UNDERSTANDING THE ATOM

Events

DEMOCRITUS

460 BC - 370 BC

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"

ARISTOTLE

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.

INDUSTRIAL REVOLUTION

1750 - 1914

JOHN DALTON

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

Amedeo Avogadro

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.

JOHANN DOBEREINER

1780 - 1849

German chemist who developed the Law of Triads in 1829 in an early attempt to classify the chemical elements.

NAPOLEONIC WARS

1799 - 1815

MEXICAN INDEPENDENCE

1810 - 1821

DIMITRI MENDELEEV

1834 - 1907

He arranged the elements in a list using their atomic masses.

JOHN NEWLANDS

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

ERNEST RUTHERFORD

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

PORFIRIATO

1877 - 1911

NIELS BOHR

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.

HENRY MOSELEY

1887 - 1915

He proposed that the properties of the elements varied periodically with atomic number.

JAMES CHADWICK

1891 - 1974

He also researched atoms and discovered that, in addition to protons, the nucleus also contained neutrons

MEXICAN REVOLUTION

1910 - 1921

WORLD WAR I

1914 - 1918

WORLD WAR II

1939 - 1945