Everything in our universe is built from atoms.
Scientists have calculated that there are about 1080 atoms in the universe. This is a large number, with 80 zeros.
There are also a lot of these tiny particles in your body: around 1027.
However, the body is made up of only 40 different types of atoms. We call these chemical elements. Among them, the most common are oxygen, carbon, hydrogen, nitrogen and calcium.
All together know 118 elements. Eighty-eight are found in nature, while others are produced in laboratories or nuclear reactors
The elements are arranged in a periodic system, which was developed by the Russian chemist Dmitri Ivanovich Mendeleev 150 years ago.
This is why we’re celebrating the International Year of the Periodic Table. There are events around the world that children and adults will take part in to mark this discovery.
Until March 1st you could, for example, take part in the preparation of the Mendeleev mosaic.
Mendeleev classified thirty-six of the known elements in the table in such a way that he put together those with similar properties: one side for metals, the other for gases.
Only 30 years later scientists discovered the structure of the atom, and that this determines the properties of the elements. Those that are made up of atoms with a similar number of protons have similar chemical properties.
Mendeleev also described in detail elements that had not yet been discovered. During his life, three of the empty spaces were filled with new ones. The most recent element was made artificially just four years ago. In the future we may discover or produce something else.
The symbols of the elements are the same throughout the world. We can also use only the initials (e.g. O for oxygen) or the initials and the second letter (e.g. He for helium). They come from many languages, but mostly from Latin and Greek.
Points to Consider
- Can you name a few more elements.
- Do you know any particles that are smaller than elements?
- Look closely at the periodic table. What else do you see?
The original version of this article was published on February 28th.