He belived that matter are made of small particles that cannot be divided, created or destroyed and nothing is between these except empty space. He called these particles "atomos"
384 BC - 322 BC
He did not belive that empty space exists. Instead, he favored the more popular idea -that all matter is made of fire, wáter, air, and earth.
1750 - 1914
1766 - 1844
He discovered that certain gases could only be combined in certain proportions, even if wo different compounds shared the same common element or group of elements
1776 - 1856
Avogadro was an Italian chemist whose hypothesis was that equal volumes of gases under the same conditions of pressure and temperatura contain the same number of particles. His work was ignored during his lifetime and after his dead his idea was accepted. Later physics and chemist determined the value of "Avogadro's Number", the number of gas molecules in one mole, as 6.02 x 1023.
1780 - 1849
German chemist who developed the Law of Triads in 1829 in an early attempt to classify the chemical elements.
1799 - 1815
1810 - 1821
1834 - 1907
He arranged the elements in a list using their atomic masses.
1837 - 1898
English chemist who in 1983 proposed the Law of Octaves which stated that chemical properties repeated with every eighth element.
J. J. THOMSON
1856 - 1940
He proposed that an atom was a sphere with a positive charge evenly spread througout. Negatively charge electrons were mixed through the positive charge.
BENITO JUAREZ GOVERNMENT
1867 - 1872
1871 - 1937
He concluded that atoms are made mostly of empty space, taht most of an atom´s mass and positive charge is concentrated in a small área in the center of the atom called the nucleus
1877 - 1911
1885 - 1962
in the mordern atomic model, electrons form an electron cloud. An elelctron cloud is an área around an atomic nucleus where an electron is most likely to be located.
1887 - 1915
He proposed that the properties of the elements varied periodically with atomic number.
1891 - 1974
He also researched atoms and discovered that, in addition to protons, the nucleus also contained neutrons