Karteikarten
Early ideas about the composition of matter
Karten in diesem Stapel (10)
- 1Democritus 460-370BCEproposed that matter was made up of particles that cannot be divided futher
- 2Aristotle 384-322BCEproposed elements ware made up of earth, air, wind and fire
- 3Robert Boyle 1627-1691believed that matter was made up of tint particles that cannot be subdivided- these are made from compounds.
solids have fixed particles but liquid and gas have free moving particles. - 4John Dalton 1766-1844named particles 'atoms'.
believed every atom had its own atomic weight and can react together to from molecules.
particles that are identical have the same mass and chemical properties. - 5Eugen Goldstein 1850-1930discovered that cathode rays contains negatively charged particles with mass, cathode rays could be split and heavier positive particles
- 6Joseph John Thompson 1856-1937discovered that atoms have electrons, that they have a very small mass and that they are negatively charged.
(plumb pudding model) - 7Ernest Rutherford 1871-1937thought that the mass of an atom is not evenly spread and that there is a nucleus and that the nucleus is positively charged and that the electrons circulate the rest of the atom.
decided atomic number corresponds to the elements position in the periodic table. - 8Henry Moseley 1888-1915along with Ernest Rutherford, decided atomic number corresponds to the elements position in the periodic table.
only discovered that half the mass of an atom is made from the proton. - 9James Chadwick 1891-1974identified a neutron and that they have no charge but have the same mass as a proton.
- 10Niels Bohr 1885-1962discovered that electrons orbit the nucleus in energy levels. energy levels have fixed energy values and electrons can only occupy these set values.