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Lesson 1:

What’s the world made of?

Everything around us, from the leaves of trees to the stars, to your computer, is made up of tiny particles called atoms. You can say that atoms are like the bricks with which the whole universe is built.

Due to its small size, there is a huge number of atoms in every small portion of matter. Both solids, liquids and gases are made up of atoms, the main difference between one and another is how close they are in each case. In the air, for instance, atoms are much more separated than in the chair where you are seated right now. For this reason, if you punch in the air you will not get hurt, while if you punch in the chair the result will be quite different.

Even so, the great number of atoms of the air is hardly imaginable. Think of a small cube like the one on the right, 1mm on a side. Well, if that cube were filled with air, more than 5.000 billions (millions of millions) of atoms would fit in it.

How many different types of atoms exist?

You may wonder why there are so many differences between some things and others if they are all made up of atoms. One of the reasons is, as we have already seen, how close the atoms are inside an object. But, apart from that, the main reason is that there are more than 100 different types of atoms, and each one of them has different characteristics. All the atoms that have been discovered so far are compiled in the so-called periodic table:

The periodic table (click on it to see it in detail).

As you can see, there are oxygen atoms (O), iron atoms (Fe), helium atoms (He), gold atoms (Au)… And each of them has its own abbreviation.

You may also wonder why water or air atoms do not appear in the periodic table?

The reason is simple, both water and air are a mixture of several types of atoms. water, for example, is a mixture of hydrogen (H) and oxygen (O) atoms; while air is a mixture of nitrogen (N) and oxygen (O) atoms mainly.


It is true that atoms are very very small, however they are made up of other even smaller particles. Their names are:

  • Protons
  • Neutrons
  • Electrons

Protons and neutrons are together in the center of the atom in what is called the nucleus. Meanwhile, the electrons move at high speed around the nucleus.

The number of protons, neutrons and electrons is what differentiates one atom from another. For example, while a hydrogen atom is made up of only one proton and one electron turning around it, a gold atom is made up of 79 protons and as many neutrons and electrons.

But, why are we talking about all this in technology?

For one single reason, everything that is going to be explained from now on in this unit has a great relationship with one of the particles that atoms are made of:

¡the electrons!

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