Transcript The Periodic Table - Ursuline High School

The Periodic Table:
An Introduction
Invention of the Periodic Table


Elements vary widely in their properties, but
some elements have similarities in their
properties.
The first to notice that these properties varied
in a regular pattern was John Newlands.
 He
arranged the first 16 elements known at the time
(except hydrogen) in order of increasing mass and
then placed them in two rows.
 He noticed that the two sets of elements had similar
properties. Because the properties repeated with
the eighth element, he called his pattern the law of
octaves.
John Newland’s octaves
Li Be
Na Mg
B
Al
C
Si
N
P
O
S
F
Cl
Mendeleev and the Periodic Table

In 1870, the Russian chemist Dmitri Mendeleev
arranged all 63 known elements in such a way
that:
 They
were in order of atomic mass.
 They were arranged in a table in such a way that
elements with similar properties were arranged in
vertical columns.
 When this was done, the patterns of properties clearly
repeated themselves in a periodic fashion.
Exceptions to the pattern

Mendeleev had to reverse the order of two
elements, tellurium and iodine.
 He
assumed that the atomic weights were in error.
 When isotopes were discovered, it was found that he
had correctly placed these elements in the order of
their atomic numbers.

Mendeleev also predicted that additional
elements would be discovered to fill in gaps that
he left to make the properties line up.
The Modern Periodic Table
http://serc.carleton.edu/images/usingdata/nasaimages/periodic-table.gif
Horizontal Rows are called periods.
Vertical columns are called groups.
Groups have similar properties.
The elements are divided into three main groups:
Metals
Semi-conductors or metalloids
Nonmetals
Metals vs. Nonmetals

Metals
 are
good conductors of electricity.
 except for mercury, are solids at room temperature.

Nonmetals
 are
poor conductors of electricity.
 exhibit a wide variety of properties.
 may be solids, liquids or gases at room temperature.
The alkali metals are very reactive, having only one
electron in their outer shells. They tend to be very
soft.
The alkaline-earth metals are reactive, but not as reactive as the
alkali metals. They are harder and have higher melting points
than the alkali metals.
Transition metals have outer electrons in d orbitals.
They are generally not as reactive as the alkali or
alkaline-earth metals.
Semiconductors or metalloids conduct electricity better
than nonmetals but not as well as metals.
Halogens are nonmetals which are very reactive. They
tend to form salts with metals.
The noble gases are nonmetals which are very inert, or
unreactive. Their full outer shells account for this property.