The atoms can be due to their mutual interaction behavior, because of their chemical properties, subdivided into elements. For all chemical processes is just a rearrangements of electrical distribution between the reaction partners. For the behavior of the elements is therefore the number of electrons, they want to bind itself, decisive. This is due to the charge of the nucleus as multiples of the number of protons it contains.

The classification of the elements is therefore with the size of the cargo nucleus. The mass of the nucleus, it plays for the chemical bond virtually no role. Atoms with the same atomic number but different mass (nuclei with the same number of protons but different number of neutrons) have the same element name, they called isotopes of that element.

In the periodic table of elements are the atomic sites with ascending atomic number registered with the observation will be taken into account that certain chemical properties are periodically repeated.

It makes the division into eight main categories, through the outer columns of the periodic table are represented. All elements in one of these columns have the same number of electrons in the outer shell (valence). The individual lines of the display is called the periods. They show how many shells in an item are occupied. There are a total of seven.


Figure 2: The Periodic Table of Elements

The simplest element is the hydrogen. He has a Hüllelektron the bottom bowl sits. As an exception when it is already helium with two electrons fully occupied. That is also the reason why helium in the 8th Major classified. During the next element, lithium, the next shell occupied in turn sits only one electron, so that the assignment again in the 1st Major falls.

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