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John Dalton - 1808
John Dalton created the very first atomic theory. Dalton viewed atoms as tiny, solid balls. His atomic theory had 4 statements…
1. Atoms are tiny, invisible particles.
2. Atoms of one element are all the same.
3. Atoms of different elements are different.
4. Compounds form by combining atoms. -
J.J. Thomson (1897)
J.J. Thomson discovered electrons. He also proposed the
existence of a (+) particle. His atomic model was known
as the “raisin bun mode." Atoms are made mostly out of (+) charged material, like dough in a bun. The (-) charged electrons are found inside the (+) dough. -
Ernest Rutherford (1911)
Rutherford discovered protons and the nucleus. He called these (+)
particles protons. He called the centre of atoms the nucleus. -
Niels Bohr (1913)
Niels Bohr improved on Rutherford’s model. Every atom has a
specific number of electron shells. -
James Chadwick (1932)
Chadwick discovered neutrons. He called these particles neutrons. Neutrons are also found in the nucleus. -
Period: to
The Modern Model (1932-today)
Work done since 1920 has changed the model. It is impossible to
know where an electron is at any given time.
