Wikijunior:The Elements/Introduction to The Elements< Wikijunior:The Elements
Introduction to The ElementsEdit
The whole universe is built of matter. Right now, you are surrounded by it. The air we breathe is matter, and all the things you see around you are matter. The odors you smell are matter and the sounds you hear are caused by the movement of matter in your ears.
Matter is everything that takes up space and has weight. Scientists say that matter has volume and mass. Matter is made up of tiny building blocks called atoms. The purest type of atom is called an element. The elements are what give matter its different qualities.
Today we can see atoms by using a special instrument called an electron microscope. An electron microscope lets us see things that are millions of times smaller than the things we can see with a powerful optical microscope.
Most of the matter around us has more than one element in it. But some matter is made up of just one element. If you have ever held a diamond, for example, it is made of just one element, Carbon. Surprisingly, the graphite in a pencil that you use for drawing or writing is also Carbon, just its atoms are differently arranged.
Some other examples of matter that contain just one element are:
- An aluminium drink can
- 24 carat gold
- The helium gas in a balloon that floats upwards
- Cast iron garden railings
- Lead sheeting used by builders on the roofs of houses
NOTE: These examples are not truly pure elements, because metals will always have tiny amounts of other elements present as impurities.
Not many elements occur as a pure substance. Some elements like Gold and Sulphur do naturally occur as a pure substance, as does Carbon when it is a diamond. But most substances are made up of several elements bonded together. For example, water has the chemical formula H2O meaning that one molecule of water is composed of two hydrogen atoms and one oxygen atom.
Ancient people knew how to extract the element iron from iron oxide. They heated iron oxide dug from the ground with charcoal. The iron was originally a "compound" of two elements, iron and oxygen. By heating them, they separated. The oxygen joined with the carbon in the charcoal leaving the purified iron behind.
The Periodic Table of Elements is a table showing the different kinds of elements arranged according to their different characteristics. Much of it was worked out many years ago. So far we have identified 90 elements that occur naturally. There are approximately 25 more that are man-made.