Metalloids are the elements found along the stairstep line that distinguishes metals from non-metals.
This line is drawn from between Boron and
Aluminum to the border between Polonium and
Astatine
(exception: Aluminum -- classified under "Other
Metals”)
list of metalloids:
 B Boron,
 Si Silicon,
 Ge Germanium,
 As Arsenic,
 Sb Antimony,
 Te Tellurium,
 Po Polonium;
properties between those of metals and nonmetals.
Generally, metalloids behave as nonmetals, both
chemically and physically.
They are semiconductors: conduct electricity, but
not as well as metals.
e.g.: silicon and germanium, used in solid-state
electronics; transistors made from semiconductors
have reduced the size of electronic components to
an almost microscopic level
Representative metals
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The representative metals contain 3 main groups:
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Alkali Metals:
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alkali metals
alkaline earth metals,
post-transitional metals.
group IA (1) elements in the table
form hydroxides which are strongly basic (e.g.,
potassium hydroxide--KOH), hence the term
"alkaline"
have a very high metallic behavior and are good
reducing agents.
crystallize with a body-centered cubic lattice in
which the points are occupied by +1 ions.
sea of valence electrons throughout the entire
lattice can wander throughout the metal high
electrical conductivity and high heat conductivity.
high luster is due to the highly mobile electrons of
the lattice. Light beams hit the electrons into
oscillations, reflecting back electromagnetic
energy as light. The softness, malleability, and
ductility of the metals are due to the nature of the
forces holding the lattice together. Since there is
no net force or attraction between the ions, they
can be moved from one lattice site to another.
The Alkaline Earth Metals
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The alkaline earth metals are metallic elements in
the group IIA (2) of the periodic table. They are
called alkaline earth metals because the "earths"
of this group, lime (CaO), and magnesia (MgO), give
alkaline reactions.
All alkaline earth elements have an oxidation
number of +2, making them very reactive. Because
of their reactivity, the alkaline metals arenot found
free in nature.
They have good metallic
properties, including conductivity, reduction
ability, luster, softness, malleability, and ductility,
but not as well as the alkali metals. Their ions have
an oxidation state of +2. Like alkali metals, they
form soluble sulfides, but unlike them, they form
insoluble carbonates (calcium
carbonate -- CaCO3 -- in
hard water).
List of alkaline earth metals:
 Be Beryllium
 Mg Magnesium
 Ca Calcium
 Sr Strontium
 Ba Barium
 Ra Radium
The Post-Transition Metals
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The post-transition metals: the lower elements of
group IIIA (13), IVA (14), and VA (15), arranged in
a staircase like fashion.
Their properties have the same relationship to
the alkaline earth metals
as the alkaline earth metals have to the alkali
metals.. As you go up the
group, their metallic character gets less and less.
For example: boron, which is above aluminum in
group IIIA (13), is not a metal but
a metalloid.
While these elements are ductile and malleable,
they are not the same as the transition
elements.These elements, unlike the transition
elements, do not exhibit variable oxidation states,
and their valence electrons are only present in their
outer shell. All of these elements aresolid, have a
relatively high density, and are opaque. They have
oxidation numbers of +3, ±4, and -3.
List of post-transition metals:
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group IIIA (13): Al Aluminum, Ga Gallium, In Indium,
Tl Thallium
group IVA (14): Sn Tin, Pb Lead
group VA 15) : Bi Bismuth
Transition metals
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The 38 elements in groups 3 through 12 of the
periodic table are called "transition metals". As
with all metals, the transition elements are both
ductile and malleable, and conduct electricity and
heat. The interesting thing about transition metals
is that their valence electrons, or the electrons
they use to combine with other elements, are
present in more than one shell. This is the reason
why they often exhibit several common oxidation
states.
three noteworthy elements in the transition metals
family: iron, cobalt, and nickel -- are the only
elements known to produce a magnetic field (i.e.
that can be magnetized)
The transition metals are the subgroups of
elements intervening between groups IIA(2) and
IIIA(13) in the periodic table. They are classified
separately because of the filling of their d subshell
orbitals.
All the transition elements are metallic, but unlike
the representative metals, they are likely to be
hard, brittle, and have high melting points because
of the relatively small size of their atoms and the
existence of some covalent binding between ions.
There are exceptions, as in the case of mercury
(Hg), which is a liquid. They have high electrical
conductivity because of delocalization of the s
electrons similar to what occurs in the alkali and
alkaline-earth metals.
Transition metals, cont’d
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transition metals have a great variety of oxidation
states shown in its compounds. Because of electron
spin, unpaired electrons give rise to paramagnetism.
Paramagnetism is likely in transition metals because
of the partial filling of the d subshell and the
movement associated with the orientations of
electrons.
Color of transition metals (and some of their ionic
compounds) due to absorption of some of the
frequencies of white light  electronic transitions
in the d subshell. The stored energy is then
dissipated through heat.
transition metals also have complex ionic structures
because of the availability of d orbitals
for participating in chemical bonding.
List of transition metals:
ScScandium
Cr Chromium
Co Cobalt
Zn Zinc
Nb Niobium
Ru Ruthenium
Ag Silver
Hf Hafnium
Rh Rhenium
Pt Platinum
Ac Actinium
Ti Titanium
Mn Manganese
Ni Nickel
Y Yttrium
Mo Molybdenum
Rh Rhodium
Cd Cadmium
Ta Tantalum
Os Osmium
Au Gold
V Vanadium
Fe Iron
Cu Copper
Zr Zirconium
Tc Technetium
Pd Palladium
La Lanthanum
W Tungsten
Ir Iridium
Hg Mercury
Inner transition (rare earth) metals
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thirty inner transition metals (also called rare earth
elements) contain 2 series of elements:
 lanthanide series,
 actinide series.
All of them in group 3 of the periodic table, and the
6th and 7th periods.
One element of the lanthanide series and most of
the elements in the actinide series are called transuranium, which means synthetic or man-made.
Lanthanide series
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The lanthanide series include the 15 elements from
atomic numbers 57 (lanthanum) to 71 (lutetium).
Their electron configuration include the 4f and 5d
energy levels. Because of the closeness of those
two levels, there is considerable uncertainty in
some electron configuration assignments. All the
lanthanides form +3 ions as their principal chemical
species. It is assumed that the ions are formed by
losing the 6s2 and 5d1 (or 4f is 5d is not present)
electrons. They generally occur together, except
for promethium which has an unstable nucleus. The
richest source mineral is monazite, a complex
phosphate. They are very rare to find, hence their
nickname--"the rare earth elements." Since they
also have very similar chemical properties,
separation is very difficult, involving fractional
crystallization and ion-exchange techniques. The
lanthanides also generally have an incomplete 4f
subshell, resulting in paramagnetism.
List of lanthanides:
La Lanthanum
Ce Cerium
Pr Praseodymium
Nd Neodymium
Pm Promethium
Sm Samarium
Eu Europium
Gd Gadolinium
Tb Terbium
Ds Dysprosium
Ho Holmium
Er Erbium
Tm Thulium
Yb Ytterbium
Lu Lutetium
The Actinide series
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The actinide series include the 14 elements that
follow actinium (atomic number 89) from atomic
numbers 90 to 103. The electron configurations of
the actinides are even more uncertain than the
lanthanides because the closeness of the energy
levels and because the nuclei are unstable to
radioactive decay. Only minute amounts of some
elements are obtained because of their instability.
All of the actinides are unstable with respect to
alpha emission. The later members tend to undergo
spontaneous fission, a fact which limits the number
of elements possible. The actinides also seem to
show a variety of oxidation states, unlike the
lanthanides. Uranium, for example, has compounds
in each of the states, +3, +4, +5, and +6.
Lu Lutetium
Thorium (Th)
Pa Protactinium
U Uranium (U)
Np Neptunium
Pu Plutonium
Am Americium
Cm Curium
Bk Berkelium
Cf Californium
Es Einsteinium
Fm Fermium
Md Mendelevium
No Nobelium
Lr Lawrencium