Periodic Law
Goal 6-1
Origin of the Periodic Table
 Mendeleev
proposed the first arrangement
of the periodic table.
 Arranged
 Found
by atomic mass
that as he arranged the elements,
similar properties repeated themselves.
Mendeleev’s Periodic Table
Origin of the Periodic Table
 There
were “gaps” in his table, which led
other scientists to discover new elements.
 Moseley
devised the current periodic table
which is based on ATOMIC NUMBER
The Periodic Table
 Periodic
means “repeating” pattern.
 The
periodic table groups similar elements
together (think about sections in the
grocery store).
 Grouping
makes it easier to predict the
properties of an element.
Periodic Law
 States
that the repeating chemical and
physical properties of elements change
periodically with the atomic numbers of the
elements.
Periods
 Periods:
horizontal rows of elements (7)
 Just
as the number of protons changes as
you move from left to right across the
periodic table, so does the number of
electrons.

Remember that sentences are written in rows
and end with a period.
Groups
 Groups:
Vertical column of elements on
the periodic table (18)
 Remember
that group is spelled group and
groups go up and down.
 Elements
in the same group have the
same number of valence electrons.
Groups
 Remember,
valence electrons determine
an element’s properties so all elements in
the same group have similar properties.
 What
makes them different then???
Oxidation Number
 Tells
how many electrons can be gained or
lost when an element reacts with other
elements.
 A positive
oxidation number means it will
LOSE electrons (Ex. Sodium= +1)
 A negative
oxidation number means it will
GAIN electrons (Ex. Oxygen= -2)
(Group 14 has + or – 4)
Families of Elements
 Think
of each element as a member of a
family that is related to other elements
nearby.
 Elements
are classified as metals,
nonmetals or metalloids
 Groups
families
are sometimes referred to as
Metals
 Physical
Properties: Shiny (luster), good
conductors, high density, ductile (can be
made into thin wires), malleable (can be
hammered into thin sheets) and most are
silver
 Chemical
Properties: Corrosion (wearing
away because of a chemical reaction with
water), reactivity (bond with other atoms)
Metals
Types of Metals
1. Alkali Metals: very reactive
2. Alkaline-Earth Metals: form compounds
that are found in our bodies (calcium and
magnesium compounds)
3. Transition Metals: the properties
gradually change from being more similar
to Group 2 to being more like Group 13
(Gold, Silver and Platinum)
Nonmetals
 Physical
Properties: No luster, not
conductors, brittle, not ductile, low density,
and many are gaseous (can be solids or
liquids too though)
 Chemical
 All,
Properties: Highly reactive
except for hydrogen, are on the right
hand side of the periodic table.
Types of Nonmetals
1. Halogens: Group 17 (Ex. Chlorine).
Combine with most metals to form salts.
2. Noble Gases: Inert (unreactive) and do
not form with other atoms to make
compounds
Metalloids (Semconductors)
 Properties:
shiny or dull, conductors (but
not as good as metals), ductile and
malleable
 There
are only 6 total
Lanthanides and Actinides
 Rare
 Most
earth elements
of the actinides have been
synthesized by nuclear scientists (except
for uranium and thorium)
Periodic Trends Labeling Directions
1. Label the number of valence electrons at
the at the top of each group.
2. Label the oxidation number at the bottom
of each group.
3. Label the following groups:
•
•
•
•
•
•
•
•
•
•
•
Alkali Metals
Alkaline Earth Metals
Transition Metals
Boron Group
Carbon Group
Nitrogen Group
Oxygen Group
Halogens (only group with all 3 states of matter!)
Noble Gases
Lanthanides
Actinides
Valence electrons
Valence Electrons are:
 The electrons in the outermost shell
 Responsible for atomic bonding
 Equal to the last digit of the group number
 How many valence electrons in this atom? What
group would it be in?