THE PERIODIC TABLE
How the Elements are Organized
John Newlands
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Arranged the known elements according to their
properties and in order of increasing atomic mass
He placed the elements in a table
Law of Octaves
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The pattern discovered by John Newlands
All elements in a given row had similar chemical
and physical properties and these properties
seemed to repeat every eight elements
Dmitri Mendeleev
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1869, produced the first orderly arrangement of
elements in the periodic table
Elements are arranged in order of increasing atomic
mass
He even predicted elements that had not been
discovered yet
Henry Mosely
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Changed the periodic table to be organized by
atomic number instead of atomic mass
Periodic Law
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States that when the elements are arranged
according to their atomic numbers, elements with
similar properties appear at regular intervals
Valence Electrons
Elements in each column of the periodic table
have the same number of electrons in their
outer energy level (valence electrons)
 It is the valence electrons of an atom that
participate in chemical reactions with other
atoms, so atoms with the some number of
valence electrons tend to react in similar ways
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Groups
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A vertical column on the periodic table
Elements in the far left column have 1 valence
electron
Elements in the far right column have 8 valence
electrons
Period
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A horizontal row on the periodic table
Elements in the same period have the same number
of occupied energy levels
Main Group Elements
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In the s and p blocks of the periodic table
The configuration of their valence electrons can be
written as ns2
Sometimes called the representative elements
because they have a wide range of properties
Periodic Table organization
Alkali Metals- Group 1
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Are metals that react with water to make alkaline
solutions
Ex.-Potassium reacts vigorously with cold water to
form hydrogen gas and the compound potassium
hydroxide, KOH
Have a single valence electron, very reactive
When they lose the valence electron they become
stable
Alkali Metals, cont.
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Stored in oil
Never found in nature as pure substances, but only
as compounds (such as NaCl)
Soft metals
Good conductors of electricity
Alkali Metals
Potassium
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Alkaline-Earth Metals
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Highly reactive, found as compounds rather than
pure elements
Slightly less reactive than the alkali metals
Have two valence electrons and must lose both to
get a stable electron configuration
Harder and have higher melting points that alkali
metals
Halogens-Group 17
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The most reactive group of nonmetal elements
because of their 7 valence electrons, only need 1
electron for a stable configuration
Often react with alkali metals which only have one
valence electron
React with most metals to form salt (Halogen means
“salt maker”)
Noble Gases- Group 18
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Unreactive, have a full set of valence electrons
Except for helium they all have an outer shell
configuration of ns2np6 (n is the period number)
Hydrogen
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Most common element in the universe
Consists of just one proton and one electron
Behaves unlike any other element
Can react with many other elements, including
oxygen
Metals
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Make up the majority of elements
Shiny
Conduct electricity
Ductile-can be squeezed into a wire
Malleable- can be hammered or rolled into sheets