The essential atomic structure consists of the nucleus together with the protons (positively charged) and the neutrons (electrically neutral) as well as the electrons (negatively charged).
1836 electrons together form the matter of a proton or a neutron, respectively, i.e. almost the whole matter of an atom is concentrated in the nucleus.
Using the quantum theory the probability of the occurrence in the atomic shell (orbital) can be determined for every electron. Therefore, the atomic shell can be explained as the distribution of the electron density and not, like according to the theory by Bohr, as an arrangement of electrons moving on exactly determined paths. The orbitals can be imagined as a scattered cloud whose dimension and shape are defined for every electron.
According to quantum mechanics the atomic shell is understood as a system of permitted energy levels. This means that the electrons are allowed to adopt defined energy values only. These permitted energy steps are classified according to a defined scheme that is described using the quantum numbers. It is distinguished between the main quantum number, orbital quantum number, magnetic quantum number and spin quantum number.
According to the Pauli principle the number of atoms defined by the ordinal number Z is distributed to these energy levels. This principle states that in one atom or atomic union two electrons must not correspond to each other in either of the four quantum numbers.
Using the electron configuration the chemical, electrical and magnetic properties of the elements can be explained.
Magnitude of the atoms:
- Nucleus diameter Æ: = 10-15 m,
- Shell diameter » 10-10 m,
This means – an atom having a diameter of 5 m would have a nucleus diameter of 0.05 mm.
A piece of nucleus matter of the size of a pin head would have the mass of 10,000 t.
If all of the natural and artificially generated elements according to a higher relative atomic matter are arranged in such a way that chemically relative elements are one below the other, the periodic system of the elements will result. The sequence of the elements is determined by the ordinal number Z that is identical to the number of protons or electrons of the elementary atoms, respectively. In a suitably arranged periodic system the structure of the atomic shells belonging to the individual elements can be seen directly.