Mendeleev’s Periodic Table
1869, Mendeleev discovered that the elements had some sort of
pattern when organized by their atomic mass.
Mendeleev then decided to organize the periodic table by
properties of elements as well as by mass.
Although, by arranging this way, there were a few blank spots,
Mendeleev predicted that those spots would one day be filled
up. And they were! (Germanium, Gallium, Scandium)
Current Periodic Table
Our current periodic table contains 113 elements!
Although it is organized differently than Mendeleev’s table, it is
still organized based on atomic information. NOW we organize
by increasing atomic number (# of protons)
By using the periodic table, you can predict the properties of an
atom, based on it’s location on the table!
Organization of the Periodic Table
PERIOD: The periods on the periodic table (see the
connection there??) are the horizontal rows.
Elements within the periods are different from one another. They
increase in mass and atomic number as you move from the left side
of the row to the right and they vary in properties and type.
GROUPS/FAMILIES: The groups on the periodic table are the
Elements that are in the same group/family share the same
properties and characteristics with one another. As you move from
the top of the group to the bottom the reactivity generally increases
(if the characteristic is that they are reactive).
Details of Element Symbols
Each square in the periodic table contains four important
pieces of information regarding the atoms of that element:
Elements Atomic Number (the number of protons)
Elements Atomic Mass (the mass of the protons and neutrons)
Elements Atomic Symbol (usually of Latin roots)
Elements Name (not always included, but is handy when it is!)
Metals are the majority of the elements on the periodic table
Metals have four main physical properties:
Ductile (can be pulled or stretched into wires)
Thermal Conductor (conducts heat)
Malleable (can be hammered or rolled into flat sheets)
Electrical Conductor (conducts electricity)
Metals have two main chemical properties:
Reactive (they react with other elements)
Corrosive (they corrode/gradually wear away)
Important Metallic Groups
Group 1: Alkali Metals
The most reactive of all of the elements
Their reactivity increases as you move from the top towards to
Group 2: Alkaline Earth Metals
The second most reactive elements
Nonmetals are elements on the periodic table that lack the
properties of metals
Properties: Most are…
Poor conductors of electricity
Poor conductors of heat
Semimetals are a hybrid of metals and nonmetals. They have
properties of both!
Properties of semimetals are
They are solids at room temperature
They are brittle
They are hard
They are able to conduct electricity (very valuable!)
Inert Gases/Noble Gases
The inert/noble gases are very important!
Inert/noble gases do NOT react with ANY elements!
Due to their extremely lo reactivity, they were not discovered for
a very long time after most of the other elements!
The “neon” lights that you see in store windows are filled with
inert/neon gases (although they are typically not filled with neon
itself. Usually they are filled with Xenon or Argon).