September 1, 2021
Chemistry
Democritus (philosopher)
1st know proposal of the atomic theory
John Dalton
1808 Atomic theory, extended Democritus’ theory also he had proof.
Mendeleev
The periodic table
J.J Thomson
1897 discovery of the electron (electron has never been split) The plum pudding model.
Ernest Rutherford
1911 Discover of nucleus
Niesl Bohr
1913 The Bohr model of nucleus
James Chadwick
1932 Discovery of neutron
September 2, 2021
Atom is the smallest particle of an element to retain the identity of the element.
 It consists of the center piece, the nucleus surrounded by electron with different
energy levels.
 Nucleus is made up of proton and neutron
 Neutron has 99.9% of the mass of the whole atom
 Most of the atom is an empty space 10-10 m
 If nucleus was an apple the electron would be a kilometer away
 Atom is same scale to a pea like pea is to earth
Alpha Particles are made out of helium nucleus