Page 51 - 新思维科学学生用书7 样章

2 Materials and their structure

What are atoms?

Over 2000 years ago, a Greek philosopher called Democritus
suggested that everything was made up of tiny pieces.
Democritus suggested that, if you could keep on cutting up a

substance into smaller and smaller pieces, you would end up with
a very small piece that could not be cut up any more.

Democritus called his tiny pieces of matter atoms. Atom means
‘cannot be divided’.

We now know that atoms really do exist. Today we can
even see some of the large kinds of atom, using special Nanotubes

microscopes called scanning tunnelling microscopes. The
photograph shows the atoms in some carbon nanotubes. (Nano means ‘very, very small’.)

Different types of atom

There are many different types of atom. Scientists have discovered 94 different types of atom that occur
naturally in the universe. Another 24 kinds of atom have been made in laboratories.

Some substances are made up of just a single kind of atom. A substance made of just one kind of atom
is called an element. For example, carbon is made only of carbon atoms. Gold is made only of gold
atoms. Silver is made only of silver atoms. Carbon, gold and silver are examples of elements.

Each type of atom has different properties. This is why different elements have different properties.

If you could see some of the atoms in the silver ring, they
These rings are made from pure silver. would look something like this.

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