Big Bang

Table

Under normal conditions of pressure and température :

the elements whose atomic number is rouge is Gaz them;
the elements whose atomic number is bleu is Liquide S (it has only two of them there: the Bromine and the mercury);
the elements whose atomic number is noir is solid S.

In the nature :

History

The first true version of this table, incomplete because all the elements were not known yet, was created by the Russian Dimitri Ivanovich Mendeleïev in 1869. The first classification had already been carried out before by Lothar Meyer in 1864, but this one comprised only 28 elements, those Ci being classified only by valence alone. Moreover, Meyer did not think of predicting other elements and of correcting the atomic weight starting from this table.

Mendeleïev noticed that certain properties varied in a periodic way with the Atomic mass. Thus, instead of classifying all the elements on the same column, it classified them on 5 columns of 18 elements (its table was vertical, today it is horizontal, the number of lines and of columns is thus reversed), by leaving empty boxes, expect that other elements would be later discovered.

In 1913, classification evolves/moves: one realizes that if one takes account of the chemical properties of the natural elements, the elements should not be classified according to the atomic masses but according to the numbers of load (atomic numbers, noted Z).

Note

This table is known as periodical because all the Atome S located in the same column (from 1 to 18), present close chemical properties. For example: in column 1, the Lithium Li and the Sodium Na have a chemical behavior near.

The explanation of this behavior rests on the fact that the number of electron S of their Couche of valence (all electrons present in addition to the configuration of last rare gas) is identical. Li and Na have only one electron of valence. It is this external electron which will be available for the chemical reactions with other atoms. From where close chemical properties and consequently their regrouping.

The atoms are grouped in:

metals: on the left
non-metals: on the right
Metalloid S: between the two precedents (B, If, Ge, Ace, Sb, Te, Po)
poor metals between metalloids and metals of transition (Al, Ga, In, Sn, Tl, Pb, Bi).
the metals of transition (columns 3 to 12)
the Lanthanide S: Z = 57 to 71
the Actinides: Z = 89 to 103

Certain elements of the same column received names:

1: alkaline Metals
2: alkaline-earth Metals
14: Cristallogène S
15: Pnictogène S
16: Chalcogène S
17: Halogenous S
18: Rare gas S

The higher the Atomic number Z (many protons) is, the more the cores are large. The more report/ratio N/Z (many neutrons on many protons) is far from the curve of stability, the more the core is unstable: it will emit particles to approach the stable values. It is said that it is radioactive.

In the periodic table, the atoms whose no Isotope is stable are:

the Technetium (Z=43);
the Promethium (Z=61);
all elements starting from the Polonium thus with Z equal to or higher than 84.

Certain predicted elements were never yet observed. Some their properties, but are supposed unknown. This is why the chemical series, represented by colors on the table, can appear in clearer. It is the case of:

Ununseptium

Means memotechnic

See the section " periodic Table of the elements "

See too

chemical Element
Table of the isotopes
wide Version of the periodic table of the elements
periodic Table of the elements detailed

External bonds

the periodic table of the elements, on the site of the City of Sciences (Site entirely in Flash)
periodic table on the site of the Faculty of Technology and Chemistry of Split (Croatia).

Be-X-old: Перыядычнаясістэмаэлементаў Roa-tared: Portale: Chìmeche Simple: Periodic counts Zh-yue: 元素週期表

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