john dalton was finder of the atomic theory. the theory propose that all matter was composed of atoms. atoms are the smallest particle of a chemical element that can exist. indivisible and indestructible building blocks.
my fascination with gases gradually led me to proper that every form of matter was also made up of small individual particle. i reference my work based on a greek philosopher Democritus of Abider's more abstract theory of matter, which centuries ego have been forgotten.
i created the first chart of atomic weights in 1803. since then, i became the first scientist to explain the behaviour of atoms in terms of measurement of weight.
j.j. Thomson discovered that all atoms contain tiny negatively charged subatomic particles or electrons.
my discovery were gradually accepted by scientist. the discovery was disproved the part of daltons atomic theory that assumed atoms were indivisible
i was experimenting with cathode ray tubes, and it showed me that all atoms carry small negatively charged subatomic particles or electrons.
plum pudding model
Rutherfords model shows that an atom is mostly empty space. with electrons orbiting a fixed, positively charged nucleus in set, predictable path
i was overturning Thomas's model with my well known gold foil experiment which i clearly demonstrate that the atom has a tiny and heavy nucleus. in my experiment, the positive alpha particles mostly passed trough the foil, but some bounced back.
in 1913, Niels Bohr proposed a theory that energy is transferred only in certain well defined quantities. electrons should move around the nucleus but only in prescribed orbits. a light quantum is emitted when jumping from one orbit to another with lower energy.
i spotted a problem in Rutherford theory so i decided to dig deeper. i knew that any charged particle that is moving is going to be giving off electromagnetic radiation as the wavelength of the radiation is going to vary.
James Chadwick discovered the neutron in atoms. the location of a neutrons are located in the center of an atom, in the nucleus along with the protons. they have no positive or negative charge.
i started with beryllium atoms with alpha particles. an unknown radiation was produced. i interpreted this radiation as being composed of particles with a neutral electrical charge and this particle is known as the neutron.