Atomic theory

Events

demicratus

430

proposed first idea of atom; building blocks of matter; made up of tiny indestructable sub atomic particles called atomos

Lavoirse

1788

Law of conservation of mass:
matter cannot be created or destroyed only rearranged

proust

1794

Law of conservation of mass:
matter cannot be created or destroyed only rearranged

Gay-Lussac

1804

Law of combining Volumes:
at constant temperatures and pressure,
volumes of reacting gases and
gaseous products are in the ratio of small whole numbers

John Dalton

1811

Law of multiple proportions:
Same two elements can combine in different
Compounds; ratio of first element fixed, while the
Second element varies

Proposed first Atomic Theory

  1. All matter is made of tiny indivisible atoms
    1. Atoms of the same element are the same
    2. Atoms of different elements are different
    3. Atoms combine in whole number

Amedo Avagardo

1811

Avogardo's hypothesis-
equal volumes of gases, under the same conditions have the same number of particles (6.02x1023)

Wilhelm Rognten

1894

discovered x rays

Henri Bequerrel

1896

discovered that uranium emits radiation resembeling that of X-Rays

JJ Thompson

1897

used cathode rays to measure the bending of the rays to determine the charge to mass ratio of the electron
modified cathode rays were used to dicover the positivly charged neutron
plum pudding model

max planck

1900

Quantum theory:
energy is not emited constantly, but instead in small quantities called quanta

Albert Einstein

1905

Photoelectric effect;
when light of a certain frequency shines on a certain metal electrons are emitted

Ernest Rutherford

1911

studied substances especially the alpha particle conducted gold foil experiment: he bombarded gold foil with alpha particles most particles passed through he concluded that the atom is mostly empty space with a very small positively charged nucleus
nuclear model

Niels Bohr

1913

improved upon the atomic model by asking the question: why arent electrons puled into the nucleus
electrons energy increases as the distance from the nucleus increses
elctrons in each orbit have a certain amount of energy
when quatum leap happens the electron becomes to powerful for its orbit which causes the electron to jump from orbit to orbit without passing through the spaces in between

debroli

1923

if particles can act like waves, then waves can act like particles

Schrodinger

1926

Schrodingers wave equasions
treat the electron like a wave
developed an equation used to determine the probability of finding an electron in any given place around the nucleus

heisenberg

1927

it is impossible to know the velocity and position of an electron at the same time