organizing elements
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Chapter 4.2
Organizing the Elements
Page 131
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The 1st Periodic Table• In 1869, there were 63 known
elements. – These included a few gases, 2 liquids and
the rest solids.– Some reacted very violently and some
reacted very slowly.
• A Russian Scientist, Dmitri Mendeleev, discovered that there were patterns that applied to all of the elements. He arranged them in a table, the periodic table of elements.
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The Periodic Table
Dimitri Ivanovich Mendeleev (1834-1907)
• Born in Siberia the youngest of 17 children!
• Refused admission to the university
• Became a school teacher• Loved to play Patience,
a card game like solitaire
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The Periodic Table
• He began to group elements that had similar chemical and physical properties
• Then grouped according to atomic mass and bonding power
• Saw patterns among the elements
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Mendeleev’s Discoveries– He knew that some elements have similar
chemical and physical properties and thought that these similar properties were the secrets to a hidden pattern.
– To discover this pattern, Mendeleev wrote down each element’s melting point, density, atomic mass and color on individual cards.
– When arranging the cards in various ways, Mendeleev noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass.
– Group by group, this arrangement became known as the 1st periodic table!
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Predicting New Elements…
• After arranging the 63 known elements there were 3 blank spaces.– These spaces were elements that
had not yet been discovered and he was even able to predict these unknown elements’ chemical and physical properties! WOW!!!
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The Modern Periodic Table
• Since Mendeleev’s 1st periodic table, the modern periodic table contains more than 100 elements.
• In the modern periodic table, the elements are arranged in order of increasing atomic number.
• The properties of an element can be predicted from its location on the periodic table.
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Divisions of the Periodic Table
• The Periodic Table can be broken up into 4 general categories:– The metals– Nonmetals– Inert Gases– Semimetals
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The Periods in the Periodic Table…
• Periods: The periodic table is organized into horizontal rows called periods.– Periods contain a series of different elements– The periodic table contains 7 periods – the number
of electron levels• Period 1 has 2 elements• Periods 2 and 3 each have 8 elements• Periods 4 and 5 have 18 elements• Period 6 has 32 elements• Periods 6 and 7 are placed off the table to save space
and are known as the lantahnides and actinides.
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Periods Cont.• From Left to Right the
elements change in a predictable pattern:– Metals are located on the
left where as nonmetals are located on the right.
– Atoms increase in mass from left to right
– Atoms increase in size from top to bottom, but decrease in size from left to right
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The Groups in the Periodic Table…
• The vertical columns of the periodic table are called groups (or families).
• Groups are also known as “families” (groups of elements with similar characteristics)
• Patterns can also be predicted from groups.– Examples:
• Each element in each group contains the same number of valence electron (the number of electrons in the outer most energy level)
• Each family of elements generally reacts the same with other groups (all group 1 elements react very violently with group 17 elements)
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Reading the Periodic Table• Each square in the periodic table contains lots of
information. In your textbook it contains 4 pieces of information:– An element’s atomic number– An element’s chemical symbol
• This is a representation of an element, consists of 1 or 2 letters.
– An element’s name– An element’s atomic mass.
Atomic number
Element name
Chemical Symbol
Atomic Mass