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Today we know that some substances on Earth are not mixtures. They are called elements. Gold is an element. No matter how you break up gold, all the pieces are still gold, even down to the tiniest pieces. Copper is another element. So are oxygen and helium. Ninety-two different elements are found naturally on Earth. Everything on Earth is made out of one or more of these elements.

For many centuries, people wondered how small the smallest piece of something could be. Scientists have given a name to the tiniest piece of an element. The tiniest piece is called an atom. Gold is made up of gold atoms, and copper is made up of copper atoms. Oxygen atoms make up the oxygen in the air we breathe. We use helium atoms to fill balloons. Atoms are so small that you can’t see them. It takes about 1 million copper atoms to make a tiny, visible piece of copper. It would take 39 million copper atoms side by side to make a line 1 cm long.

Scientists have put the 92 natural elements in order from the lightest to the heaviest. The first element is hydrogen. It is the lightest and the most common element in the universe. The Sun is made up mostly of hydrogen. On Earth, hydrogen is a gas. It is used as rocket fuel.

Element 2 is helium. It is the next lightest atom. Helium is also a gas. Because it is lighter than air, it is used to fill blimps and party balloons.

Element 8 is very important. It is oxygen. It is part of the solution we call air. Humans and other animals take in oxygen when they breathe. You need oxygen to stay alive. Nearly all organisms need it to survive.

Element 26 is iron. When you see red-colored hillsides or mountains, it is likely that they contain iron. People found that they could remove iron from the mixture of red dirt using heat. They could melt the iron and form it into different shapes. For many centuries, iron has been a very useful element for making tools.

Interesting stories can be told about each of the 92 elements. Each has been useful in some way to humans. Chemists study the elements. They study how elements can be combined and how elements and their combinations can be used. Chemists will have plenty to do for a long time, because there are many things still to be learned about elements.

Atom Symbols

People abbreviations or symbols to stand for thins or ideas. The names of states are represented by abbreviation. New York, for example, can be represented by the abbreviation NY. TX is the abbreviation for Texas. CA is the abbreviation for California. What is the abbreviation for the state in which you live?

Atoms are represented by symbols. O is the symbol for oxygen. N is the symbol for nitrogen. I is the symbol for iodine.

Some names of atoms begin with the same letters, so the same symbol cannot be used for both. This is why the hydrogen symbol is H, and the helium symbol is He. C is carbon, while Ca is Calcium.

In early times, Romans and Greeks used substances such as gold, silver, and iron to make art objects and tools. They used words in their own languages to name the substances. The Latin word for gold is aurum. Silver was called argentum. Iron was called ferrum. Today the atoms for these elements are given the symbols Au, Ag, and Fe.

Take some time to look at the periodic table that lists the 92 natural elements. See if you can find other symbols that come from Roman or Greek words.

PERIODIC TABLE Created by Amber N. 2007