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370
Democritus
Greece
Democritus found that;
• Everything is made of atoms
• Atoms cannot be broken
• Between atoms lies empty space
• Atoms are different in shape and size
• Atoms are constantly moving
Democritus gave us the basic information on the atom, which has resulted in many other discoveries. -
Isaac Newton
England -
Newton suggested that atoms were held together by certain forces.
Newton stated that we lived in a universe with small solid masses constantly in motion. -
John Dalton
England -
Dalton stated that the atoms of an element were the same as its weight, and atoms of different elements had different weights.
Dalton’s discoveries gave allowed us to understand valencies and how to calculate atomic weight. -
G J Stoney
England -
G. J. Stoney proposed that electricity was made of particles known as electrons although this theory was not confirmed until years later.
Stoney’s theory was confirmed by J.J. Thomson, and was considered a major discovery in science. -
JJ Thomson
UK -
Due to an investigation carried out by Thomson, he discovered electrons and positively charged ions.
His findings were the building blocks of the atom, and his discovery led to the ability of separating atoms and molecules according to their weight. -
Hantaro Nagaoka
Japan -
Nagaoka predicted that the nucleus of an atom was positively charged and that electrons orbited the nucleus.
Nagaoka’s theory was later proved by Ernest Rutherford. -
Robert A. Milikan
USA -
Milikan confirmed that electrons were a negative charge by suspending tiny oil droplets into an electric field.
His ideas concluded that all other charges were simple multiples of this basic charge -
Ernest Rutherford
New Zealand -
Rutherford experimented with alpha rays leading to the discovery and confirmation of the nucleus.
Rutherford discovery has provided the basis for the modern atomic structure. -
Henry Gwyn-Jeffreys Moseley
England -
He founded Moseley’s law that associated wavelength and atomic number. He also noticed gaps in the periodic table, and predicted elements missing.
Moseley discovery on atomic numbers has allowed us to determine the number of protons and element has. -
Niels Bohr
Denmark -
His idea was that the nucleus is made up of neutrons and protons, with the electrons revolving around the nucleus.
Bohr gave us the modern concept of the atomic model. -
James Chadwick
England -
He discovered that atoms contain neutral particles in its nucleus. Chadwick discovered neutrons.