Democritus, 380 BC, Abdera, GreeceIdeas & experiments:
-Matter was composed of tiny particles called atoms.
-They could join up with other atoms to create more atoms. Contribution to our understanding of the atom:
-Brought up the idea that atoms exist. Sources:
Period: 380 to
Discovery of the atom
Isaac Newtown,1704,Lincolnshire, EnglandIdeas & experiments:
-Proposed a mechanical universe with small solid masses in motion. Contribution to our understanding of atoms:
-atoms are held together by attractions that we call forces. Sources:
John Dalton, 1803, Cumberland, EnglandIdeas & experiments:
1. All matter is composed of tiny particles called atoms.
2. Atoms can’t be broken into smaller particles.
3. Atoms of the same element are alike.
4. Atoms join together in fixed ratios. Contributions to our understanding of the atom:
-all matter is composed of tiny particles called atoms.
- atoms of the same element are alike. Sources:
-Heinemann Interactive Science 3
George Johnstone Stoney, 1894, Oak Park, IrelandIdeas & experiments:
-Discovered electron- ‘atom of electricity’
-the Stoney scale Contribution to our understanding of the atom:
- discovered negative charge. Sources:
Joseph John Thomson, 1897, Manchester, EnglandIdeas & experiments:
-‘Plum pudding theory’
-discovery of the electron and of isotopes Contributions to our understanding of atoms:
-Atom is made up of a positively charged particle with tiny electrons scattered throughout the atom like raisins in a plum pudding. Sources:
Mark Planck, 1900, GermanyIdeas & experiments:
-used the idea of quanta (discrete units of energy) to explain hot glowing matter.
-created Planck’s constant
-created Planck’s Law of Black-body Radiation Contribution to our understanding of the atom:
-Revolutionised our understanding of atomic and subatomic processes Sources:
Hanatora Nagaota, 1903, Omura, JapanIdeas & experiments:
-‘Planetary model of atoms’- electrons revolving around the nucleus, bound by electrostatic forces. Contribution to our underdtanding of the atom:
- Created a slightly incorrect model of an atom based on the solar system, whiched improved our understand of the stucture of atoms. Sources:
Robert Andrews Milikan, 1909, AmericaIdeas & experiments:
-‘Milliken oil drop experiment’- Successfully measured the charge of a single atom (1.60 x 10-19 coulombs) Contributions to our understanding of the atom:
-allowed us to measure the charge to mass ratio of an electron. Sources:
Ernest Rutherford, 1911, Britian & New ZealandIdeas & experiments:
-Atom contained a dense nucleus containing all its positive charge. Contributions to our understanding of the atom:
-Electrons could orbit a positively charged nucleus, like planets orbiting a sun. Sources:
Henry Gwyn-Jeffreys Moseley, 1914, EnglandIdeas & experiments:
-Each nucleus was characterised by an atomic number, equal to the number of unit positive charges associated with it.
-Moseley Law that is an empirical law concerning the characteristic x-rays that are emitted by atoms Contributions to our understanding of the atom:
-By rearranging the periodic table according to atomic number rather than atomic weight, a more systematic arrangement was obtained. Sources:
Niels Bohr, 1922, DenmarkIdeas & experiments:
-‘Shell model’- Electrons could circle a nucleus without radiating energy only in orbits.
-the liquid drop model of the atomic nucleus Contribution to our understanding of the atom:
-developed an explanation of atomic structure that underlies regularities of the periodic table of elements. Sources:
James Chadwick, 1932, EnglandIdeas & experiments:
-Discovered neutrons Contribution to our understanding of the atom:
- Discovered negative charge in atoms. Sources: