History of the Periodic Table
You are now ready to begin your Periodic Adventure. First, you must
begin by reviewing some historical information regarding a man
named Dmitri Mendeleev, who created the first Periodic Table of
the Elements.
Dmitri Mendeleev
Dmitri Mendeleev, a Russian scientist born in Siberia in 1834, is
known as the father of the periodic table of the elements. The
periodic table of the elements is an important tool used by students
and chemists around the world to help them understand and simplify
the often complex world of chemical reactions.
Not only did Mendeleev arrange the periodic table of the elements,
he also wrote and published a 2 volume chemistry book entitled
Principles of Chemistry as there was no thorough chemistry textbook
at the time. Mendeleev dedicated his life to research and education.
Mendeleev made it his special responsibility to educate people
wherever he went. When he traveled, Mendeleev would ride in the
third class section of the train just to share findings with peasants
over a cup of tea. Mendeleev died on January 20, 1907 at the age of
73.
The Big Task
Mendeleev set out to identify a pattern in the elements. Mendeleev
looked at many pieces of evidence and made an important
observation that some elements have similar chemical and physical
properties. Mendeleev's hunch was that these similarities were the key
to unlocking the hidden pattern of the elements. Mendeleev then
embarked on the tedious task of organizing all known information for
every element to help him decipher the pattern.
To begin his task, Mendeleev wrote facts about the elements on
individual paper cards. On these cards, Mendeleev wrote information
such as the elements' melting points, densities, colors, atomic masses
(the average mass of one atom of that element), and bonding powers
(the number of chemical bonds an element can form).
Once Mendeleev's cards were made, he tried arranging them in various
ways. Finally, Mendeleev noticed that patterns appeared when the
elements were arranged in order of increasing atomic mass.
Mendeleev's table was not perfect, however. Arranging the elements by
increasing atomic mass left three blank spaces in the table. Despite this
development, however, Mendeleev boldly proposed that these blank
spaces would be filled by elements that had not yet been discovered.
Mendeleev was even able to use the patterns in his table to predict the
properties of these undiscovered elements. The first periodic table of the
elements was published in 1869.
The word "periodic" means that there is a repeating pattern -- that is,
the properties of the elements repeat with each row -- or period -- of the
table.
Amazingly, within 16 years of Mendeleev's first periodic table, chemists
had discovered all three of the missing elements (scandium, gallium, and
germanium), and their properties were very close to what Mendeleev had
predicted.
How to Read the Periodic Table
The Periodic table is designed to help you predict what an element's physical and
chemical properties are. You can also predict what elements will bond with each
other.
First, let's look at the columns and rows of the periodic table.
Periodic Table Courtesy of Periodic Table of the Elements v. 4.0
by Kostas Tsigaridis (http://ptoe.move.to/)
Groups or Families
The vertical columns of the periodic table (there are 18) are called groups or
families. Elements in the same group or family have similar but not identical
characteristics. You will learn more about the 18 groups in a later section. You
can know properties of a certain element by knowing which group it belongs to.
Periods
The horizontal rows of the periodic table are called periods. Elements in a period
are not alike in properties. As a rule, the first element in a period is usually an
active solid, and the last element in a period is always an inactive gas. Atomic
size decreases from left to right across a period, but atomic mass increases from
left to right across a period. Atoms on the left of the period, therefore, are usually
larger and more lightweight than the smaller, heavier atoms on the right of the
period.
Think Inside the Box
When you look at the periodic table, you should notice that each box represents
a different element, and each box contains vital information about the element,
including its name, symbol, atomic number, and atomic mass. Look at the
sample box below for a description of each of these pieces of information.
6
C
Carbon
12.011
The top number is the atomic number. Every element has its own unique atomic
number. The atomic number tells how many protons are in one atom of that
element. Since no two elements have the same atomic number, no two elements
have the same number of protons.
The large letter is the element's symbol, and just below that is the element's
name. Each element has its own unique symbol and name. It is often very useful
to memorize symbols and names for elements, especially the more commonly
used elements.
Below the name is the element's atomic mass. The atomic mass is the mass in
atomic mass units for all possible isotopes of that element. The atomic mass
essentially gives you an estimate of how massive one atom of that element is.
Metals, Nonmetals & Metalloids
Metals, Nonmetals, & Metalloids
Most periodic tables contain a stair step line which allows you to identify which
elements are metals, nonmetals, and metalloids. Following are descriptions of
each of the three types of materials.
Metals
Most elements are metals. 88 elements to the left of the stairstep line are metals
or metal like elements.
Physical Properties of Metals:
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Luster (shininess)
Good conductors of heat and electricity
High density (heavy for their size)
High melting point
Ductile (most metals can be drawn out into thin wires)
Malleable (most metals can be hammered into thin sheets)
Chemical Properties of Metals:


Easily lose electrons
Corrode easily. Corrosion is a gradual wearing away. (Example: silver
tarnishing and iron rusting)
Nonmetals
Nonmetals are found to the right of the stairstep line. Their characteristics are
opposite those of metals.
Physical Properties of Nonmetals:
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No luster (dull appearance)
Poor conductor of heat and electricity
Brittle (breaks easily)
Not ductile
Not malleable
Low density
Low melting point
Chemical Properties of Nonmetals:

Tend to gain electrons
Since metals tend to lose electrons and nonmetals tend to gain electrons, metals
and nonmetals like to form compounds with each other. These compounds are
called ionic compounds. When two or more nonmetals bond with each other,
they form a covalent compound.
Metalloids
Elements on both sides of the zigzag line have properties of both metals and
nonmetals. These elements are called metalloids.
Physical Properties of Metalloids:
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Solids
Can be shiny or dull
Ductile
Malleable
Conduct heat and electricity better than nonmetals but not as well as
metals