All elements are composed of atoms; atoms are particles. Atoms of the same element are exactly alike and if they are different they do not look alike.
Compounds are formed by the making of atoms from different elements.
In 1803, John Dalton, an English chemist, introduced an early atomic theory of matter.
I studied how electricity moved through a gas filled pipe, to which I found that light was made. I placed a magnet around the cathode ray tube causing the light beam to bend.
I found out that electrons were also negatively charged. My atomic model is named the “plum pudding” model.
In 1897, J.J. Thomson, an English physicist, discovered negatively charged electrons using a cathode ray tube.
The actual results showed a number of particles repelled at almost 180 degrees off of the foil while most passed straight through the foil.
I fired a stream of tiny positively charged alpha (helium) particles at a very thin sheet of gold foil. He predicted that the particles would move just a few degrees from their paths as they all passed through.
In 1908, Ernest Rutherford, a New Zealand-born English physicist, conducted his gold foil experiment. He discovered the positively,the nucleus, as well as discovered positively charged protons. Rutherford determined that atoms were mostly empty space.
I had been puzzled that the particle collisions produced heavier nuclei yet their positive charges remained the same. I have concluded the particles came from the bombarded nuclei and that contained no charge. They're neutral!
James Chadwick, a student of Rutherford’s, discovered neutral (“no charge”) neutrons in the nucleus of an atom. His proton-neutron model is still accepted today.
My atomic model is called the “planetary model.”
In 1913, Niels Bohr, a Danish physicist, said that electrons were located in specific energy levels and that electrons traveled in definite orbits around the nucleus.