Download THE PERIODIC TABLE abbr

Organizing the Elements
 Purposes:


Organize the known elements such that it
became easy to learn chemical and physical
properties.
Create a tool that could predict the existence of
elements yet to be discovered.
 What



He Did:
Organized known elements by increasing atomic
mass.
Elements with similar properties were placed in
the same group.
Left blank spots where possible undiscovered
elements would logically fit based on mass,
physical and chemical properties.
 Supporting

Evidence:
Table allowed the successful prediction of
gallium (eka-aluminum) and other undiscovered
elements.
 Problems:

Some elements would fit in groups by mass but
not by properties, and vice versa.

See Te and I
 Organized
by increasing atomic number (not
mass).
 Elements with similar properties are in the
same group (vertical column).
 Periods (horizontal rows) are of varying
length of increasing atomic number.

Property patterns repeat with each row.
 Weighted
average of the masses of all known
isotopes of a given element.
 Measured in atomic mass units: u or amu

1 amu is 1/12 the mass of a carbon-12 atom.
 Metals





Left side of the periodic table.
Conduct electricity and heat well.
Tend to be malleable.
Tend to be solid at room temperature.
Tend to lose electrons in chemical reactions.
 Nonmetals




Right side of the periodic table.
Do not conduct heat and electricity well.
Tend to be brittle or gaseous at room
temperature.
Tend to gain electrons in chemical reactions.

Metalloids
Located on stair-step line between metals and
nonmetals.
 Have properties that are transitional from metals to
non metals.
 Elements commonly referred to as metalloids









Boron (B)
Silicon (Si)
Germanium (Ge)
Arsenic (As)
Antimony (Sb)
Tellurium (Te)
Polonium (Po)
Astatine (At)
 Elements
in a group have similar properties
because they have the same number of
valence electrons.

Helium (2 valence electrons) is in the same
column as neon (8 valence electrons) because
both have full outer energy levels. This gives
them similar properties.
1
valence electron
 Reactivity increases from top to bottom of
group.
 Francium would be the most reactive
element in this group (if it didn’t
radioactively decay so quickly).
2
valence electrons
 Differences in reactivity are shown by the
ways they react with water.
 Reactivity increases down the group.
1
– 3 valence electrons.
 Electrons are filling the d-sublevel (instead
of s or p).

d-sublevel electrons are often delocalized and
can be made to flow in certain directions.

Makes elements good conductors of electricity.
3
valence electrons
 Aluminum is the most abundant metal in
Earth’s crust.
4
valence electrons
 Except for water, most of the compounds in
your body contain carbon.

Carbon can normally bond up to four times.
5
valence electrons
 Nitrogen and phosphorus are used in
fertilizers.
6
valence electrons
 Oxygen is the most abundant element in
Earth’s crust.
7
valence electrons
 Fluorine is the most reactive element in this
group AND on the periodic table.
8
valence electrons (except for 2 in helium)
 Gases are colorless, odorless, and extremely
unreactive.

This is due to the highest energy level being
full (8 electrons, except for helium).