 Patterns
exist
 Scientists seek
everywhere –. They explanations for
occur in regular
observed
occurring shapes & patterns and for
structures and in
the similarity and
repeating events &
diversity within
them.
 relationships.
Dmitri Mendeleev
Father of Periodic Table
For many years scientists had been
struggling to come up with patterns in
the elements. Elements are a substance
that cannot be broken down. Mendeleev
was creating his table before the time
when detailed discoveries about the
atom had been conducted.
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In 1869, Dmitri Mendeleev decided on a plan to organize the elements.
He wrote facts about all of the known elements on paper cards.
He included information about the elements physical and chemical properties.
He looked for clues about how those elements compared to each other.
He studied the patterns of the elements.
He was able to organize the elements at the time in order of their atomic mass.
He realized that the physical and chemical properties of elements were related to
their atomic mass in a ‘periodic’ way. He arranged them so that groups of
elements with similar properties fell into vertical columns in his table.
Mendeleev’s Periodic Tables
Notice the gaps that he
was not able to fill in.
He predicted the atomic
mass of new elements
that would later be
found!
The table at the left was
Mendeleev’s first sketch
Of the periodic table.
The table at the right was
the table that Mendeleev
published in 1869.
Alien Periodic Table
Horizontal Patterns:
*Number of fingers increased by
one.
*The body shape was all the same.
*They all had their first four fingers
on their left hand. When there was
more than four fingers, they had a
right arm and hand.
Vertical Patterns:
*They had a characteristic that
grew by one. (horns, hair, foot
length, stripes, hat, hair length,
tufts, number or legs)
*They all had the same number of
fingers.
* Body shape progressed from
triangle to circle to rectangle to
oval to upside-down triangle.
Current Periodic Table
The table is organized from top to bottom and left to right by the number of protons.
The table is organized from top to bottom and left to right by the atomic mass.
Metals and Non-metals
 Most
metals are found on the left side of
the table and the non-metals to the right.
Groups
 18
vertical columns called GROUPS or
FAMILIES
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Elements in each group have similar
characteristics.
Elements share similar physical and chemical
properties.
The groups are
often referred to
as group 1 through
group 8.
Periods
 Series
of different elements that are not
alike in properties, but they have
progressive patterns.
 Pattern from left to right is reactive to
non-reactive.
 The number of outer
electrons increase by
one left to right.
Physical Properties of the
Periodic Table
Group two elements are known as the alkaline
earth metals. They are all silver-colored and
soft, and have relatively low densities,
melting points, and boiling points.
Chemical Properties of the
Periodic Table
Group 17 elements are called halogens. They are extremely
reactive. Due to their e high reactivity (electronegativity),
they are not found in their elemental form in any natural
environment on Earth. They are generally toxic, or even
lethal, to biological organisms in their elemental forms.
*The number of the period indicates how many electron orbitals there are in each atom.
*As you move across the period, the number of electrons in the outermost orbital increases
by one.
*In a group, the outermost orbital has the same number of electrons.
*Because electrons are the outermost particles in an atom, they are the ones that give an
atom it’s properties, so elements with similar outer orbitals, have similar properties
Group 1 - Has one outside electrons. They are very reactive metals that react violently with water.
Group 2 – Have two outside electrons. They are soft, silver metals that are reactive with oxygen.
Group 17 – Have 7 outside electrons. They are very reactive nonmetals.
Group 18 – Have 8 outside electrons. They are very nonreactive gases. (noble gases)