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CHEMISTRY UNIT 5
(The Periodic Law)
Mendeleev's periodic table - the first periodic table - it
was designed by a Russian scientist.
The periodic law states that physical and chemical
properties of the elements are periodic functions of
their atomic numbers
In other words, when the elements are arranged in
order of increasing atomic number, elements with
similar properties appear at regular intervals.
The periodic table is an arrangement of the elements in
order of their atomic numbers so that elements with
similar properties fall in the same column, or group.
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Elements within the same families have similar
properties
Group I Sodium Family (Alkali Metals)
most active metals
has 1 electron in the highest energy level
charge of +1
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Group II Calcium Family (Alkaline Earth Metals)
active metals
has 2 electrons in the highest energy
level
charge of +2
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Group III Boron Family
composed of nonmetals and metals
has 3 electrons in the highest energy level
charge of +3
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Group IV Carbon Family
composed of non-metals and metals
has 4 electrons in the highest energy level
charge of +4 or -4
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Group V Nitrogen Family
composed of non-metals and metals
has 5 electrons in the highest energy level
charge of -3
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Group VI Oxygen family
mostly active nonmetals
has 6 electrons in the highest energy
level
charge of -2
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Group VII Halogens
most active nonmetals
has 7 electrons in the highest energy level
charge of -1
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Group VIII Noble gases
inert (will not react)
has 8 (octet) electrons in the highest energy level
except He which has 2
charge of 0
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Transition elements are metals, which have properties
that are not shared by any other groups of elements
The rare earth elements are made up of the lanthanide
and actinide series
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An ion is an atom or group of atoms that has a positive
or negative charge
An ion is formed when a neutral atom loses or gains one
or more electrons
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Ionization energy IE is the energy required to remove
one electron from a neutral atom
+
Ex: A + energy  A + electron
Each time an additional electron is move away from an
atom, larger amounts of energy is required. Thus the
2nd ionization energy is higher than the 1st and so on.
Low ionization energy is characteristic of a metal
(metals give up electrons easily)
High ionization energy is characteristic of a nonmetal
(non-metals don't give up electrons easily)
Electron affinity is the energy change that occurs when
an electron is acquired by a neutral atom
Ex:
A + electron --> A + energy
F + electron --> F + energy
A positive ion is know as a cation.
A negative ion is know as an anion.
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Valence electrons are those available to be lost, gained,
or shared in the formation of compounds.
Electronegativity is a measure of the ability of an atom
in a chemical compound to attract electrons.
Tendencies of the Periodic Chart