World Builders™                                                                       Session One  --  Astronomy
   
The Periodic Table

The elements are made of tiny particles of matter caller protons, neutrons and electrons.
Elements that we find on other planets will be made of the same materials.

     People have wondered what the material world was actually made of. Were there millions of different kinds of materials, or were there building blocks of which everything else was made? The search for the elements was begun in ancient times. Elements are defined as substances which cannot be taken apart and broken into other, simpler substances. Substances made of a combination of elements are called compounds.

      It was difficult to find out which substances were elements. Water is plentiful, but it is made up of two gases, oxygen and hydrogen. Who would have guessed that? The air is made up of a mixture of different gases, but that is not obvious. As the science of chemistry developed, scientists discovered a number of ways to take compounds apart. However, it was difficult to see how their knowledge could be systematized.

      In the 19th century John Dalton, a British schoolmaster, showed that the elements always occurred in consistent proportions in specific compounds. This made it possible to make sense of the idea that matter was made of atoms. Elements can be parts of compounds that are very different from each other (oxygen is part of both water and rust) but they behave in consistent ways in their interactions with each other.

  The next advance came from weighing equal volumes of gases and comparing those weights against oxygen, which was given a weight of 16. The weights came out pretty close to whole numbers, which certainly provoked thought. The Russian chemist Dmitry Mendeleyev proposed arranging the elements in the order which we now call the Periodic Table. It arranges the atoms of the elements by weight. The vertical rows group elements which have similar properties.

      Although over a hundred elements have been identified, the largest atoms are unstable (radioactive) and tend to break apart. As it turns out, atoms are thought to be made of smaller parts: protons, neutrons, and electrons. Each element has its own number of each of these little building blocks. Because of this regularity, it is reasonable to believe that matter all over the universe will be made of the same elements that we have here. These elements will form familiar compounds -- everywhere.  

Click on a Symbol to Learn About the Elements. Can you find some that you are familiar with?


Periodic Table of the Elements
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac Unq Unp Unh Uns Uno Une
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Name Number Weight
The Solid Melts   The Liquid Boils
liquid at these temperatures

Legend

Metals

A solid substance that is a good conductor of heat and electricity. Can be formed into many shapes.

Metalloid

"Middle elements" - conduct heat and electricity better than nonmetals, but not as well as metals. Easier to shape than nonmetals, but not as easy as metals. Solid at room temperature.

Nonmetals

A poor conductor of heat and electricity. Not easily formed into shapes.

Author: Matthew Hoesch (mdih@msn.com) Free JavaScripts provided by The JavaScript Source  


          Some Examples of Elements from The Periodic Table

     You can look up these elements on the Periodic Table. Which element is the heaviest? At what temperatures will these elements boil? How cold must it be before they solidify (freeze)?

Symbol Name of Element state on earth
Atomic Weight
Remarks
H Hydrogen gas
1
Essential part of water, smallest atom
He Helium gas
4
another light weight gas
C Carbon solid
12
We are carbon based life forms
N Nitrogen gas
14
78% of our atmosphere
O Oxygen gas
16
Essential part of water: we breathe it
Si Silicon solid
28
Important component of rocks
Fe Iron solid
56
Abundant metal
Cu Copper solid
63.5
Familiar metal
Ag silver solid
108
Familiar metal
Sn Tin solid
118.7
Familiar metal
Au Gold solid
197
Precious metal
Pb Lead solid
207
Familiar metal

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© 1998, 2003. Elizabeth Anne Viau. All rights reserved. This material may be used by individuals for instructional purposes but not sold. Please inform the author if you use it at eviau@earthlink.net