Dalton in 1808 1904 1911 1540( 1808, 1904, 1911, 1540 ) said that atoms of the same compounds elements systems protons( compounds, elements, systems, protons ) had identical properties and those of similar the same metallic different( similar, the same, metallic, different ) elements are different. Dalton Rutherford Thomson Bohr( Dalton, Rutherford, Thomson, Bohr ) in 1904, designed an atomic model where electrons neutrons protons nucleus( electrons, neutrons, protons, nucleus ) were incrusted in a neutral negative circular positive( neutral, negative, circular, positive ) sphere. Rutherford in 1904 1911 1915 1880( 1904, 1911, 1915, 1880 ) drew an atomic model were the nucleus had got almost all the charge clouds electrons mass( charge, clouds, electrons, mass ) of the atom and all the positive negative neutral espherical( positive, negative, neutral, espherical ) charge, and he added protons electrons neutrons elements( protons, electrons, neutrons, elements ) in an electron cloud where it was located the positive neutral whole negative( positive, neutral, whole, negative ) charge. In 1913 Rutherford Bohr Thomson Dalton( Rutherford, Bohr, Thomson, Dalton ) specified the orbits roads droplets thickness( orbits, roads, droplets, thickness ) in the electron cloud and he detailed how protons things electrons neutrons( protons, things, electrons, neutrons ) moved in them.

The periodic table contains 119 117 118( 119, 117, 118 ) elements ordered by their atomic mass electronical( atomic, mass, electronical ) number. The system is divided into:
- eight seven nine( eight, seven, nine ) rows called periods groups families( periods, groups, families )
- eighty seventeen eighteen( eighty, seventeen, eighteen ) columns, called periods groups places( periods, groups, places ) or families. Elements which belong to the same group have got different electrical similar( different, electrical, similar ) chemical properties.
We can distinguish four general types of elements:
- Metals Non metals Semimetals( Metals, Non metals, Semimetals ): They are electricity and heat conducted. They are in liquid gas solid( liquid, gas, solid ) state except Mercury.
- Semimetals: Their behaviour is metallic bright important( metallic, bright, important ) or non bright special non metallic( non bright, special, non metallic ) depending on the conditions.
- Non-metals Noble gases Semimetals( Non-metals, Noble gases, Semimetals ): They are heat and electricity bad conducted. They are in solid, gas and liquid state.
- Especial gases Noble gases King gases( Especial gases, Noble gases, King gases ): They do not combine with other chemical elements.